[Federal Register Volume 78, Number 132 (Wednesday, July 10, 2013)]
[Proposed Rules]
[Pages 41500-41547]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-16521]



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Vol. 78

Wednesday,

No. 132

July 10, 2013

Part II





Department of the Interior





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Fish and Wildlife Service





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50 CFR Part 17





Endangered and Threatened Wildlife and Plants; Threatened Status for 
the Northern Mexican Gartersnake and Narrow-headed Gartersnake; 
Proposed Rule

  Federal Register / Vol. 78 , No. 132 / Wednesday, July 10, 2013 / 
Proposed Rules  

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2013-0071; 4500030113]
RIN 1018-AY23


Endangered and Threatened Wildlife and Plants; Threatened Status 
for the Northern Mexican Gartersnake and Narrow-headed Gartersnake

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
list the northern Mexican gartersnake (Thamnophis eques megalops) and 
narrow-headed gartersnake (Thamnophis rufipunctatus) as threatened 
species under the Endangered Species Act of 1973, as amended (Act). If 
we finalize this rule as proposed, it would extend the Act's 
protections to these species. The effect of this regulation is to 
conserve northern Mexican and narrow-headed gartersnakes under the Act.

DATES: We will accept comments received or postmarked on or before 
September 9, 2013. Comments submitted electronically using the Federal 
eRulemaking Portal (see ADDRESSES section, below) must be received by 
11:59 p.m. Eastern Time on the closing date. We must receive requests 
for public hearings, in writing, at the address shown in the FOR 
FURTHER INFORMATION CONTACT section by August 26, 2013.

ADDRESSES: You may submit comments by one of the following methods:
    (1) Electronically: Go to the Federal eRulemaking Portal: http://www.regulations.gov. Search for Docket No. FWS-R2-ES-2013-0071, which 
is the docket number for this rulemaking. When you locate this 
document, you may submit a comment by clicking on ``Comment Now!''
    (2) By hard copy: Submit by U.S. mail or hand-delivery to: Public 
Comments Processing, Attn: FWS-R2-ES-2013-0071; Division of Policy and 
Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax 
Drive, MS 2042-PDM; Arlington, VA 22203.
    We request that you send comments only by the methods described 
above. We will post all comments on http://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see the Information Requested section below for more information).

FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor, U.S. 
Fish and Wildlife Service, Arizona Ecological Services Field Office, 
2321 West Royal Palm Road, Suite 103, Phoenix, AZ 85021; telephone: 
602-242-0210; facsimile: 602-242-2513. If you use a telecommunications 
device for the deaf (TDD), call the Federal Information Relay Service 
(FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

    Why we need to publish a rule. Under the Endangered Species Act 
(Act), if a species is determined to be an endangered or threatened 
species throughout all or a significant portion of its range, we are 
required to promptly publish a proposal in the Federal Register and 
make a determination on our proposal within one year. Listing a species 
as an endangered or threatened species can only be completed by issuing 
a rule. Elsewhere in today's Federal Register, we propose to designate 
critical habitat for the northern Mexican and narrow-headed 
gartersnakes under the Act.
    This document consists of:
     A proposed rule to list the northern Mexican and narrow-
headed gartersnakes as threatened species throughout their ranges, and
     A proposed special rule under section 4(d) under the Act 
that outlines the prohibitions necessary and advisable for the 
conservation of the northern Mexican gartersnake.
    The basis for our action. Under the Act, we can determine that a 
species is an endangered or threatened species based on any of five 
factors: (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) the inadequacy of existing regulatory 
mechanisms; or (E) other natural or manmade factors affecting its 
continued existence. In the case of the northern Mexican and narrow-
headed gartersnakes, we have determined that harmful nonnative species 
(spiny-rayed fish, bullfrogs, and crayfish), wildfires, and land uses 
that divert, dry up, or significantly pollute aquatic habitat have 
solely or collectively affected these gartersnakes, and several of 
their native prey species, such that their resiliency, redundancy, and 
representation across their ranges have been significantly compromised.
    We will seek peer review. We are seeking comments from 
knowledgeable individuals with scientific expertise to review our 
analysis of the best available science and application of that science 
and to provide any additional scientific information to improve this 
proposed rule. Because we will consider all comments and information 
received during the comment period, our final determinations may differ 
from this proposal.

Information Requested

    We intend that any final action resulting from this proposed rule 
will be based on the best scientific and commercial data available and 
be as accurate and as effective as possible. Therefore, we request 
comments or information from other concerned governmental agencies, 
Native American tribes, the scientific community, industry, or any 
other interested parties concerning this proposed rule. We particularly 
seek comments concerning:
    (1) The species' biology, range, and population trends, including:
    (a) Habitat requirements for feeding, breeding, and sheltering;
    (b) Genetics and taxonomy;
    (c) Historical and current range, including distribution patterns;
    (d) Historical and current population levels, and current and 
projected trends; and
    (e) Past and ongoing conservation measures for these species, their 
habitat or both.
    (2) The factors that are the basis for making a listing 
determination for these species under section 4(a) of the Act (16 
U.S.C. 1531 et seq.), which are:
    (a) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (b) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (c) Disease or predation;
    (d) The inadequacy of existing regulatory mechanisms; or
    (e) Other natural or manmade factors affecting its continued 
existence.
    (3) Biological, commercial trade, or other relevant data concerning 
any threats (or lack thereof) to these species and existing regulations 
that may be addressing those threats.
    (4) Additional information concerning the historical and current 
status, range, distribution, and population size of these species, 
including the locations of any additional populations of these species.
    (5) Any information on the biological or ecological requirements of 
these species, and ongoing conservation measures for the species and 
their habitats.
    (6) Any information on the projected and reasonably likely impacts 
of climate

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change on the northern Mexican gartersnake and narrow-headed 
gartersnake.
    Please include sufficient information with your submission (such as 
scientific journal articles or other publications) to allow us to 
verify any scientific or commercial information you include.
    Please note that submissions merely stating support for or 
opposition to the action under consideration without providing 
supporting information, although noted, will not be considered in 
making a determination, as section 4(b)(1)(A) of the Act directs that 
determinations as to whether any species is a threatened or endangered 
species must be made ``solely on the basis of the best scientific and 
commercial data available.''
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. We request 
that you send comments only by the methods described in the ADDRESSES 
section.
    If you submit information via http://www.regulations.gov, your 
entire submission--including any personal identifying information--will 
be posted on the Web site. If your submission is made via a hardcopy 
that includes personal identifying information, you may request at the 
top of your document that we withhold this information from public 
review. However, we cannot guarantee that we will be able to do so. We 
will post all hardcopy submissions on http://www.regulations.gov. 
Please include sufficient information with your comments to allow us to 
verify any scientific or commercial information you include.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on http://www.regulations.gov, or by 
appointment, during normal business hours, at the U.S. Fish and 
Wildlife Service, Arizona Ecological Services Field Office (see FOR 
FURTHER INFORMATION CONTACT).

Previous Federal Actions

    The northern Mexican and narrow-headed gartersnakes were placed on 
the list of candidate species as Category 2 species on September 18, 
1985 (50 FR 37958). Category 2 species were those for which existing 
information indicated that listing was possibly appropriate, but for 
which substantial supporting biological data to prepare a proposed rule 
were lacking. In the 1996 Candidate Notice of Review (February 28, 
1996; 61 FR 7596), the use of Category 2 candidates was discontinued, 
and the northern Mexican and narrow-headed gartersnakes were no longer 
recognized as candidates.
    On December 19, 2003, we received a petition from the Center for 
Biological Diversity (``petitioner'') dated December 15, 2003, 
requesting that we list the northern Mexican gartersnake as threatened 
or endangered, and that we designate critical habitat concurrently with 
the listing. The petition was clearly identified as a petition for a 
listing rule and contained the names, signatures, and addresses of the 
requesting parties. Included in the petition was supporting information 
regarding the species' taxonomy and ecology, historical and current 
distribution, present status, and actual and potential causes of 
decline. We acknowledged the receipt of the petition in a letter to the 
petitioner, dated March 1, 2004. In that letter, we also advised that, 
due to funding constraints in fiscal year (FY) 2004, we would not be 
able to begin processing the petition at that time.
    On May 17, 2005, the petitioner filed a complaint for declaratory 
and injunctive relief, challenging our failure to issue a 90-day 
finding for the northern Mexican gartersnake in response to the 
petition as required by 16 U.S.C. 1533(b)(3)(A) and (B). In a 
stipulated settlement agreement, we agreed to submit a 90-day finding 
to the Federal Register by December 16, 2005, and if substantial, 
submit a 12-month finding to the Federal Register by September 15, 2006 
(Center for Biological Diversity v. Norton, CV-05-341-TUC-CKJ (D. Az)). 
The settlement agreement was signed and adopted by the District Court 
of Arizona on August 2, 2005.
    On December 13, 2005, we made our 90-day finding that the petition 
presented substantial scientific information indicating that listing 
the northern Mexican gartersnake may be warranted; the finding and our 
initiation of a status review was published in the Federal Register on 
January 4, 2006 (71 FR 315).
    On September 26, 2006, we published a 12-month finding that listing 
of the northern Mexican gartersnake was not warranted because we 
determined that not enough information on the subspecies' status and 
threats in Mexico was known at that time (71 FR 56227). On November 17, 
2007, the petitioner filed a complaint for declaratory and injunctive 
relief pursuant to section 11 of the Act (16 U.S.C. 1540), seeking to 
set aside the 12-month finding. Additionally, a formal opinion was 
issued by the Solicitor of the Department of the Interior, ``The 
Meaning of In Danger of Extinction Throughout All or a Significant 
Portion of Its Range'' (U.S. DOI 2007), which provides further guidance 
on how to conduct a detailed analysis of whether a species is in danger 
of extinction throughout a significant portion of its range. In 
December 2007, the Service withdrew the September 26, 2006, 12-month 
finding in order to consider the new ``Significant Portion of the 
Range'' policy. In a stipulated settlement agreement with the 
petitioner, we agreed to submit a new 12-month finding to the Federal 
Register by November 17, 2008 (Center for Biological Diversity v. 
Kempthorne, CV-07-596-TUC-RCCJ (D. Az)). The settlement agreement was 
signed and adopted by the District Court of Arizona on June 18, 2008.
    On May 28, 2008, we published notice (73 FR 30596) of our intent to 
initiate a status review for the northern Mexican gartersnake and 
solicited the public for information on the status of, and potential 
threats to, this species.
    On November 25, 2008, we published a second 12-month finding that 
listing of the northern Mexican gartersnake was warranted but precluded 
by other listing priorities at that time (73 FR 71788). The petitioner 
described three potentially listable entities of northern Mexican 
gartersnake for consideration by the Service: (1) Listing the U.S. 
population as a distinct population segment (DPS); (2) listing the 
subspecies throughout its range in the United States and Mexico based 
on its rangewide status; or (3) listing the subspecies throughout its 
range in the United States and Mexico based on its status in the United 
States. Because we found that listing the northern Mexican gartersnake 
rangewide was warranted, there was no need to conduct any further 
analysis of the remaining two options, which are smaller geographic 
entities and are subsumed by the rangewide listing.

Status Assessments for Northern Mexican and Narrow-headed Gartersnakes

Background

Northern Mexican Gartersnake

Subspecies Description
    The northern Mexican gartersnake ranges in color from olive to 
olive-brown or olive-gray with three lighter-colored stripes that run 
the length of the body, the middle of which darkens towards the tail. 
It may occur with other native gartersnake species and can be difficult 
for people without specific expertise to identify. The snake may reach 
a maximum known length of 44 inches (in) (112 centimeters (cm)). The 
pale yellow to light-tan lateral (side of

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body) stripes distinguish the northern Mexican gartersnake from other 
sympatric (co-occurring) gartersnake species because a portion of the 
lateral stripe is found on the fourth scale row, while it is confined 
to lower scale rows for other species. Paired black spots extend along 
the olive dorsolateral fields (region adjacent to the top of the 
snake's back) and the olive-gray ventrolateral fields (region adjacent 
to the area of the snake's body in contact with the ground). The scales 
are keeled (possessing a ridge down the center of each scale). A more 
detailed subspecies description can be found in our September 26, 2006 
(71 FR 56227), or November 25, 2008 (73 FR 71788) 12-month findings for 
this subspecies, or by reviewing Rosen and Schwalbe (1988, p. 4), 
Rossman et al. (1996, pp. 171-172), Ernst and Ernst (2003, pp. 391-
392), or Manjarrez and Garcia (1993, pp. 1-5).
Taxonomy
    The northern Mexican gartersnake is a member of the family 
Colubridae and subfamily Natricinae (harmless live-bearing snakes) 
(Lawson et al. 2005, p. 596). The taxonomy of the genus Thamnophis has 
a complex history, partly because many of the species are similar in 
appearance and arrangement of scales, but also because many of the 
early museum specimens were in such poor and faded condition that it 
was difficult to study them (Conant 2003, p. 6).
    Prior to 2003, Thamnophis eques was considered to have three 
subspecies, T. e. eques, T. e. megalops, and T. e. virgatenuis (Rossman 
et al. 1996, p. 175). In 2003, an additional seven new subspecies were 
identified under T. eques: (1) T. e. cuitzeoensis; (2) T. e. 
patzcuaroensis; (3) T. e. insperatus; (4) T. e. obscurus; (5) T. e. 
diluvialis; (6) T. e. carmenensis; and (7) T. e. scotti (Conant 2003, 
p. 3). Common names were not provided, so in this proposed rule, we use 
the scientific name for all subspecies of Mexican gartersnake other 
than the northern Mexican gartersnake. These seven new subspecies were 
described based on morphological differences in coloration and pattern; 
have highly restricted distributions; and occur in isolated wetland 
habitats within the mountainous Transvolcanic Belt region of southern 
Mexico, which contains the highest elevations in the country (Conant 
2003, pp. 7-8). The validity of the current taxonomy of the 10 
subspecies of T. eques is accepted within the scientific community. A 
more detailed description of the taxonomy of the northern Mexican 
gartersnake is found in our September 26, 2006 (71 FR 56227) and 
November 25, 2008 (73 FR 71788) 12-month findings for this subspecies. 
Additional information regarding this subspecies' taxonomy can be found 
in de Queiroz et al. (2002, p. 323), de Queiroz and Lawson (1994, p. 
217), Rossman et al. (1996, pp. xvii-xviii, 171-175), Rosen and 
Schwalbe (1988, pp. 2-3), Liner (1994, p. 107), and Crother et al. 
(2012, p. 70).
Habitat and Natural History
    Throughout its rangewide distribution, the northern Mexican 
gartersnake occurs at elevations from 130 to 8,497 feet (ft) (40 to 
2,590 meters (m)) (Rossman et al. 1996, p. 172) and is considered a 
``terrestrial-aquatic generalist'' by Drummond and Marc[iacute]as-
Garc[iacute]a (1983, pp. 24-26). The northern Mexican gartersnake is a 
riparian obligate (restricted to riparian areas when not engaged in 
dispersal behavior) and occurs chiefly in the following general habitat 
types: (1) Source-area wetlands (e.g., cienegas (mid-elevation wetlands 
with highly organic, reducing (basic or alkaline) soils), or stock 
tanks (small earthen impoundment)); (2) large-river riparian woodlands 
and forests; and (3) streamside gallery forests (as defined by well-
developed broadleaf deciduous riparian forests with limited, if any, 
herbaceous ground cover or dense grass) (Hendrickson and Minckley 1984, 
p. 131; Rosen and Schwalbe 1988, pp. 14-16). Emmons and Nowak (2013, p. 
14) found this subspecies most commonly in protected backwaters, 
braided side channels and beaver ponds, isolated pools near the river 
mainstem, and edges of dense emergent vegetation that offered cover and 
foraging opportunities when surveying in the upper Verde River region. 
Additional information on the habitat requirements of the northern 
Mexican gartersnake within the United States and Mexico can be found in 
our 2006 (71 FR 56227) and 2008 (73 FR 71788) 12-month findings for 
this subspecies and in Rosen and Schwalbe (1988, pp. 14-16), Rossman et 
al. (1996, p. 176), McCranie and Wilson (1987, pp. 11-17), Ernst and 
Ernst (2003, p. 392), and Cirett-Galan (1996, p. 156).
    The northern Mexican gartersnake is surface active at ambient (air) 
temperatures ranging from 71 degrees Fahrenheit ([deg]F) to 91 [deg]F 
(22 degrees Celsius ([deg]C) to 33 [deg]C) and forages along the banks 
of waterbodies (Rosen 1991, p. 305, Table 2). Rosen (1991, pp. 308-309) 
found that northern Mexican gartersnakes spent approximately 60 percent 
of their time moving, 13 percent of their time basking on vegetation, 
18 percent of their time basking on the ground, and 9 percent of their 
time under surface cover; body temperatures ranged from 75 to 91 [deg]F 
(24 to 33 [deg]C) and averaged 82 [deg]F (28 [deg]C), which is lower 
than other, similar species with comparable habitat and prey 
preferences. Rosen (1991, p. 310) suggested that lower preferred body 
temperatures exhibited by northern Mexican gartersnakes may be due to: 
(1) Their tendency to occupy cienega-like habitat, where warm air 
temperatures are relatively unavailable; and (2) their tendency to 
remain in dense cover. In the northern-most part of its range, the 
northern Mexican gartersnake appears to be most active during July and 
August, followed by June and September.
    The northern Mexican gartersnake is an active predator and is 
believed to heavily depend upon a native prey base (Rosen and Schwalbe 
1988, pp. 18, 20). Northern Mexican gartersnakes forage along vegetated 
banklines, searching for prey in water and on land, using different 
strategies (Alfaro 2002, p. 209). Generally, its diet consists of 
amphibians and fishes, such as adult and larval (tadpoles) native 
leopard frogs (e.g., lowland leopard frog (Lithobates yavapaiensis) and 
Chiricahua leopard frog (Lithobates chiricahuensis)), as well as 
juvenile and adult native fish species (e.g., Gila topminnow 
(Poeciliopsis occidentalis occidentalis), desert pupfish (Cyprinodon 
macularius), Gila chub (Gila intermedia), and roundtail chub (Gila 
robusta)) (Rosen and Schwalbe 1988, p. 18). Drummond and 
Marc[iacute]as-Garc[iacute]a (1983, pp. 25, 30) found that as a 
subspecies, Mexican gartersnakes fed primarily on frogs. Auxiliary prey 
items may also include young Woodhouse's toads (Anaxyrus woodhousei), 
treefrogs (Family Hylidae), earthworms, deermice (Peromyscus spp.), 
lizards of the genera Aspidoscelis and Sceloporus, larval tiger 
salamanders (Ambystoma tigrinum), and leeches (Gregory et al. 1980, pp. 
87, 90-92; Rosen and Schwalbe 1988, p. 20; Holm and Lowe 1995, pp. 30-
31; Degenhardt et al. 1996, p. 318; Rossman et al. 1996, p. 176; 
Manjarrez 1998, p. 465). In situations where native prey species are 
rare or absent, this snake's diet may include nonnative species, 
including larval and juvenile bullfrogs (Lithobates catesbeianus), 
mosquitofish (Gambusia affinis) (Holycross et al. 2006, p. 23; Emmons 
and Nowak 2013, p. 5), or other soft-rayed fish species. Chinese 
mystery snails (Cipangopaludina chinensis) have been reported as a prey 
item for northern Mexican gartersnakes at the Page Springs and Bubbling 
Ponds State Fish

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Hatcheries in Arizona, but some predation attempts on snails have 
proven fatal for gartersnakes because of their lower jaw becoming 
permanently lodged in the snails' shell (Young and Boyarski 2012, p. 
498). Venegas-Barrera and Manjarrez (2001, p. 187) reported the first 
observation of a snake in the natural diet of any species of Thamnophis 
after documenting the consumption by a Mexican gartersnake (subspecies 
not provided) of a Mexican alpine blotched gartersnake (Thamnophis 
scalaris).
    Marc[iacute]as-Garc[iacute]a and Drummond (1988, pp. 129-134) 
sampled the stomach contents of Mexican gartersnakes and the prey 
populations at (ephemeral) Lake Tecocomulco, Hidalgo, Mexico. Field 
observations indicated, with high statistical significance, that larger 
Mexican gartersnakes fed primarily upon aquatic vertebrates (fishes, 
frogs, and larval salamanders) and leeches, whereas smaller Mexican 
gartersnakes fed primarily upon earthworms and leeches (Marc[iacute]as-
Garc[iacute]a and Drummond 1988, p. 131). Marc[iacute]as-Garc[iacute]a 
and Drummond (1988, p. 130) also found that the birth of newborn T. 
eques tended to coincide with the annual peak density of annelids 
(earthworms and leeches). There is also preliminary evidence that birth 
may coincide with a pronounced influx of available prey in a given 
area, especially with that of explosive breeders, such as toads, but 
more research is needed to confirm such a relationship (Boyarski 2012, 
pers. comm.). Positive correlations were also made with respect to 
capture rates (which are correlated with population size) of T. eques 
to lake levels and to prey scarcity; that is, when lake levels were low 
and prey species scarce, Mexican gartersnake capture rates declined 
(Marc[iacute]as-Garc[iacute]a and Drummond 1988, p. 132). This 
indicates the importance of available water and an adequate prey base 
to maintaining viable populations of Mexican gartersnakes. 
Marc[iacute]as-Garc[iacute]a and Drummond (1988, p. 133) found that 
while certain prey items were positively associated with size classes 
of snakes, the largest of specimens consume any prey available.
    Native predators of the northern Mexican gartersnake include birds 
of prey, other snakes (kingsnakes (Lampropeltis sp.), whipsnakes 
(Coluber sp.), regal ring-necked snakes (Diadophis punctatus regalis), 
etc.), wading birds, mergansers (Mergus merganser), belted kingfishers 
(Megaceryle alcyon), raccoons (Procyon lotor), skunks (Mephitis sp.), 
and coyotes (Canis latrans) (Rosen and Schwalbe 1988, pp. 18, 39; 
Brennan et al. 2009, p. 123). Historically, large, highly predatory 
native fish species such as Colorado pikeminnow may have preyed upon 
northern Mexican gartersnake where the subspecies co-occurred. Native 
chubs (Gila sp.) may also prey on neonatal gartersnakes.
    Parasites have been observed in northern Mexican gartersnakes. 
Boyarski (2008b, pp. 5-6) recorded several snakes within the population 
at the Page Springs and Bubbling Ponds fish hatcheries with interior 
bumps or bulges along the anterior one-third of the body. The cause of 
these bumps was not identified or speculated upon, nor were there any 
signs of trauma to the body of these snakes in the affected areas. Dr. 
Jim Jarchow, a veterinarian with herpetological expertise, reviewed 
photographs of affected specimens and suggested the bumps may likely 
contain plerocercoid larvae of a pseudophyllidean tapeworm (possibly 
Spirometra spp.), which are common in fish- and frog-eating 
gartersnakes. This may not be detrimental to their health, provided the 
bumps do not grow large enough to impair movement or other bodily 
functions (Boyarski 2008b, p. 8). However, G[uacute]zman (2008, p. 102) 
documented the first observation of mortality of a Mexican gartersnake 
from a larval Eustrongylides sp. (endoparasitic nematode) which 
``raises the possibility that infection of Mexican gartersnakes by 
Eustrongylides sp. larvae might cause mortality in some wild 
populations,'' especially if those populations are under stress as a 
result of the presence of other threats.
    Sexual maturity in northern Mexican gartersnakes occurs at 2 years 
of age in males and at 2 to 3 years of age in females (Rosen and 
Schwalbe 1988, pp. 16-17). Northern Mexican gartersnakes are viviparous 
(bringing forth living young rather than eggs). Mating has been 
documented in April and May followed by the live birth of between 7 and 
38 newborns (average is 13.6) in July and August (Rosen and Schwalbe 
1988, p. 16; Nowak and Boyarski 2012, pp. 351-352). However, field 
observations in Arizona provide preliminary evidence that mating may 
also occur during the fall, but further research is required to confirm 
this hypothesis (Boyarski 2012, pers. comm.). Unlike other gartersnake 
species, which typically breed annually, one study suggests that only 
half of the sexually mature females within a population of northern 
Mexican gartersnake might reproduce in any one season (Rosen and 
Schwalbe 1988, p. 17).
Historical Distribution
    Within the United States, the northern Mexican gartersnake 
historically occurred predominantly in Arizona at elevations ranging 
from 130 to 6,150 ft (40 to 1,875 m). It was generally found where 
water was relatively permanent and supported suitable habitat. The 
northern Mexican gartersnake historically occurred in every county and 
nearly every subbasin within Arizona, from several perennial or 
intermittent creeks, streams, and rivers as well as lentic (still, non-
flowing water) wetlands such as cienegas, ponds, or stock tanks. 
Northern Mexican gartersnake records exist within the following 
subbasins in Arizona: Colorado River, Bill Williams River, Agua Fria 
River, Salt River, Tonto Creek, Verde River, Santa Cruz River, Cienega 
Creek, San Pedro River, Babocomari River, and the Rio San Bernardino 
(Black Draw) (Woodin 1950, p. 40; Nickerson and Mays 1970, p. 503; 
Bradley 1986, p. 67; Rosen and Schwalbe 1988, Appendix I; 1995, p. 452; 
1997, pp. 16-17; Holm and Lowe 1995, pp. 27-35; Sredl et al. 1995b, p. 
2; 2000, p. 9; Rosen et al. 2001, Appendix I; Holycross et al. 2006, 
pp. 1-2, 15-51; Brennan and Holycross 2006, p. 123; Radke 2006, pers. 
comm.; Rosen 2006, pers. comm.; Holycross 2006, pers. comm.; Cotton et 
al. 2013, p. 111). Numerous records for the northern Mexican 
gartersnake (through 1996) in Arizona are maintained in the Arizona 
Game and Fish Department's (AGFD) Heritage Database (1996a).
    Historically, the northern Mexican gartersnake had a limited 
distribution in New Mexico that consisted of scattered locations 
throughout the Upper Gila River watershed in Grant and western Hidalgo 
Counties, including the Upper Gila River, Mule Creek in the San 
Francisco River subbasin, and the Mimbres River (Price 1980, p. 39; 
Fitzgerald 1986, Table 2; Degenhardt et al. 1996, p. 317; Holycross et 
al. 2006, pp. 1-2).
    One record for the northern Mexican gartersnake exists for the 
State of Nevada, opposite Fort Mohave, in Clark County along the shore 
of the Colorado River that was dated 1911 (De Queiroz and Smith 1996, 
p. 155). The subspecies may have occurred historically in the lower 
Colorado River region of California, although we were unable to verify 
any museum records for California. Any populations of northern Mexican 
gartersnakes that may have historically occurred in either Nevada or 
California were likely associated directly with the Colorado River, and

[[Page 41504]]

we believe them to be currently extirpated.
    Within Mexico, northern Mexican gartersnakes historically occurred 
within the Sierra Madre Occidental and the Mexican Plateau in the 
Mexican states of Sonora, Chihuahua, Durango, Coahuila, Zacatecas, 
Guanajuato, Nayarit, Hidalgo, Jalisco, San Luis Potos[iacute], 
Aguascalientes, Tlaxacala, Puebla, M[eacute]xico, Veracruz, and 
Quer[eacute]taro, comprising approximately 85 percent of the total 
rangewide distribution of the subspecies (Conant 1963, p. 473; 1974, 
pp. 469-470; Van Devender and Lowe 1977, p. 47; McCranie and Wilson 
1987, p. 15; Rossman et al. 1996, p. 173; Lemos-Espinal et al. 2004, p. 
83). We are not aware of any systematic, rangewide survey effort for 
the northern Mexican gartersnake in Mexico and have not found survey 
data for the subspecies in Mexico to be published in the scientific 
literature or otherwise readily available, outside of the information 
already obtained. Therefore, we use other, tightly correlated 
ecological surrogates (such as native freshwater fish) to inform 
discussion on the status of aquatic communities and aquatic habitat in 
Mexico, and therefore on the likely status of northern Mexican 
gartersnake populations. This discussion is found below in the 
subheadings pertinent to Mexico.
Current Distribution and Population Status
    Where northern Mexican gartersnakes are locally abundant, they are 
usually reliably detected with significantly less effort than 
populations characterized as having low densities. Northern Mexican 
gartersnakes are well-camouflaged, secretive, and very difficult to 
detect in structurally complex, dense habitat where they could occur at 
very low population densities, which characterizes most occupied sites. 
Water clarity can also affect survey accuracy. We considered factors 
such as the date of the last known records for northern Mexican 
gartersnakes in an area, as well as records of one or more native prey 
species in making a conclusion on occupancy of the subspecies. We used 
the year 1980 to qualify occupancy because the 1980s marked the first 
systematic survey efforts for northern Mexican gartersnakes across 
their range (see Rosen and Schwalbe (1988, entire) and Fitzgerald 
(1986, entire)) and the last, previous records were often dated several 
decades prior and may not accurately represent the likelihood for 
current occupation. Several areas where northern Mexican gartersnakes 
were known to occur have received no, or very little, survey effort in 
the past several decades. Variability in survey design and effort makes 
it difficult to compare population sizes or trends among sites and 
between sampling periods. For each of the sites discussed in Appendix A 
(available at http://www.regulations.gov under Docket No. FWS-R2-ES-
2013-0071), we have attempted to translate and quantify search and 
capture efforts into comparable units (i.e., person-search hours and 
trap-hours) and have conservatively interpreted those results. Because 
the presence of suitable prey species in an area may provide evidence 
that the northern Mexican gartersnake may still persist in low density 
where survey data are sparse, a record of a native prey species was 
considered in our determination of occupancy of this subspecies.
    Data on population status of northern Mexican gartersnakes in the 
United States are largely summarized in gray literature provided 
through agency reports and related documents. In our literature review 
efforts that resulted in our 2006 and 2008 12-month findings (71 FR 
56227 and 73 FR 71788, respectively), we found that the status of the 
northern Mexican gartersnake has declined significantly in the last 30 
years. We found that, in as much as 90 percent of the northern Mexican 
gartersnakes' historical distribution in the United States, the 
subspecies occurs at low to very low population densities or may even 
be extirpated. The decline of the northern Mexican gartersnake is 
primarily the result of predation by and competition with harmful 
nonnative species, such as spiny-rayed fish, bullfrogs, and crayfish, 
that have been intentionally released, accidentally released, or 
dispersed through natural mechanisms. Regardless of how they got into 
the wild, harmful nonnative species are now virtually ubiquitous 
throughout the range of the northern Mexican gartersnake. Land uses 
that result in the dewatering of habitat, combined with increasing 
drought, have destroyed significant amounts of habitat throughout the 
northern Mexican gartersnake's range and have also contributed to 
population declines.
    Holycross et al. (2006, p. 66) detected the northern Mexican 
gartersnake at only 2 of 11 historical localities along the northern-
most part of its range from which the subspecies was previously known. 
The only viable northern Mexican gartersnake populations in the United 
States where the subspecies remains reliably detected are all located 
in Arizona: (1) The Page Springs and Bubbling Ponds State Fish 
Hatcheries along Oak Creek, (2) lower Tonto Creek, (3) the upper Santa 
Cruz River in the San Rafael Valley, (4) the Bill Williams River, and 
(5) the upper Verde River. In New Mexico, the northern Mexican 
gartersnake may occur in extremely low population densities within its 
historical distribution; limited survey effort is inconclusive to 
determine extirpation. The status of the northern Mexican gartersnake 
on tribal lands, such as those owned by the White Mountain or San 
Carlos Apache Tribes, is poorly known due to historically limited 
survey access. As stated previously, less is known specifically about 
the current distribution of the northern Mexican gartersnake in Mexico 
due to limited access to information on survey efforts and field data 
from Mexico.
    In Table 1 below, we summarize the population status of northern 
Mexican gartersnakes at all known localities throughout their United 
States distribution, as supported by museum records or reliable 
observations. For a detailed discussion that explains the rationale for 
site-by-site conclusions on occupancy, please see Appendix A (available 
at http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071). 
General rationale is provided in the introductory paragraph to this 
section, ``Current Distribution and Population Status.''

        Table 1--Current Population Status of the Northern Mexican Gartersnake in the United States. References Cited Are Provided in Appendix A
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Suitable physical     Native prey  species    Harmful nonnative
           Location                   Last record          habitat present            present            species present          Population status
--------------------------------------------------------------------------------------------------------------------------------------------------------
Gila River (NM, AZ)...........  2002..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Spring Canyon (NM)............  1937..................  Yes..................  Possible.............  Likely...............  Likely extirpated.
Mule Creek (NM)...............  1983..................  Yes..................  Yes..................  Yes..................  Likely not viable.

[[Page 41505]]

 
Mimbres River (NM)............  Likely early 1900s....  Yes..................  Yes..................  Yes..................  Likely extirpated.
Lower Colorado River (AZ).....  1904..................  Yes..................  Yes..................  Yes..................  Likely extirpated.
Bill Williams River (AZ)......  2012..................  Yes..................  Yes..................  Yes..................  Likely viable.
Agua Fria River (AZ)..........  1986..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Little Ash Creek (AZ).........  1984..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Lower Salt River (AZ).........  1964..................  Yes..................  Yes..................  Yes..................  Likely extirpated.
Black River (AZ)..............  1982..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Big Bonito Creek (AZ).........  1986..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Tonto Creek (AZ)..............  2005..................  Yes..................  Yes..................  Yes..................  Likely viable.
Upper Verde River (AZ)........  2012..................  Yes..................  Yes..................  Yes..................  Likely viable.
Oak Creek (AZ) (Page Springs    2012..................  Yes..................  Yes..................  Yes..................  Likely viable.
 and Bubbling Ponds State Fish
 Hatcheries).
Spring Creek (AZ).............  1986..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Sycamore Creek (AZ)...........  1954..................  Yes..................  Possible.............  Yes..................  Likely extirpated.
Upper Santa Cruz River/San      2012..................  Yes..................  Yes..................  Yes..................  Likely viable.
 Rafael Valley (AZ).
Redrock Canyon (AZ)...........  2008..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Sonoita Creek (AZ)............  1974..................  Yes..................  Possible.............  Yes..................  Likely extirpated.
Scotia Canyon (AZ)............  2009..................  Yes..................  Yes..................  No...................  Likely not viable.
Parker Canyon (AZ)............  1986..................  Yes..................  Possible.............  Yes..................  Likely not viable.
Las Cienegas National           2012..................  Yes..................  Yes..................  Possible.............  Likely not viable.
 Conservation Area and Cienega
 Creek Natural Preserve (AZ).
Lower Santa Cruz River (AZ)...  1956..................  Yes..................  Yes..................  Yes..................  Likely extirpated.
Buenos Aires National Wildlife  2000..................  Yes..................  Yes..................  Yes..................  Likely not viable.
 Refuge (AZ).
Bear Creek (AZ)...............  1987..................  Yes..................  Yes..................  Yes..................  Likely not viable.
San Pedro River (AZ)..........  1996..................  Yes..................  Yes..................  Yes..................  Likely not viable.
Babocomari River and Cienega    1986..................  Yes..................  Possible.............  Yes..................  Likely not viable.
 (AZ).
Canelo Hills-Sonoita            2012..................  Yes..................  Yes..................  Yes..................  Likely not viable.
 Grasslands Area (AZ).
San Bernardino National         1997..................  Yes..................  Yes..................  Yes..................  Likely not viable.
 Wildlife Refuge (AZ).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes: ``Possible'' means there were no conclusive data found. ``Likely extirpated'' means the last record for an area pre-dated 1980 and existing
  threats suggest the species is likely extirpated. ``Likely not viable'' means the last record for an area pre-dated 1980 and existing threats suggest
  the species is likely extirpated. ``Likely viable'' means that the species is reliably found with minimal to moderate survey effort and the population
  is generally considered viable.

    Table 1 lists the 29 known localities for the northern Mexican 
gartersnake in the United States. Appendix A (available at http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071) discusses 
such considerations as the physical condition of habitat, the 
composition of the aquatic biological community, the existence of 
significant threats, and the length of time since the last known 
observation of the subspecies in presenting rationale for determining 
occupancy status at each locality. We have concluded that in as many as 
24 of 29 known localities in the United States (83 percent), the 
northern Mexican gartersnake population is likely not viable and may 
exist at low population densities that could be threatened with 
extirpation or may already be extirpated. In most localities where the 
species may occur at low population densities, existing survey data are 
insufficient to prove extirpation. Only five populations of northern 
Mexican gartersnakes in the United States are considered likely viable 
where the species remains reliably detected. When considering the total 
number of stream miles in the United States that historically supported 
the northern Mexican gartersnake that are now permanently dewatered 
(except in the case of temporary flows in response to heavy 
precipitation), we concluded that as much as 90 percent of historical 
populations in the United States either occur at low densities or are 
extirpated. As displayed in Table 1, harmful nonnative species are a 
concern in almost every northern Mexican gartersnake locality in the 
United States and the most significant reason for their decline, as 
discussed in depth in our threats analysis below.
    Listed as threatened throughout its range in Mexico by the Mexican 
Government, our understanding of the northern Mexican gartersnake's 
specific population status throughout its range in Mexico is less 
precise than that known for its United States distribution because 
survey efforts are less, and sufficient, available records do not exist 
or are difficult to obtain. However, we have assembled and reviewed an 
extensive body of scientific information on known, regional threats to 
northern Mexican gartersnakes and to their primary prey species. This 
information is presented in greater detail below in our specific 
discussion of threats to the species in Mexico.

Narrow-Headed Gartersnake

Species Description
    The narrow-headed gartersnake is a small to medium-sized 
gartersnake with a maximum total length of 44 in (112 cm mm) (Painter 
and Hibbitts 1996, p. 147). Its eyes are set high on its unusually 
elongated head, which narrows to the snout, and it lacks striping on 
the dorsum (top) and sides, which distinguishes its appearance from 
other gartersnake species with which it could co-occur (Rosen and 
Schwalbe 1988, p. 7). The base color is usually tan or grey-brown (but 
may darken) with conspicuous brown, black, or reddish spots that become 
indistinct towards the

[[Page 41506]]

tail (Rosen and Schwalbe 1988, p. 7; Boundy 1994, p. 126). The scales 
are keeled. Degenhardt et al. (1996, p. 327), Rossman et al. (1996, pp. 
242-244), and Ernst and Ernst (2003, p. 416) further describe the 
species.
Taxonomy
    The narrow-headed gartersnake is a member of the family Colubridae 
and subfamily Natricinae (harmless live-bearing snakes) (Lawson et al. 
2005, p. 596). The taxonomy of the genus Thamnophis has a complex 
history partly because many of the species are similar in appearance 
and scutelation (arrangement of scales), but also because many of the 
early museum specimens were in such poor and faded condition that it 
was difficult to study them (Conant 2003, p. 6). The narrow-headed 
gartersnake has a particularly complex taxonomic history due to its 
morphology and feeding habits. There are approximately 30 species 
described in the gartersnake genus Thamnophis (Rossman et al. 1996, pp. 
xvii-xviii). Two large overlapping clades (related taxonomic groups) of 
gartersnakes have been identified called the ``Mexican'' and 
``widespread'' clades, supported by allozyme and mitochondrial DNA 
genetic analyses (de Queiroz et al. 2002, p. 321). Thamnophis 
rufipunctatus is a member of the ``Mexican'' clade and is most closely 
related taxonomically to the southern Durango spotted gartersnake 
(Thamnophis nigronuchalis) (de Queiroz and Lawson 1994, p. 217; de 
Queiroz et al. 2002; p. 321).
    Due to the narrow-headed gartersnake's morphology and feeding 
habits, there has been considerable deliberation among taxonomists 
about the correct association of this species within seven various 
genera over time (Rosen and Schwalbe 1988, pp. 5-6); chiefly, between 
the genera Thamnophis (the ``gartersnakes'') and Nerodia (the 
``watersnakes'') (Pierce 2007, p. 5). Chaisson and Lowe (1989, pp. 110-
118) argued that the pattern of ultrastructural (as revealed by an 
electron microscope) pores in the scales of narrow-headed gartersnakes 
provided evidence that the species is more appropriately placed within 
the genus Nerodia. However, De Queiroz and Lawson (1994, p. 217) 
rejected this premise using mitochondrial DNA (mtDNA) genetic analyses 
to refute the inclusion of the narrow-headed gartersnake in the genus 
Nerodia and maintain the species within the genus Thamnophis.
    The narrow-headed gartersnake was first described as Chilopoma 
rufipunctatum by E. D. Cope (in Yarrow, 1875). Recently, Thamnophis 
rufipunctatus nigronuchalis and T. r. unilabialis were recognized as 
subspecies under T. rufipunctatus and comprised what was considered the 
T. rufipunctatus complex. However, Rossman et al. (1996, pp. 244-246) 
elevated T. r. nigronuchalis to full species designation and argued 
recognition of T. r. unilabialis be discontinued due to the diagnostic 
differences being too difficult to discern. Wood et al. (2011, p. 14) 
used genetic analysis of the T. rufipunctatus complex to propose the 
elevation of these three formerly recognized subspecies as three 
distinct species, as a result of a combination of interglacial warming, 
ecological and life-history constraints, and genetic drift, which 
promoted differentiation of these three species throughout the warming 
and cooling periods of the Pleistocene epoch (Wood et al. 2011, p. 15). 
We use these most recent and complete data in acknowledging these three 
entities as unique species: T. rufipunctatus (along the Mogollon Rim of 
Arizona and New Mexico), T. unilabialis (Chihuahua, eastern Sonora, and 
northern Durango, Mexico), and T. nigronuchalis (southern Durango, 
Mexico).
    Several common names have been used for this species including the 
red-spotted gartersnake, the brown-spotted gartersnake, and the 
currently used, narrow-headed gartersnake (Rosen and Schwalbe 1988, p. 
5). Further discussion of the taxonomic history of the narrow-headed 
gartersnake is available in Crother (2012, p. 71), Degenhardt et al. 
(1996, p. 326); Rossman et al. (1996, p. 244), De Queiroz and Lawson 
(1994, pp. 213-229); Rosen and Schwalbe (1988, pp. 5-7); and De Queiroz 
et al. (2002, p. 321).
Habitat and Natural History
    The narrow-headed gartersnake is widely considered to be one of the 
most aquatic of the gartersnakes (Drummond and Marcias Garcia 1983, pp. 
24, 27; Rossman et al. 1996, p. 246). This species is strongly 
associated with clear, rocky streams, using predominantly pool and 
riffle habitat that includes cobbles and boulders (Rosen and Schwalbe 
1988, pp. 33-34; Degenhardt et al. 1996, p. 327; Rossman et al. 1996, 
p. 246; Ernst and Ernst 2003, p. 417). Rossman et al. (1996, p. 246) 
also note the species has been observed using lake shoreline habitat in 
New Mexico. Narrow-headed gartersnakes occur at elevations from 
approximately 2,300 to 8,200 ft (700 to 2,500 m), inhabiting Petran 
Montane Conifer Forest, Great Basin Conifer Woodland, Interior 
Chaparral, and the Arizona Upland subdivision of Sonoran Desertscrub 
communities (Rosen and Schwalbe 1988, p. 33; Brennan and Holycross 
2006, p. 122). An extensive evaluation of habitat use of narrow-headed 
gartersnakes along Oak Creek in Arizona is provided in Nowak and 
Santana-Bendix (2002, pp. 26-37). Rosen and Schwalbe (1988, p. 35) 
found narrow-headed gartersnake densities may be highest at the 
conjunction of cascading riffles with pools, where waters were deeper 
than 20 in (0.5 m) in the riffle and deeper than 40 in (1 m) in the 
immediately adjoining area of the pool, but more than twice the number 
of snakes were found in pools rather than riffles.
    Where narrow-headed gartersnakes are typically found in the water, 
little aquatic vegetation exists (Rosen and Schwalbe 1988, p. 34). 
However, bank-line vegetation is an important component to suitable 
habitat for this species. Narrow-headed gartersnakes will usually bask 
in situations where a quick escape can be made, whether that is into 
the water or under substrate such as rocks (Fleharty 1967, p. 16). 
Common plant species associations include Arizona alder (Alnus 
oblongifolia) (highest correlation with occurrence of the narrow-headed 
gartersnake), velvet ash (Fraxinus pennsylvanica), willows (Salix 
ssp.), canyon grape (Vitis arizonica), blackberry (Rubus ssp.), Arizona 
sycamore (Platanus wrightii), Arizona black walnut (Juglans major), 
Freemont cottonwood (Populus fremontii), Gambel oak (Quercus gambelii), 
and ponderosa pine (Pinus ponderosa) (Rosen and Schwalbe 1988, pp. 34-
35). Rosen and Schwalbe (1988, p. 35) noted that the composition of 
bank-side plant species and canopy structure were less important to the 
species' needs than was the size class of the plant species present; 
narrow-headed gartersnakes prefer to use shrub- and sapling-sized 
plants for thermoregulating (basking) at the waters' edge (Degenhardt 
et al. 1996, p. 327).
    Narrow-headed gartersnakes may opportunistically forage within 
dammed reservoirs formed by streams that are occupied habitat, such as 
at Wall Lake (located at the confluence of Taylor Creek, Hoyt Creek, 
and the East Fork Gila River) (Fleharty 1967, p. 207) and most recently 
at Snow Lake in 2012 (located near the confluence of Snow Creek and the 
Middle Fork Gila River) (Hellekson 2012b, pers. comm.) in New Mexico, 
but records from impoundments are rare in the literature. The species 
evolved in the absence of such habitat, and impoundments are generally 
managed as sport fisheries (Wall Lake and Snow Lake are) and

[[Page 41507]]

often maintain populations of harmful nonnative species that are 
incompatible with narrow-headed gartersnakes.
    The narrow-headed gartersnake is surface-active generally between 
March and November (Nowak 2006, p. 16). Little information on suitable 
temperatures for surface activity of the narrow-headed gartersnake 
exists; however, it is presumed to be rather cold-tolerant based on its 
natural history and foraging behavior that often involves clear, cold 
streams at higher elevations. Along Oak Creek in Arizona, Nowak (2006, 
Appendix 1) found the species to be active in air temperatures ranging 
from 52 to 89[emsp14][deg]F (11 to 32 [deg]C) and water temperatures 
ranging from 54 to 72[emsp14][deg]F (12 to 22 [deg]C). Jennings and 
Christman (2011, pp. 12-14) found body temperatures of narrow-headed 
gartersnakes along the Tularosa River averaged approximately 
68[emsp14][deg]F (20 [deg]C) during the mid-morning hours and 
81[emsp14][deg]F (27 [deg]C) in the late afternoon during the period 
from late July and August. Variables that affect their body temperature 
include the temperature of the microhabitat used and water temperature 
(most predictive), but slope aspect and the surface area of cover used 
also influenced body temperatures (Jennings and Christman 2011, p. 13). 
Narrow-headed gartersnakes have a lower preferred temperature for 
activity as compared to other species of gartersnakes (Fleharty 1967, 
p. 228), which may facilitate their highly aquatic nature in cold 
streams.
    Narrow-headed gartersnakes specialize on fish as their primary prey 
item (Rosen and Schwalbe 1988, p. 38; Degenhardt et al. 1996, p. 328; 
Rossman et al. 1996, p. 247; Nowak and Santana-Bendix 2002, pp. 24-25; 
Nowak 2006, p. 22) and are believed to be mainly visual hunters 
(Hibbitts and Fitzgerald 2005, p. 364), heavily dependent on visual 
cues when foraging based on comparative analyses among other species of 
gartersnakes (de Queiroz 2003, p. 381). Unlike many other species of 
gartersnakes that are active predators (actively crawl about in search 
of prey), narrow-headed gartersnakes are considered to be ambush 
predators (sit-and-wait method) (Brennan and Holycross 2006, p. 122; 
Pierce et al. 2007, p. 8). The specific gravity (ratio of the mass of a 
solid object to the mass of the same volume of water) of the narrow-
headed gartersnake was found to be nearly 1, which means that the snake 
can maintain its desired position in the water column with ease, an 
adaptation to facilitate foraging on the bottom of streams (Fleharty 
1967, pp. 218-219). Native fish species most often associated as prey 
items for the narrow-headed gartersnake include Sonora sucker 
(Catostomus insignis), desert sucker (C. clarki), speckled dace 
(Rhinichthys osculus), roundtail chub (Gila robusta), Gila chub (Gila 
intermedia), and headwater chub (Gila nigra) (Rosen and Schwalbe 1988, 
p. 39; Degenhardt et al. 1996, p. 328). Nonnative species used as prey 
by narrow-headed gartersnakes are most often salmonid species (trout); 
most commonly brown (Salmo trutta) and rainbow trout (Oncorhynchus 
mykiss), as these species are commonly stocked in, or near, occupied 
narrow-headed gartersnake habitat (Rosen and Schwalbe 1988, p. 39; 
Nowak 2006, pp. 22-23). Fleharty (1967, p. 223) reported narrow-headed 
gartersnakes eating green sunfish, but green sunfish is not considered 
a suitable prey item.
    Several reviews (Stebbins 1985, p. 199; Deganhardt et al. 1996, p. 
328; Ernst and Ernst 2003, p. 418) state that the narrow-headed 
gartersnake will also prey upon frogs, tadpoles, and salamanders. 
Fitzgerald (1986, p. 6) referenced the Stebbins (1985) account as the 
only substantiated account of the species accepting something other 
than fish as prey, apparently as the result of finding a small 
salamander larvae in the stomach of an individual in Durango, Mexico. 
Formerly recognized as a subspecies of Thamnophis rufipunctatus, that 
individual is now recognized as T. unilabialis (Wood et al. 2011, p. 
3). We found an account of narrow-headed gartersnakes consuming red-
spotted toads in captivity (Woodin 1950, p. 40). Despite several 
studies focusing on the ecology of narrow-headed gartersnakes in recent 
times, there are no other records of narrow-headed gartersnakes, under 
current taxonomic recognition, feeding on prey items other than fish. 
We, along with species experts, do not consider amphibians as 
ecologically important prey for this species based on our review of the 
literature.
    Native predators of the narrow-headed gartersnake include birds of 
prey, other snakes such as kingsnakes, whipsnakes, or regal ring-necked 
snakes, wading birds, mergansers, belted kingfishers, raccoons, skunks, 
and coyotes (Rosen and Schwalbe 1988, pp. 18, 39; Brennan et al. 2009, 
p. 123). Historically, large, highly predatory native fish species such 
as Colorado pikeminnow may have preyed upon narrow-headed gartersnakes 
where the species co-occurred. Native chubs (Gila sp.) may also prey on 
neonatal gartersnakes.
    Sexual maturity in narrow-headed gartersnakes occurs at 2.5 years 
of age in males and at 2 years of age in females (Deganhardt et al. 
1996, p. 328). Narrow-headed gartersnakes are viviparous. The 
reproductive cycle for narrow-headed gartersnakes appears to be longer 
than other gartersnake species; females begin the development of 
follicles in early March, and gestation takes longer (Rosen and 
Schwalbe 1988, pp. 36-37). Female narrow-headed gartersnakes breed 
annually and give birth to 4 to 17 offspring from late July into early 
August, perhaps earlier at lower elevations (Rosen and Schwalbe 1988, 
pp. 35-37). Sex ratios in narrow-headed gartersnake populations can be 
skewed in favor of females (Fleharty 1967, p. 212).
Historical Distribution
    The historical distribution of the narrow-headed gartersnake ranged 
across the Mogollon Rim and along its associated perennial drainages 
from central and eastern Arizona, southeast to southwestern New Mexico 
at elevations ranging from 2,300 to 8,000 ft (700 to 2,430 m) (Rosen 
and Schwalbe 1988, p. 34; Rossman et al. 1996, p. 242; Holycross et al. 
2006, p. 3). The species was historically distributed in headwater 
streams of the Gila River subbasin that drain the Mogollon Rim and 
White Mountains in Arizona, and the Gila Wilderness in New Mexico; 
major subbasins in its historical distribution included the Salt and 
Verde River subbasins in Arizona, and the San Francisco and Gila River 
subbasins in New Mexico (Holycross et al. 2006, p. 3). Holycross et al. 
(2006, p. 3) suspect the species was likely not historically present in 
the lowest reaches of the Salt, Verde, and Gila rivers, even where 
perennial flow persists. Numerous records for the narrow-headed 
gartersnake (through 1996) in Arizona are maintained in the AGFD's 
Heritage Database (1996b). The narrow-headed gartersnake as currently 
recognized does not occur in Mexico.
Current Distribution and Population Status
    Where narrow-headed gartersnakes are locally abundant, they can 
usually be detected reliably and with significantly less effort than 
populations characterized as having low densities. Narrow-headed 
gartersnakes are well-camouflaged, secretive, and very difficult to 
detect in structurally complex, dense habitat where they could occur at 
very low population densities, which characterizes most occupied sites. 
Water clarity can also affect survey accuracy. We considered factors 
such as the date of the last known records for narrow-headed 
gartersnakes in an area, as well as

[[Page 41508]]

records of one or more native prey species in making a conclusion on 
species occupancy. We used all records that were dated 1980 or later 
because the 1980s marked the first systematic survey efforts for 
narrow-headed gartersnakes species across their range (see Rosen and 
Schwalbe (1988, entire) and Fitzgerald (1986, entire)), and the last, 
previous records were often dated several decades prior and may not 
accurately represent the likelihood for current occupation. Several 
areas where narrow-headed gartersnakes were known to occur have 
received no, or very little, survey effort in the past several decades. 
Variability in survey design and effort makes it difficult to compare 
population sizes or trends among sites and between sampling periods. 
Thus, for each of the sites discussed in Appendix A (available at 
http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071), we 
have attempted to translate and quantify search and capture efforts 
into comparable units (i.e., person-search hours and trap-hours) and 
have conservatively interpreted those results. Because the presence of 
suitable prey species in an area may provide evidence that northern 
Mexican gartersnake may still persist in low density where survey data 
are sparse, a record of a native prey species was considered in our 
determination of occupancy of this species.
    Population status information, based on our review of the best 
scientific and commercial data available, suggests that the narrow-
headed gartersnake has experienced significant declines in population 
density and distribution along streams and rivers where it was formerly 
well-documented and reliably detected. Many areas where the species may 
occur likely rely on emigration of individuals from occupied habitat 
into those areas to maintain the species, provided there are no 
barriers to movement. Holycross et al. (2006) represents the most 
recent, comprehensive survey effort for narrow-headed gartersnakes in 
Arizona. Our most current information on the species' status in New 
Mexico comes from a species expert who is completing a graduate degree 
focused on the relationship between narrow-headed gartersnake 
populations and fish communities in the upper Gila and San Francisco 
river drainages (Helleckson 2012a, pers. comm.). Narrow-headed 
gartersnakes were detected in only 5 of 16 historical localities in 
Arizona and New Mexico surveyed by Holycross et al. (2006) in 2004 and 
2005. Population densities have noticeably declined in many 
populations, as compared to previous survey efforts (Holycross et al. 
2006, p. 66). Holycross et al. (2006, pp. 66-67) compared narrow-headed 
gartersnake detections based on results from their effort and that of 
previous efforts in the same locations and found that significantly 
more effort is required to detect this species in areas where it was 
formerly robust, such as along Eagle Creek (AZ), the East Verde River 
(AZ), the San Francisco River (NM), the Black River (AZ), and the Blue 
River (AZ).
    As of 2011, the only remaining narrow-headed gartersnake 
populations where the species could reliably be found were located at: 
(1) Whitewater Creek (New Mexico), (2) Tularosa River (New Mexico), (3) 
Diamond Creek (New Mexico), (4) Middle Fork Gila River (New Mexico), 
and (5) Oak Creek Canyon (Arizona). However, populations found in 
Whitewater Creek and the Middle Fork Gila River were likely 
significantly affected by New Mexico's largest wildfire in State 
history, the Whitewater-Baldy Complex Fire, which occurred in June 
2012. In addition, salvage efforts were initiated for these two 
populations, which included the removal of 25 individuals from 
Whitewater Creek and 14 individuals from the Middle Fork Gila River 
before the onset of summer rains in 2012. The status of those 
populations has likely deteriorated as a result of subsequent declines 
in resident fish communities due to heavy ash and sediment flows, 
resulting fish kills, and the removal of snakes, but subsequent survey 
data have not been collected. If the Whitewater Creek and Middle Fork 
Gila River populations did decline as a result of these factors, only 
three remaining populations of this species remain viable today across 
their entire distribution. Such unnaturally large wildfires have become 
increasingly common across the Mogollon Rim of Arizona and New Mexico 
where the narrow-headed gartersnake historically occurred. The status 
of the narrow-headed gartersnake on tribal land is poorly known, due to 
limited survey access.
    In Table 2 below, we summarize the population status of the narrow-
headed gartersnake at all known localities throughout its distribution, 
as supported by museum records or reliable observations. For a detailed 
discussion that explains the rationale for site-by-site conclusions on 
occupancy, please see Appendix A (available at http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071). General 
rationale is provided in the introductory paragraph to this section, 
``Current Distribution and Population Status.''

Table 2--Current Population Status of the Narrow-Headed Gartersnake. References Cited Are Provided in Appendix A
----------------------------------------------------------------------------------------------------------------
                                                Suitable                           Harmful
           Location            Last record  physical habitat    Native prey       nonnative        Population
                                                 present      species present  species present       status
----------------------------------------------------------------------------------------------------------------
West Fork Gila River (NM)....         2011  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Middle Fork Gila River (NM)..         2012  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
East Fork Gila River (NM)....         2006  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Gila River (AZ, NM)..........         2009  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Snow Creek/Snow Lake (NM)....         2012  Yes.............  No.............  Yes............  Likely not
                                                                                                 viable.
Gilita Creek (NM)............         2009  Yes.............  Yes............  No.............  Likely not
                                                                                                 viable.
Iron Creek (NM)..............         2009  Yes.............  Yes............  No.............  Likely not
                                                                                                 viable.
Little Creek (NM)............         2010  Yes.............  Possible.......  Yes............  Likely not
                                                                                                 viable.
Turkey Creek (NM)............         1985  Yes.............  Yes............  Possible.......  Likely not
                                                                                                 viable.
Beaver Creek (NM)............         1949  Yes.............  Possible.......  Yes............  Likely
                                                                                                 extirpated.
Black Canyon (NM)............         2010  Yes.............  Yes............  No.............  Likely not
                                                                                                 viable.
Taylor Creek (NM)............         1960  Yes.............  No.............  Yes............  Likely
                                                                                                 extirpated.
Diamond Creek (NM)...........         2011  Yes.............  Yes............  Yes............  Likely viable.
Tularosa River (NM)..........         2012  Yes.............  Yes............  Yes............  Likely viable.
Whitewater Creek (NM)........         2012  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
San Francisco River (NM).....         2011  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
South Fork Negrito Creek (NM)         2011  Yes.............  Possible.......  Yes............  Likely not
                                                                                                 viable.

[[Page 41509]]

 
Blue River (AZ)..............         2007  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Dry Blue Creek (AZ, NM)......         2010  Yes.............  Possible.......  Yes............  Likely not
                                                                                                 viable.
Campbell Blue Creek (AZ, NM).         2010  Yes.............  Possible.......  Yes............  Likely not
                                                                                                 viable.
Saliz Creek (NM).............         2012  Yes.............  Possible.......  Yes............  Likely not
                                                                                                 viable.
Eagle Creek (AZ).............         1991  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Black River (AZ).............         2009  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
White River (AZ).............         1986  Yes.............  Yes............  Possible.......  Likely not
                                                                                                 viable.
Diamond Creek (AZ)...........         1986  Yes.............  Possible.......  Possible.......  Likely not
                                                                                                 viable.
Tonto Creek (tributary to Big         1915  Yes.............  Possible.......  Possible.......  Likely
 Bonita Creek, AZ).                                                                              extirpated.
Canyon Creek (AZ)............         1991  Yes.............  Yes............  No.............  Likely not
                                                                                                 viable.
Upper Salt River (AZ)........         1985  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Cibeque Creek (AZ)...........         1991  Yes.............  Yes............  Possible.......  Likely not
                                                                                                 viable.
Carrizo Creek (AZ)...........         1997  Yes.............  Yes............  Possible.......  Unreliably
                                                                                                 detected.
Big Bonito Creek (AZ)........         1957  Yes.............  Yes............  Yes............  Likely
                                                                                                 extirpated.
Haigler Creek (AZ)...........  Early 1990s  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Houston Creek (AZ)...........         2005  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Tonto Creek (tributary to             2005  Yes.............  Yes............  Yes............  Likely not
 Salt River, AZ).                                                                                viable.
Deer Creek (AZ)..............         1995  No..............  No.............  No.............  Likely
                                                                                                 extirpated.
Upper Verde River (AZ).......         2012  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
Oak Creek (AZ)...............         2012  Yes.............  Yes............  Yes............  Likely viable.
East Verde River (AZ)........         1992  Yes.............  Yes............  Yes............  Likely not
                                                                                                 viable.
----------------------------------------------------------------------------------------------------------------
``Possible'' means there were no conclusive data found.

    ``Likely extirpated'' means the last record for an area pre-dated 
1980 and existing threats suggest the species is likely extirpated. 
``Likely not viable'' means there is a post-1980 record for the 
species, it is not reliably found with minimal to moderate survey 
effort, and threats exist which suggest the population may be low 
density or could be extirpated, but there is insufficient evidence to 
confirm extirpation. ``Likely viable'' means that the species is 
reliably found with minimal to moderate survey effort and the 
population is generally considered viable.
    Table 2 lists the 38 known localities for narrow-headed 
gartersnakes throughout their range. Appendix A (available at http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071) discusses 
such considerations as the physical condition of habitat, the 
composition of the aquatic biological community, the existence of 
significant threats, and the length of time since the last known 
observation of the species in presenting rationale for determining 
occupancy status at each locality. We have concluded that in as many as 
29 of 38 known localities (76 percent), the narrow-headed gartersnake 
population is likely not viable and may exist at low population 
densities that could be threatened with extirpation or may already be 
extirpated but survey data are lacking in areas where access is 
restricted. In most localities where the species may occur at low 
population densities, existing survey data are insufficient to conclude 
extirpation. As of 2012, narrow-headed gartersnake populations are 
considered likely viable in 3 localities (8 percent) where individuals 
are reliable detected. As displayed in Table 2, harmful nonnative 
species are a concern for almost every narrow-headed gartersnake 
population throughout their range. The ramifications of this are 
significant because of the effect these harmful nonnative species have 
on the resident native fish communities and the fact that this species 
is a specialized, fish-only predator. We discuss this and other 
important factors that have contributed to the decline of narrow-headed 
gartersnakes throughout their range in our threats analysis below.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1533), and its implementing 
regulations at 50 CFR part 424, set forth the procedures for adding 
species to the Federal Lists of Endangered and Threatened Wildlife and 
Plants. Under section 4(a)(1) of the Act, we may list a species based 
on any of the following five factors: (A) The present or threatened 
destruction, modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; and (E) other natural or manmade 
factors affecting its continued existence. Listing actions may be 
warranted based on any of the above threat factors, singly or in 
combination.
    In the following threats analysis, we treat both gartersnake 
species in a combined discussion because of partially overlapping 
ranges, similar natural histories, similar responses to threats, and 
the fact that many threats are shared in common throughout their 
ranges.

The Weakened Status of Native Aquatic Communities

    Riparian and aquatic communities in both the United States and 
Mexico have been significantly impacted by a shift in species' 
composition, from one of primarily native fauna, to one being 
increasingly dominated by an expanding assemblage of nonnative animal 
species. Many of these nonnative species have been intentionally or 
accidentally introduced, including crayfish, bullfrogs, and nonnative, 
spiny-rayed fish. Harmful nonnative species have been introduced or 
have spread into new areas through a variety of mechanisms, including 
intentional and accidental releases, sport stocking, aquaculture, 
aquarium releases, and bait-bucket release.
    The occurrence of harmful nonnative species, such as the bullfrog, 
the northern (virile) crayfish (Orconectes virilis), red swamp crayfish 
(Procambarus clarkii), and numerous species of nonnative, spiny-rayed 
fish,

[[Page 41510]]

has contributed to rangewide declines in both species of gartersnake, 
and continues to be the most significant threat to the northern Mexican 
and narrow-headed gartersnakes, and to their prey base, as a result of 
direct predation, competition, and modification of habitat as evidenced 
in a broad body of literature, the most recent of which extends from 
1985 to the present (Meffe 1985, pp. 179-185; Propst et al. 1986, pp. 
14-31, 82; 1988, p. 64; 2009, pp. 5-17; Minckley 1987, pp. 2, 16; 1993, 
pp. 7-13; Rosen and Schwalbe 1988, pp. 28, 32; 1997, p. 1; Bestgen and 
Propst 1989, pp. 409-410; Clarkson and Rorabaugh 1989, pp. 531, 535; 
Papoulias et al. 1989, pp. 77-80; Marsh and Minckley 1990, p. 265; 
Jakle 1992, pp. 3-5; 1995, pp. 5-7; ASU 1994, multiple reports; 1995, 
multiple reports; 2008, multiple reports; Stefferud and Stefferud 1994, 
p. 364; Douglas et al. 1994, pp. 9-19; Rosen et al. 1995, pp. 257-258; 
1996b, pp. 2, 11-13; 2001, p. 2; Springer 1995, pp. 6-10; Degenhardt et 
al. 1996, p. 319; Fernandez and Rosen 1996, pp. 8, 23-27, 71, 96; 
Richter et al. 1997, pp. 1089, 1092; Weedman and Young 1997, pp. 1, 
Appendices B, C; Inman et al. 1998, p. 17; Rinne et al. 1998, pp. 4-6; 
2004, pp. 1-2; Jahrke and Clark 1999, pp. 2-7; Minckley et al. 2002, 
pp. 696; Nowak and Santana-Bendix 2002, Table 3; Propst 2002, pp. 21-
25; DFT 2003, pp. 1-3, 5-6, 19; 2004, pp. 1-2, 4-5, 10, Table 1; 2006, 
pp. iii, 25; Marsh et al. 2003, p. 667; Bonar et al. 2004, pp. 13, 16-
21; Rinne 2004, pp. 1-2; Clarkson et al. 2005, p. 20; 2008, pp. 3-4; 
Fagan et al. 2005, pp. 34, 34-41; Knapp 2005, pp. 273-275; Olden and 
Poff 2005, pp. 82-87; AGFD 2006, p. 83; Turner 2007, p. 41; Holycross 
et al. 2006, pp. 13-15; Brennan and Holycross 2006, p. 123; Brennan 
2007, pp. 5, 7; Turner and List 2007, p. 13; USFWS 2007, pp. 22-23; 
Burger 2008, p. 4; Caldwell 2008a, 2008b; Duifhuis Rivera et al. 2008, 
p. 479, Jones 2008b; d'Orgeix 2008; Haney et al. 2008, p. 59; Luja and 
Rodr[iacute]guez-Estrella 2008, pp. 17-22; Probst et al. 2008, pp. 
1242-1243; Rorabaugh 2008a, p. 25; USFS 2008; Wallace et al. 2008, pp. 
243-244; Witte et al. 2008, p. 1; Bahm and Robinson 2009a, pp. 2-6; 
2009b, pp. 1-4; Brennan and Rosen 2009, pp. 8-9; Karam et al. 2009; pp. 
2-3; Minckley and Marsh 2009, pp. 50-51; Paroz et al. 2009, pp. 12, 18; 
Robinson and Crowder 2009, pp. 3-5; Pilger et al. 2010, pp. 311-312; 
Stefferud et al. 2011, pp. 11-12; C. Akins 2012, pers. comm.; Young and 
Boyarski 2013, pp. 159-160; Emmons and Nowak 2013, p. 5).
The Decline of the Gartersnake Prey Base
    The documented decline of the northern Mexican and narrow-headed 
gartersnakes was typically subsequent to the declines in their prey 
base (native amphibian and fish populations). These declines in prey 
base result from predation following the establishment of nonnative 
bullfrogs, crayfish, and numerous species of nonnative, spiny-rayed 
fish as supported by an extensive body of literature referenced 
immediately above.
    Northern Mexican and narrow-headed gartersnakes appear to be 
particularly vulnerable to the loss of native prey species (Rosen and 
Schwalbe 1988, pp. 20, 44-45). Rosen et al. (2001, pp. 10, 13, 19) 
examined this issue in detail with respect to the northern Mexican 
gartersnake, and proposed two reasons for its decline following a loss 
of, or decline in, the native prey base: (1) The species is unlikely to 
increase foraging efforts at the risk of increased predation; and (2) 
the species needs adequate food on a regular basis to maintain its 
weight and health. If forced to forage more often for smaller prey 
items, a reduction in growth and reproductive rates can result (Rosen 
et al. 2001, pp. 10, 13). Rosen et al. (2001, p. 22) concluded that the 
presence and expansion of nonnative predators (mainly bullfrogs, 
crayfish, and green sunfish (Lepomis cyanellus)) is the primary cause 
of decline in northern Mexican gartersnakes and their prey in 
southeastern Arizona. In another example, Drummond and Marcias Garcia 
(1983, pp. 25, 30) found that Mexican gartersnakes fed primarily on 
frogs, and functioned as a local specialist in that regard. When frogs 
became unavailable, the species simply ceased major foraging 
activities. This led the author to conclude that frog abundance is 
probably the most important correlate, and main determinant, of 
foraging behavior in this species. Alternatively, terrestrial prey 
species were consumed, but the gartersnakes were never documented as 
having these prey items as a major dietary component, even when the 
gartersnakes were in dire need (Drummond and Marcias Garcia 1983, p. 
37).
    With respect to narrow-headed gartersnakes, the relationship 
between harmful nonnative species, a declining prey base, and 
gartersnake populations is clearly depicted in one population along Oak 
Creek. Nowak and Santana-Bendix (2002, Table 3) found a clear partition 
in the distribution of nonnative, spiny-rayed fish and soft-rayed fish 
in the vicinity of Midgely Bridge, where nonnative, spiny-rayed fish 
increased in abundance in the downstream direction and soft-rayed fish 
increased in abundance in the upstream direction. These fish community 
distributions closely parallel that of narrow-headed gartersnakes along 
Oak Creek, where gartersnake populations increase in density in the 
upstream direction and decrease notably in the downstream direction 
(Nowak and Santana-Bendix 2002, p. 23). Numerous historical records for 
narrow-headed gartersnakes document the species in the lower reach of 
Oak Creek, but the species is currently rarely detected in this reach 
of Oak Creek (Nowak and Santana-Bendix 2002, pp. 13-14), providing 
evidence of the decline of narrow-headed gartersnakes in the presence 
of nonnative, spiny-rayed fish.
    Fish--Northern Mexican and narrow-headed gartersnakes can 
successfully use nonnative, soft-rayed fish species as prey, including 
mosquitofish, red shiner, and introduced trout (Salmo sp.) (Nowak and 
Santana-Bendix 2002, pp. 24-25; Holycross et al. 2006, p. 23). However, 
all other nonnative species, most notably the spiny-rayed fish, are not 
considered prey species for northern Mexican or narrow-headed 
gartersnakes and, in addition, are known to prey on neonatal and 
juvenile gartersnakes. Nowak and Santana-Bendix (2002, p. 24) propose 
two hypotheses regarding the reluctance of narrow-headed gartersnakes 
to prey on nonnative, spiny-rayed fish: (1) The laterally-compressed 
shape and presence of sharp, spiny dorsal spines present a choking 
hazard to gartersnakes that has been observed to be fatal; and (2) 
nonnative, spiny-rayed fish tend to occupy the middle and upper zones 
in the water column, while narrow-headed gartersnakes typically hunt 
along the bottom (where native fish tend to occur). As a result, 
nonnative, spiny-rayed fish may be largely ecologically unavailable as 
prey. It is likely the shape and presence of sharp, spiny dorsal spines 
on these nonnative fish species also present a choking hazard to both 
northern Mexican and narrow-headed gartersnakes.
    Nonnative, spiny-rayed fish invasions can indirectly affect the 
health, maintenance, and reproduction of northern Mexican and narrow-
headed gartersnakes by altering their foraging strategy and 
compromising foraging success. Rosen et al. (2001, p. 19), in 
addressing the northern Mexican gartersnake, proposed that an increase 
in energy expended in foraging, coupled by the reduced number of small 
to

[[Page 41511]]

medium-sized prey fish available, results in deficiencies in nutrition, 
affecting growth and reproduction. This occurs because energy is 
allocated to maintenance and the increased energy costs of intense 
foraging activity, rather than to growth and reproduction. In contrast, 
a northern Mexican gartersnake diet that includes both fish and 
amphibians, such as leopard frogs, reduces the necessity to forage at a 
higher frequency, allowing metabolic energy gained from larger prey 
items to be allocated instead to growth and reproductive development. 
Myer and Kowell (1973, p. 225) experimented with food deprivation in 
common gartersnakes, and found significant reductions in lengths and 
weights of juvenile snakes that were deprived of regular feedings 
versus the control group that were fed regularly at natural 
frequencies. Reduced foraging success of both northern Mexican and 
narrow-headed gartersnakes means that individuals are likely to become 
vulnerable to effects from starvation, which may increase mortality 
rates of juveniles and, consequently, affect recruitment.
    Northern Mexican gartersnakes have a more varied diet than narrow-
headed gartersnakes. We are not aware of any studies that have 
addressed the direct relationship between prey base diversity and 
northern Mexican gartersnake recruitment and survivorship. However, 
Krause and Burghardt (2001, pp. 100-123) discuss the benefits and costs 
that may be associated with diet variability in the common gartersnake 
(Thamnophis sirtalis), an ecologically similar species to the northern 
Mexican gartersnake. Foraging for mixed-prey species may impede 
predator learning, as compared to specialization, on a certain prey 
species, but may also provide long-term benefits (Krause and Burghardt 
2001, p. 101). Krause and Burghardt (2001, p. 112) stated that varied 
predatory experience played an important role in the feeding abilities 
of gartersnakes through the first 8 months of age. These data suggest 
that a varied prey base might also be important for neonatal and 
juvenile northern Mexican gartersnakes (also a species with a varied 
diet) and that decreases in the diversity of the prey base during the 
young age classes might adversely affect the ability of individuals to 
capture prey throughout their lifespan, in addition to the more obvious 
effects of reduced prey availability.
    A wide variety of native fish species, now listed as endangered, 
threatened, or candidates for listing, were historically primary prey 
species for northern Mexican and narrow-headed gartersnakes (Rosen and 
Schwalbe 1988, pp. 18, 39). Aquatic habitat destruction and 
modification is often considered a leading cause for the decline in 
native fish in the southwestern United States. However, Marsh and Pacey 
(2005, p. 60) predict that despite the significant physical alteration 
of aquatic habitat in the southwest, native fish species could not only 
complete all of their life functions but could flourish in these 
altered environments, but for the presence of (harmful) nonnative fish 
species, as supported by a ``substantial and growing body of evidence 
derived from case studies.'' Northern Mexican and narrow-headed 
gartersnakes depend on native fish as a principle part of their prey 
base, although nonnative, soft-rayed fish are also common prey items 
where they overlap in distribution with these gartersnakes (Nowak and 
Santana-Bendix 2002, pp. 24-25; Holycross et al. 2006, p. 23). 
Nonnative, spiny-rayed fish compete with northern Mexican and narrow-
headed gartersnakes for prey. In their extensive surveys, Rosen and 
Schwalbe (1988, p. 44) only found narrow-headed gartersnakes in 
abundance where native fish species predominated, but did not find them 
abundant in the presence of robust nonnative, spiny-rayed fish 
populations. Minckley and Marsh (2009, pp. 50-51) found nonnative 
fishes to be the single-most significant factor in the decline of 
native fish species and also their primary obstacle to recovery. Of the 
48 conterminous States in the United States, Arizona has the highest 
proportion of nonnative fish species (66 percent) represented by 
approximately 68 species of nonnative fish (Turner and List 2007, p. 
13).
    Collier et al. (1996, p. 16) note that interactions between native 
and nonnative fish have significantly contributed to the decline of 
many native fish species from direct predation and, indirectly, from 
competition (which has adversely affected the prey base for northern 
Mexican and narrow-headed gartersnakes). The AGFD considers native fish 
in Arizona as the most threatened taxa among the State's native 
species, largely as a result of predation and competition with 
nonnative species (AGFD 2006, p. 83). Holycross et al. (2006, pp. 52-
61) documented significantly depressed or extirpated native fish prey 
bases for northern Mexican and narrow-headed gartersnakes along the 
Mogollon Rim in Arizona and New Mexico. Rosen et al. (2001, Appendix I) 
documented the decline of several native fish species in several 
locations visited in southeastern Arizona, further affecting the prey 
base of northern Mexican gartersnakes in that area.
    Stocked for sport, forage, or biological control, nonnative fishes 
have been shown to become invasive where released, do not require 
natural flow regimes, and tend to be more phylogenetically advanced 
than native species (Kolar et al. 2003, p. 9) which contributed to 
their expansion in the Gila River basin. Harmful nonnative fish species 
tend to be nest-builders and actively guard their young which may 
provide them another ecological advantage over native species which are 
broadcast spawners and provide no parental care to their offspring 
(Marsh and Pacey 2005, p. 60). It is therefore likely that recruitment 
and survivorship is greater in nonnative species than native species 
where they overlap, providing them with an ecological advantage. Table 
2-1 in Kolar et al. (2003, p. 10) provides a map depicting the high 
degree of overlap in the distribution of native and nonnative fishes 
within the Gila River basin of Arizona and New Mexico as well as 
watersheds thought to be dominated by nonnative fish species. The 
widespread decline of native fish species from the arid southwestern 
United States and Mexico has resulted largely from interactions with 
nonnative species and has been captured in the listing rules of 13 
native species listed under the Act, and whose historical ranges 
overlap with the historical distribution of northern Mexican and 
narrow-headed gartersnakes. Native fish species that were likely prey 
species for these gartersnakes and are now listed under the Act, 
include the bonytail chub (Gila elegans, 45 FR 27710, April 23, 1980), 
Yaqui catfish (Ictalurus pricei, 49 FR 34490, August 31, 1984), Yaqui 
chub (Gila purpurea, 49 FR 34490, August 31, 1984), Yaqui topminnow 
(Poeciliopsis occidentalis sonoriensis, 32 FR 4001, March 11, 1967), 
beautiful shiner (Cyprinella formosa, 49 FR 34490, August 31, 1984), 
humpback chub (Gila cypha, 32 FR 4001, March 11, 1967), Gila chub (Gila 
intermedia, 70 FR 66663, November 2, 2005), Colorado pikeminnow 
(Ptychocheilus lucius, 32 FR 4001, March 11, 1967), spikedace (Meda 
fulgida, 77 FR 10810, February 23, 2012), loach minnow (Tiaroga 
cobitis, 77 FR 10810, February 23, 2012), razorback sucker (Xyrauchen 
texanus, 56 FR 54957, October 23, 1991), desert pupfish (Cyprinodon 
macularius, 51 FR 10842, March 31, 1986), and Gila topminnow 
(Poeciliopsis occidentalis, 32 FR 4001, March 11, 1967). In total, 
within Arizona, 19 of 31 (61 percent) native

[[Page 41512]]

fish species are listed under the Act. Arizona ranks the highest of all 
50 States in the percentage of native fish species with declining 
trends (85.7 percent) and New Mexico ranks sixth (48.1 percent) (Stein 
2002, p. 21; Warren and Burr 1994, p. 14). Recovery of native fishes in 
the Southwest has been fraught with complicating factors, both natural 
and sociopolitical, which have presented significant challenges to the 
recovery of many imperiled native fish species (Minckley and Marsh 
2009, pp. 52-53), including many that are important prey species for 
the northern Mexican and narrow-headed gartersnakes.
    In an evolutionary context, many native fishes co-evolved with very 
few predatory fish species, whereas most of the nonnative species co-
evolved with many predatory species (Clarkson et al. 2005, p. 21). A 
contributing factor to the decline of native fish species cited by 
Clarkson et al. (2005, p. 21) is that most of the nonnative species 
evolved behaviors, such as nest guarding, to protect their offspring 
from these many predators, while native species are generally broadcast 
spawners that provide no parental care. In the presence of nonnative 
species, the reproductive behaviors of native fish fail to allow them 
to compete effectively with the nonnative species, and, as a result, 
the viability of native fish populations is reduced.
    Olden and Poff (2005, p. 75) stated that environmental degradation 
and the proliferation of nonnative fish species threaten the highly 
localized and unique fish faunas of the American Southwest. The fastest 
expanding nonnative species are red shiner (Cyprinella lutrensis), 
fathead minnow (Pimephales promelas), green sunfish, largemouth bass 
(Micropterus salmoides), western mosquitofish, and channel catfish 
(Ictalurus punctatus). These species are considered to be the most 
invasive in terms of their negative impacts on native fish communities 
(Olden and Poff 2005, p. 75). Many nonnative fishes, in addition to 
those listed immediately above, including yellow and black bullheads 
(Ameiurus sp.), flathead catfish (Pylodictis olivaris), and smallmouth 
bass (Micropterus dolomieu), have been introduced into formerly and 
currently occupied northern Mexican or narrow-headed gartersnake 
habitat and are predators on these species and their prey (Bestgen and 
Propst 1989, pp. 409-410; Marsh and Minckley 1990, p. 265; Sublette et 
al. 1990, pp. 112, 243, 246, 304, 313, 318; Abarca and Weedman 1993, 
pp. 6-12; Stefferud and Stefferud 1994, p. 364; Weedman and Young 1997, 
pp. 1, Appendices B, C; Rinne et al. 1998, pp. 3-6; Voeltz 2002, p. 88; 
Bonar et al. 2004, pp. 1-108; Fagan et al. 2005, pp. 34, 38-39, 41; 
Probst et al. 2008, pp. 1242-1243). Nonnative, spiny-rayed fish 
species, such as flathead catfish, may be especially dangerous to 
narrow-headed gartersnake populations through competition and direct 
predation, because they are primarily piscivorous (fish-eating) (Pilger 
et al. 2010, pp. 311-312), have large mouths, and have a tendency to 
occur along the stream bottom, where narrow-headed gartersnakes 
principally forage.
    Rosen et al. (2001, Appendix I) and Holycross et al. (2006, pp. 15-
51) conducted large-scale surveys for northern Mexican gartersnakes in 
southeastern and central Arizona and narrow-headed gartersnakes in 
central and east-central Arizona, and documented the presence of 
nonnative fish at many locations. Holycross et al. (2006, pp. 14-15) 
found nonnative fish species in 64 percent of the sample sites in the 
Agua Fria subbasin, 85 percent of the sample sites in the Verde River 
subbasin, 75 percent of the sample sites in the Salt River subbasin, 
and 56 percent of the sample sites in the Gila River subbasin. In 
total, nonnative fish were observed at 41 of the 57 sites surveyed (72 
percent) across the Mogollon Rim (Holycross et al. 2006, p. 14). 
Entirely native fish communities were detected in only 8 of 57 sites 
surveyed (14 percent) (Holycross et al. 2006, p. 14). It is well 
documented that nonnative fish have now infiltrated the majority of 
aquatic communities in the southwestern United States as depicted in 
Tables 1 and 2, above, as well as in Appendix A (available at http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071).
    Several authors have identified both the presence of nonnative fish 
as well as their deleterious effects on native species within Arizona. 
Many areas have seen a shift from a predominance of native fishes to a 
predominance of nonnative fishes. On the upper Verde River, native 
species dominated the total fish community at greater than 80 percent 
from 1994 to 1996, before dropping to approximately 20 percent in 1997 
and 19 percent in 2001. At the same time, three nonnative species 
increased in abundance between 1994 and 2000 (Rinne et al. 2004, pp. 1-
2). In an assessment of the Verde River, Bonar et al. (2004, p. 57) 
found that in the Verde River mainstem, nonnative fishes were 
approximately 2.6 times more dense per unit volume of river than native 
fishes, and their populations were approximately 2.8 times that of 
native fishes per unit volume of river. Haney et al. (2008, p. 61) 
declared the northern Mexican gartersnake as nearly lost from the Verde 
River but also suggested that diminished river flow may be an important 
factor. Similar changes in the dominance of nonnative fishes have 
occurred on the Middle Fork Gila River, with a 65 percent decline of 
native fishes between 1988 and 2001 (Propst 2002, pp. 21-25). Abarca 
and Weedman (1993, pp. 6-12) found that the number of nonnative fish 
species was twice the number of native fish species in Tonto Creek in 
the early 1990s, with a stronger nonnative species influence in the 
lower reaches, where the northern Mexican gartersnake is considered to 
still occur, and Burger (2008, p. 8) confirmed their continued 
existence there. Surveys in the Salt River above Lake Roosevelt 
indicate a decline of roundtail chub and other natives with an increase 
in flathead and channel catfish numbers (Voeltz 2002, p. 49).
    In New Mexico, nonnative fish have been identified as the main 
cause for declines observed in native fish populations (Voeltz 2002, p. 
40; Probst et al. 2008, pp. 1242-1243). Fish experts from the U.S. 
Forest Service, U.S. Bureau of Reclamation, U.S. Bureau of Land 
Management (BLM), University of Arizona, Arizona State University, the 
Nature Conservancy, and others declared the native fish fauna of the 
Gila River basin to be critically imperiled, and they cite habitat 
destruction and nonnative species as the primary factors for the 
declines. They call for the control and removal of nonnative fish as an 
overriding need to prevent the decline, and ultimate extinction, of 
native fish species within the basin (DFT 2003, p. 1). In some areas, 
nonnative fishes may not dominate the system, but their abundance has 
increased. This is the case for the Cliff-Gila Valley area of the Gila 
River, where nonnative fishes increased from 1.1 percent to 8.5 
percent, while native fishes declined steadily over a 40-year period 
(Propst et al. 1986, pp. 27-32). At the Redrock and Virden valleys on 
the Gila River, the relative abundance in nonnative fishes in the same 
time period increased from 2.4 percent to 17.9 percent (Propst et al. 
1986, pp. 32-34). Four years later, the relative abundance of nonnative 
fishes increased to 54.7 percent at these sites (Propst et al. 1986, 
pp. 32-36). The percentage of nonnative fishes increased by almost 12 
percent on the Tularosa River between 1988 and 2003, while on the East 
Fork Gila River, nonnative fishes increased to 80.5 percent relative 
abundance in 2003 (Propst 2005, pp. 6-7, 23-24).

[[Page 41513]]

Nonnative fishes are also considered a management issue in other areas 
including Eagle Creek, the San Pedro River, West Fork Gila River, and 
to a lesser extent, the Blue River.
    In addition to harmful nonnative species, various parasites may 
affect native fish species that are prey for northern Mexican and 
narrow-headed gartersnakes. Asian tapeworm was introduced into the 
United States with imported grass carp (Ctenopharyngodon idella) in the 
early 1970s. It has since become well established in areas throughout 
the southwestern United States. The definitive host in the life cycle 
of Asian tapeworm is a cyprinid fish (carp or minnow), and therefore it 
is a potential threat to native cyprinids in Arizona and New Mexico. 
The Asian tapeworm adversely affects fish health by impeding the 
digestion of food as it passes through the digestive track. Emaciation 
and starvation of the host can occur when large enough numbers of worms 
feed off the fish directly. An indirect effect is that weakened fish 
are more susceptible to infection by other pathogens. Asian tapeworm 
invaded the Gila River basin and was found during the Central Arizona 
Project's fall 1998 monitoring in the Gila River at Ashurst-Hayden Dam. 
It has also been confirmed from Bonita Creek in 2010 (USFWS National 
Wild Fish Health Survey 2010). This parasite can infect many species of 
fish and is carried into new areas along with nonnative fishes or 
native fishes from contaminated areas.
    Another parasite (Ichthyophthirius multifiliis) (Ich) usually 
occurs in deep waters with low flow and is a potential threat to native 
fish. Ich has occurred in some Arizona streams, probably encouraged by 
high temperatures and crowding as a result of drought. This parasite 
was observed being transmitted on the Sonora sucker (Catostomus 
insignis), although it does not appear to be host-specific and could be 
transmitted by other species (Mpoame 1982, p. 46). It has been found on 
desert and Sonoran suckers, as well as roundtail chub (Robinson et al. 
1998, p. 603), which are important prey species for the northern 
Mexican and narrow-headed gartersnakes. This parasite becomes embedded 
under the skin and within the gill tissues of infected fish. When Ich 
matures, it leaves the fish, causing fluid loss, physiological stress, 
and sites that are susceptible to infection by other pathogens. If Ich 
is present in large enough numbers, it can also impact respiration 
because of damaged gill tissue.
    Anchor worm (Lernaea cyprinacea), an external parasite, is unusual 
in that it has little host specificity, infecting a wide range of 
fishes and amphibians. Infection by this parasite has been known to 
kill large numbers of fish due to tissue damage and secondary infection 
of the attachment site (Hoffnagle and Cole 1999, p. 24). Presence of 
this parasite in the Gila River basin is a threat to native fishes. In 
July 1992, the BLM found anchor worms in Bonita Creek. They have also 
been documented in the Verde River (Robinson et al. 1998, pp. 599, 603-
605).
    The yellow grub (Clinostomum marginatum) is a parasitic, larval 
flatworm that appears as yellow spots on the body and fins of a fish. 
Because the intermediate host is a bird and therefore highly mobile, 
yellow grubs are easily spread. When yellow grubs infect a fish, they 
penetrate the skin and migrate into its tissues, causing damage and 
potentially hemorrhaging. Damage from one yellow grub may be minimal, 
but in greater numbers, yellow grubs can kill fish (Maine Department of 
Inland Fisheries and Wildlife 2002a, p. 1). Yellow grubs occur in many 
areas in Arizona and New Mexico, including Oak Creek (Mpoame and Rinne 
1983, pp. 400-401), the Salt River (Amin 1969, p. 436; Bryan and 
Robinson 2000, p. 19), the Verde River (Bryan and Robinson 2000, p. 
19), and Bonita Creek (Robinson 2011, pers. comm.).
    The black grub (Neascus spp.), also called black spot, is a 
parasitic larval fluke that appears as black spots on the skin, tail 
base, fins, and musculature of a fish. When an intermediate life stage 
of black grubs migrates into the tissues of a fish they are called 
``cercaria.'' The damage caused by one cercaria is negligible, but in 
greater numbers they may kill a fish (Lane and Morris 2000, pp. 2-3; 
Maine Department of Inland Fisheries and Wildlife 2002b, p. 1). Black 
grubs are present in the Verde River (Robinson et al. 1998, p. 603; 
Bryan and Robinson 2000, p. 21), and are prevalent in the San Francisco 
River in New Mexico (Paroz 2011, pers. comm.).
    To date, we have no information on the effect of parasite 
infestation in native fish on both gartersnake populations.
    The Decline of Native Fish Communities in Mexico--The first 
tabulations of freshwater fish species at risk in Mexico occurred in 
1961, when 11 species were identified as being at risk (Contreras-
Balderas et al. 2003, p. 241). As of 2003, of the 506 species of 
freshwater fish recorded in Mexico, 185 (37 percent) have been listed 
by the Mexican Federal Government as either endangered, facing 
extinction, under special protection, or likely extinct (Alvarez-Torres 
et al. 2003, p. 323), almost a 17-fold increase in slightly over four 
decades; 25 species are believed to have gone extinct (Contreras-
Balderas et al. 2003, p. 241). In the lower elevations of Mexico, 
within the distribution of the northern Mexican gartersnake, there are 
approximately 200 species of native freshwater fish documented, with 
120 native species under some form of threat and an additional 15 that 
have gone extinct (Contreras-Balderas and Lozano 1994, pp. 383-384). 
The Fisheries Law in Mexico empowered the country's National Fisheries 
Institute to compile and publish the National Fisheries Chart in 2000, 
which found that Mexico's fish fauna has seriously deteriorated as a 
result of environmental impacts (pollution), water basin degradation 
(dewatering, siltation), and the introduction of nonnative species 
(Alvarez-Torres et al. 2003, pp. 320, 323). The National Fisheries 
Chart is regarded as the first time the Mexican government has openly 
revealed the status of its freshwater fisheries and described their 
management policies (Alvarez-Torres et al. 2003, pp. 323-324).
    Industrial, municipal, and agricultural water pollution, dewatering 
of aquatic habitat, and the proliferation nonnative species are widely 
considered to be the greatest threats to freshwater ecosystems in 
Mexico (Branson et al. 1960, p. 218; Conant 1974, pp. 471, 487-489; 
Miller et al. 1989, pp. 25-26, 28-33; 2005, pp. 60-61; DeGregorio 1992, 
p. 60; Contreras Balderas and Lozano 1994, pp. 379-381; Lyons et al. 
1995, p. 572; 1998, pp. 10-12; va Landa et al. 1997, p. 316; Mercado-
Silva et al. 2002, p. 180; Contreras-Balderas et al. 2003, p. 241; 
Dom[iacute]nguez-Dom[iacute]nguez et al. 2007, Table 3). A shift in 
land use policies in Mexico to encourage free market principles in 
rural, small-scale agriculture has been found to promote land use 
practices that threaten local biodiversity (Ortega-Huerta and Kral 
2007, p. 2; Randall 1996, pp. 218-220; Kiernan 2000, pp. 13-23). These 
threats have been documented throughout the distribution of the 
northern Mexican gartersnake in Mexico and are best represented in the 
scientific literature in the context of fisheries studies. Contreras-
Balderas et al. (2003, pp. 241, 243) named Chihuahua (46 species), 
Coahuila (35 species), Sonora (19 species), and Durango (18 species) as 
Mexican states that had some of the most reports of freshwater fish 
species at risk. These states are all within the distribution of the 
northern Mexican gartersnake, indicating an overlapping trend of 
declining prey bases and

[[Page 41514]]

threatened ecosystems within the range of the northern Mexican 
gartersnake in Mexico. Contreras-Balderas et al. (2003, Appendix 1) 
found various threats to be adversely affecting the status of 
freshwater fish and their habitat in several states in Mexico: (1) 
Habitat reduction or alteration (Sonora, Chihuahua, Durango, Coahuila, 
San Luis Potos[iacute], Jalisco, Guanajuato); (2) water depletion 
(Chihuahua, Durango, Coahuila, Sonora, Guanajuato, Jalisco, San Luis 
Potos[iacute]); (3) harmful nonnative species (Durango, Chihuahua, 
Coahuila, San Luis Potos[iacute], Sonora, Veracruz); and (4) pollution 
(M[eacute]xico, Jalisco, Chihuahua, Coahuila, Durango). Within the 
states of Chihuahua, Durango, Coahuila, Sonora, Jalisco, and 
Guanajuato, water depletion is considered serious, with entire basins 
having been dewatered, or conditions have been characterized as 
``highly altered'' (Contreras-Balderas et al. 2003, Appendix 1). All of 
the Mexican states with the highest numbers of fish species at risk are 
considered arid, a condition hastened by increasing desertification 
(Contreras-Balderas et al. 2003, p. 244).
    Aquaculture and Nonnative Fish Proliferation in Mexico--Nonnative 
fish compete with and prey upon northern Mexican gartersnakes and their 
native prey species. The proliferation of nonnative fish species 
throughout Mexico happened mainly by natural dispersal, intentional 
stockings, and accidental breaches of artificial or constructed 
barriers by nonnative fish. Lentic water bodies such as lakes, 
reservoirs, and ponds are often used for flood control, agricultural 
purposes, and most commonly to support commercial fisheries. The most 
recent estimates indicate that Mexico has 13,936 of such water bodies, 
where approximately 96 percent are between 2.47-247 acres (1-100 
hectares) and approximately half are artificial (Sugunan 1997, Table 
8.3; Alvarez-Torres et al. 2003, pp. 318, 322). Areas where these 
landscape features are most prevalent occur within the distribution of 
the northern Mexican gartersnake. For example, Jalisco and Zacatecas 
are listed as two of four states with the highest number of reservoirs, 
and Chihuahua is one of two states known for a high concentration of 
lakes (Sugunan 1997, Section 8.4.2). Based on the data presented in 
Sugunan (1997, Table 8.5), a total of 422 dammed reservoirs are located 
within the 16 Mexican states where the northern Mexican gartersnake is 
thought to occur. Mercado-Silva et al. (2006, p. 534) found that within 
the state of Guanajuato, ``Practically all streams and rivers in the 
[Laja] basin are truncated by reservoirs or other water extraction and 
storage structures.'' On the Laja River alone, there are two major 
reservoirs and a water diversion dam; 12 more reservoirs are located on 
its tributaries (Mercado-Silva et al. 2006, p. 534). As a consequence 
of dam operations, the main channel of the Laja remains dry for 
extensive periods of time (Mercado-Silva et al. 2006, p. 541). The 
damming and modification of the lower Colorado River in Mexico, where 
the northern Mexican gartersnake occurred, has facilitated the 
replacement of the entire native fishery with nonnative species (Miller 
et al. 2005, p. 61). Each reservoir created by a dam is either managed 
as a nonnative commercial fishery or has become a likely source 
population of nonnative species, which have naturally or artificially 
colonized the reservoir, dispersed into connected riverine systems, and 
damaged native aquatic communities.
    Mexico, as with other developing countries, depends in large part 
on freshwater commercial fisheries as a source of protein for both 
urbanized and rural human populated areas. Commercial and subsistence 
fisheries rely heavily on introduced, nonnative species in the largest 
freshwater lakes (Soto-Galera et al. 1999, p. 133) down to rural, small 
ponds (Tapia and Zambrano 2003, p. 252). At least 87 percent of the 
species captured or cultivated in inland fisheries of Mexico from 1989-
1999 included tilapia, common carp, channel catfish, trout, and black 
bass (Micropterus sp.), all of which are nonnative (Alvarez-Torres et 
al. 2003, pp. 318, 322). In fact, the northern and central plateau 
region of Mexico (which comprises most of the distribution of the 
northern Mexican gartersnake's distribution in Mexico) is considered 
ideal for the production of harmful, predatory species such as bass and 
catfish (Sugunan 1997, Section 8.3). Largemouth bass are now produced 
and stocked in reservoirs and lakes throughout the distribution of the 
northern Mexican gartersnake (Sugunan 1997, Section 8.8.1). The 
Secretariat for Environment, Natural Resources and Fisheries, formed in 
1995 and known as SEMARNAP, is the Mexican federal agency responsible 
for management of the country's environment and natural resources. 
SEMARNAP dictates the stocking rates of nonnative species into the 
country's lakes and reservoirs. For example, the permitted stocking 
rate for largemouth bass in Mexico is one fish per square meter in 
large reservoirs (Sugunan 1997, Table 8.8); therefore, a 247-acre (100-
ha) reservoir could be stocked with 1,000,000 largemouth bass. The 
common carp, the subject of significant aquaculture investment since 
the 1960s in Mexico, is known for altering aquatic habitat and 
consuming the eggs and fry of native fish species, and is now 
established in 95 percent of Mexico's freshwater systems (Tapia and 
Zambrano 2003, p. 252).
    Basins in northern Mexico, such as the Rio Yaqui, have been found 
to be significantly compromised by harmful nonnative fish species. 
Unmack and Fagan (2004, p. 233) compared historical museum collections 
of nonnative fish species from the Gila River basin in Arizona and the 
Yaqui River basin in Sonora, Mexico, to gain insight into the trends in 
distribution, diversity, and abundance of nonnative fishes in each 
basin over time. They found that nonnative species are slowly, but 
steadily, increasing in all three parameters in the Yaqui Basin (Unmack 
and Fagan 2004, p. 233). Unmack and Fagan (2004, p. 233) predicted 
that, in the absence of aggressive management intervention, significant 
extirpations or range reductions of native fish species are expected to 
occur in the Yaqui Basin of Sonora, Mexico, which may have extant 
populations of the northern Mexican gartersnake, as did much of the 
Gila Basin before the introduction of nonnative species. Loss of native 
fishes will impact prey availability for the northern Mexican 
gartersnake and threaten its persistence in these areas. Black 
bullheads (Ameiurus melas) were reported as abundant, and common carp 
were detected from the Rio Yaqui in southern Sonora, Mexico (Branson et 
al. 1960, p. 219). Bluegill (Lepomis macrochirus) were also reported at 
this location, representing a significant range expansion that the 
authors expected was the result of escaping nearby farm ponds or 
irrigation ditches (Branson et al. 1960, p. 220). Largemouth bass, 
green sunfish, and an undetermined crappie species have also been 
reported from this area (Branson et al. 1960, p. 220). Hendrickson and 
Varela-Romero (1989, p. 479) conducted fish sampling along the 
R[iacute]o Sonoyta of northern Sonora, Mexico, and found over half of 
the fish collected were nonnative, both predatory species and prey 
species for the northern Mexican gartersnake.
    Dom[iacute]nguez-Dom[iacute]nguez et al. (2007, p. 171) sampled 52 
localities for a rare freshwater fish, the Picotee goodeid 
(Zoogoneticus quitzeoensis), along the southern portion of the Mesa 
Central (Mexican Plateau) of Mexico and found 21 localities had 
significant signs of pollution. Of the 29 localities where the target 
species was detected, 28 of them also had harmful nonnative species

[[Page 41515]]

present, such as largemouth bass, cichlids (Oreochromis sp.), bluegill, 
P[aacute]tzcuaro chub (Algansea lacustris) (Dom[iacute]nguez-
Dom[iacute]nguez et al. 2007, pp. 171, Table 3). Other nonnative fish 
species reported are soft-rayed and small bodied, and may be prey items 
for younger age classes of northern Mexican gartersnakes. Several 
examples of significant aquatic habitat degradation or destruction were 
also observed by Dom[iacute]nguez-Dom[iacute]nguez et al. (2007, Table 
3) in this region of Mexico, including the draining of natural lakes 
and cienegas for conversion to agricultural purposes, modification of 
springs for recreational swimming, diversions, and dam construction. As 
of 2006, native fish species comprised the most prevalent in species 
composition and abundance in the Laja Basin; however the basin is 
trending towards a nonnative fishery based on historical data whereas 
nonnative species were most recently collected from 16 of 17 sample 
sites, largemouth bass have significantly expanded their distribution 
within the headwaters of the basin, and bluegill are now widespread in 
the Laja River (Mercado-Silva et al. 2006, pp. 537, 542, Table 4).
    The ecological risk of nonnative, freshwater aquaculture production 
has only recently been acknowledged by the Mexican government as 
compared to decades of aquaculture production, mainly because 
conservation of biodiversity was not valued as highly as the benefits 
garnered by nonnative fish production, most notably in the country's 
rural, poorest regions (Tapia and Zambrano 2003, p. 252). In fact, 
recent amendments to Mexico's fishing regulations allow for relaxation 
of existing regulations imposed by other government regulations and 
expansion of opportunities for investment in commercial fishing to 
promote growth in Mexico's aquaculture sector (Sugunan 1997, Section 
8.7.1). Between the broad geographic extent of commercial or sustenance 
fisheries, the important source of protein they represent, and the many 
mechanisms introduced nonnative fish have to naturally or artificially 
expand their distribution, few areas within the range of the northern 
Mexican gartersnake in Mexico have avoided adverse impacts associated 
with nonnative species. Harmful nonnative fish species therefore pose a 
significant threat to the prey base of northern Mexican gartersnakes 
and to the gartersnakes themselves throughout most of their range in 
Mexico.
    Amphibian decline--Matthews et al. (2002, p. 16) examined the 
relationship of gartersnake distributions, amphibian population 
declines, and nonnative fish introductions in high-elevation aquatic 
ecosystems in California. Matthews et al. (2002, p. 16) specifically 
examined the effect of nonnative trout introductions on populations of 
amphibians and mountain gartersnakes (Thamnophis elegans elegans). 
Their results indicated the probability of observing gartersnakes was 
30 times greater in lakes containing amphibians than in lakes where 
amphibians have been extirpated by nonnative fish. These results 
supported a prediction by Jennings et al. (1992, p. 503) that native 
amphibian declines will lead directly to gartersnake declines. Matthews 
et al. (2002, p. 20) noted that, in addition to nonnative fish species 
adversely impacting amphibian populations that are part of the 
gartersnake's prey base, direct predation on gartersnakes by nonnative 
fish also occurs. However, Shah et al. (2010, pp. 188-190) found that 
native tadpoles may exhibit anti-predator learning behavior that may 
assist their persistence in habitat affected by nonnative, spiny-rayed 
fish.
    Declines in the native leopard frog populations in Arizona have 
contributed to declines in the northern Mexican gartersnake, one of the 
frog's primary native predators. Native ranid frog species, such as 
lowland leopard frogs, northern leopard frogs, and federally threatened 
Chiricahua leopard frogs, have all experienced declines in various 
degrees throughout their distribution in the Southwest, partially due 
to predation and competition with nonnative species (Clarkson and 
Rorabaugh 1989, pp. 531, 535; Hayes and Jennings 1986, p. 490). Rosen 
et al. (1995, pp. 257-258) found that Chiricahua leopard frog 
distribution in the Chiricahua Mountain region of Arizona was inversely 
related to nonnative species distribution and, without corrective 
action, predicted that the Chiricahua leopard frog may be difficult to 
conserve in this region. Along the Mogollon Rim, Holycross et al. 
(2006, p. 13) found that only 8 sites of 57 surveyed (15 percent) 
consisted of an entirely native anuran community, and that native frog 
populations in another 19 sites (33 percent) had been completely 
displaced by invading bullfrogs. However, such declines in native frog 
populations are not necessarily irreversible. Ranid frog populations 
have been shown to rebound strongly when nonnative fish are removed 
(Knapp et al. 2007, pp. 15-18).
    Scotia Canyon, in the Huachuca Mountains of southeastern Arizona, 
is a location where corresponding declines of leopard frog and northern 
Mexican gartersnake populations have been documented through repeated 
survey efforts over time (Holm and Lowe 1995, p. 33). Surveys of Scotia 
Canyon occurred during the early 1980s, and again during the early 
1990s. Leopard frogs in Scotia Canyon were infrequently observed during 
the early 1980s, and were apparently extirpated by the early 1990s 
(Holm and Lowe 1995, pp. 45-46). Northern Mexican gartersnakes were 
observed in decline during the early 1980s, with low capture rates 
continuing through the early 1990s (Holm and Lowe 1995, pp. 27-35). 
Surveys documented further decline of leopard frogs and northern 
Mexican gartersnakes in 2000 (Rosen et al. 2001, pp. 15-16).
    A former large, local population of northern Mexican gartersnakes 
at the San Bernardino National Wildlife Refuge (SBNWR) in southeastern 
Arizona has also experienced a correlative decline of leopard frogs, 
and northern Mexican gartersnakes are now thought to occur at very low-
population densities or may be extirpated there (Rosen and Schwalbe 
1988, p. 28; 1995, p. 452; 1996, pp. 1-3; 1997, p. 1; 2002b, pp. 223-
227; 2002c, pp. 31, 70; Rosen et al. 1996b, pp. 8-9; 2001, pp. 6-10).
    Survey data indicate that declines of leopard frog populations, 
often correlated with nonnative species introductions, the spread of a 
chytrid fungus (Batrachochytrium dendrobatidis, Bd), and habitat 
modification and destruction, have occurred throughout much of the 
northern Mexican gartersnake's U.S. distribution (Nickerson and Mays 
1970, p. 495; Vitt and Ohmart 1978, p. 44; Ohmart et al. 1988, p. 150; 
Rosen and Schwalbe 1988, Appendix I; 1995, p. 452; 1996, pp. 1-3; 1997, 
p. 1; 2002b, pp. 232-238; 2002c, pp. 1, 31; Clarkson and Rorabaugh 
1989, pp. 531-538; Sredl et al. 1995a, pp. 7-8; 1995b, pp. 8-9, 1995c, 
pp. 7-8; 2000, p. 10; Holm and Lowe 1995, pp. 45-46; Rosen et al. 
1996b, p. 2; 2001, pp. 2, 22; Degenhardt et al. 1996, p. 319; Fernandez 
and Rosen 1996, pp. 6-20; Drost and Nowak 1997, p. 11; Turner et al. 
1999, p. 11; Nowak and Spille 2001, p. 32; Holycross et al. 2006, pp. 
13-14, 52-61). Specifically, Holycross et al. (2006, pp. 53-57, 59) 
documented potential extirpations of the northern Mexican gartersnake's 
native leopard frog prey base at several currently, historically, or 
potentially occupied locations, including the Agua Fria River in the 
vicinity of Table Mesa Road and Little Grand Canyon Ranch, and at Rock 
Springs, Dry Creek from Dugas Road to Little Ash Creek, Little Ash 
Creek from Brown Spring to Dry Creek, Sycamore Creek (Agua Fria

[[Page 41516]]

subbasin) in the vicinity of the Forest Service Cabin, the Page Springs 
and Bubbling Ponds fish hatchery along Oak Creek, Sycamore Creek (Verde 
River subbasin) in the vicinity of the confluence with the Verde River 
north of Clarkdale, along several reaches of the Verde River mainstem, 
Cherry Creek on the east side of the Sierra Ancha Mountains, and Tonto 
Creek from Gisela to ``the Box,'' near its confluence with Rye Creek.
    Rosen et al. (2001, p. 22) identified the expansion of bullfrogs 
into the Sonoita grasslands, which contain occupied northern Mexican 
gartersnake habitat, and the introduction of crayfish into Lewis 
Springs, as being of particular concern in terms of future recovery 
efforts for the northern Mexican gartersnake. Rosen et al. (1995, pp. 
252-253) sampled aquatic herpetofauna at 103 sites in the Chiricahua 
Mountains region, which included the Chiricahua, Dragoon, and 
Peloncillo mountains, and the Sulphur Springs, San Bernardino, and San 
Simon valleys. They found that 43 percent of all cold-blooded aquatic 
and semi-aquatic vertebrate species detected were nonnative. The most 
commonly encountered nonnative species was the bullfrog (Rosen et al. 
1995, p. 254). Witte et al. (2008, p. 1) found that the disappearance 
of ranid frog populations in Arizona were 2.6 times more likely in the 
presence of crayfish. Witte et al. (2008, p. 7) emphasized the 
significant influence of nonnative species on the disappearance of 
ranid frogs in Arizona.
    In addition to harmful nonnative species, disease and nonnative 
parasites have been implicated in the decline of the prey base of the 
northern Mexican gartersnake. In particular, the outbreak of 
chytridiomycosis or ``Bd,'' a skin fungus, has been identified as a 
chief causative agent in the significant declines of many of the native 
ranid frogs and other amphibian species. In addition, regional concerns 
exist for the native fish community due to nonnative parasites, such as 
the Asian tapeworm (Bothriocephalus acheilognathi) in southeastern 
Arizona (Rosen and Schwalbe 1997, pp. 14-15; 2002c, pp. 1-19; Morell 
1999, pp. 728-732; Sredl and Caldwell 2000, p. 1; Hale 2001, pp. 32-37; 
Bradley et al. 2002, p. 206). As indicated, Bd has been implicated in 
both large-scale declines and local extirpations of many amphibians, 
chiefly anuran species, around the world (Johnson 2006, p. 3011). Lips 
et al. (2006, pp. 3166-3169) suggest that the high virulence and large 
number of potential hosts make Bd a serious threat to amphibian 
diversity. In Arizona, Bd infections have been reported in several of 
the native prey species of the northern Mexican gartersnake within the 
distribution of the snake (Morell 1999, pp. 731-732; Sredl and Caldwell 
2000, p. 1; Hale 2001, pp. 32-37; Bradley et al. 2002, p. 207; USFWS 
2002, pp. 40802-40804; USFWS 2007, pp. 26, 29-32). Declines of native 
prey species of the northern Mexican gartersnake from Bd infections 
have contributed to the decline of this species in the United States 
(Morell 1999, pp. 731-732; Sredl and Caldwell 2000, p. 1; Hale 2001, 
pp. 32-37; Bradley et al. 2002, p. 207; USFWS 2002, pp. 40802-40804; 
USFWS 2007, pp. 26, 29-32). Evidence of Bd-related amphibian declines 
has been confirmed in portions of southern Mexico (just outside the 
range of northern Mexican gartersnakes), and data suggest declines are 
more prevalent at higher elevations (Lips et al. 2004, pp. 560-562). 
However, much less is known about the role of Bd in amphibian declines 
across much of Mexico, in particular the mountainous regions of Mexico 
(including much of the range of northern Mexican gartersnakes in 
Mexico) as the region is significantly understudied (Young et al. 2000, 
p. 1218). Because narrow-headed gartersnakes feed on fish, Bd has not 
affected their prey base. Also, research shows that the fungus 
Batrachochytrium can grow on boiled snakeskin (keratin) in the 
laboratory (Longcore et al. 1999, p. 227), indicating the potential for 
disease outbreaks in wild snake populations if conditions are 
favorable; however no observations have been made in the field, and we 
found no other data that propose a direct linkage between Bd and snake 
mortality.
The Effects of Bullfrogs on Native Aquatic Communities
    Bullfrogs are generally considered one of the most serious threats 
to northern Mexican gartersnakes throughout their range (Conant 1974, 
pp. 471, 487-489; Rosen and Schwalbe 1988, pp. 28-30; Rosen et al. 
2001, pp. 21-22). Bullfrogs have and do threaten some populations of 
narrow-headed gartersnakes, but differing habitat preferences between 
the two temper their effect on narrow-headed gartersnakes. Bullfrogs 
adversely affect northern Mexican and narrow-headed gartersnakes 
through direct predation of juveniles and sub-adults. Bullfrogs also 
compete with northern Mexican gartersnakes. Bullfrogs are not native to 
the southwestern United States or Mexico, and first appeared in Arizona 
in 1926, as a result of a systematic introduction effort by the State 
Game Department (now, the AGFD) for the purposes of sport hunting and 
as a food source (Tellman 2002, p. 43). We are not certain when 
bullfrogs were first reported from New Mexico but presume it was many 
decades ago. Bullfrogs are extremely prolific, are strong colonizers, 
and may disperse distances of up to 10 mi (16 km) across uplands, and 
likely further within drainages (Bautista 2002, p. 131; Rosen and 
Schwalbe 2002a, p. 7; Casper and Hendricks 2005, p. 582; Suhre 2008, 
pers. comm.).
    Bullfrogs are large-bodied, voracious, opportunistic, even 
cannibalistic predators that readily attempt to consume any living 
thing smaller than them. Bullfrogs have a highly varied diet, which has 
been documented to include vegetation, invertebrates, fish, birds, 
mammals, amphibians, and reptiles, including numerous species of snakes 
(eight genera, including six different species of gartersnakes, two 
species of rattlesnakes, and Sonoran gophersnakes (Pituophis catenifer 
affinis)) (Bury and Whelan 1984, p. 5; Clarkson and DeVos 1986, p. 45; 
Holm and Lowe 1995, pp. 37-38; Carpenter et al. 2002, p. 130; King et 
al. 2002; Hovey and Bergen 2003, pp. 360-361; Casper and Hendricks 
2005, pp. 543-544; Combs et al. 2005, p. 439; Wilcox 2005, p. 306; 
DaSilva et al. 2007, p. 443; Neils and Bugbee 2007, p. 443; Rowe and 
Garcia 2012, pp. 633-634). In one study, three different species of 
gartersnakes (Thamnophis sirtalis, T. elegans, and T. ordinoides) 
totaling 11 snakes were found inside the stomachs of resident bullfrogs 
from a single region (Jancowski and Orchard 2013, p. 26). Bullfrogs can 
significantly reduce or eliminate the native amphibian populations 
(Moyle 1973, pp. 18-22; Conant 1974, pp. 471, 487-489; Hayes and 
Jennings 1986, pp. 491-492; Rosen and Schwalbe 1988, pp. 28-30; 2002b, 
pp. 232-238; Rosen et al. 1995, pp. 257-258; 2001, pp. 2, Appendix I; 
Wu et al. 2005, p. 668; Pearl et al. 2004, p. 18; Kupferberg 1994, p. 
95; Kupferburg 1997, pp. 1736-1751; Lawler et al. 1999; Bury and Whelan 
1986, pp. 9-10; Hayes and Jennings 1986, pp. 500-501; Jones and Timmons 
2010, pp. 473-474), which are vital for northern Mexican gartersnakes. 
Different age classes of bullfrogs within a community can affect native 
ranid populations via different mechanisms. Juvenile bullfrogs affect 
native ranids through competition, male bullfrogs affect native ranids 
through predation, and female bullfrogs affect native ranids through 
both mechanisms depending on body size and microhabitat (Wu et al. 
2005, p. 668). Pearl et al. (2004, p. 18) also suggested that the 
effect of bullfrog introductions on native ranids may be different 
based

[[Page 41517]]

on specific habitat conditions, but also suggested that an individual 
ranid frog species' physical ability to escape influences the effect of 
bullfrogs on each native ranid community.
    Bullfrogs have been documented throughout the State of Arizona. 
Holycross et al. (2006, pp. 13-14, 52-61) found bullfrogs at 55 percent 
of sample sites in the Agua Fria subbasin, 62 percent of sites in the 
Verde River subbasin, 25 percent of sites in the Salt River subbasin, 
and 22 percent of sites in the Gila River subbasin. In total, bullfrogs 
were observed at 22 of the 57 sites surveyed (39 percent) across the 
Mogollon Rim (Holycross et al. 2006, p. 13). A number of authors have 
also documented the presence of bullfrogs through their survey efforts 
throughout many subbasins in Arizona and New Mexico adjacent to the 
historical distribution of the northern Mexican or narrow-headed 
gartersnake, including northern Arizona (Sredl et al. 1995a, p. 7; 
1995c, p. 7), central Arizona and along the Mogollon Rim of Arizona and 
New Mexico (Nickerson and Mays 1970, p. 495; Hulse 1973, p. 278; Sredl 
et al. 1995b, p. 9; Drost and Nowak 1997, p. 11; Nowak and Spille 2001, 
p. 11; Holycross et al. 2006, pp. 15-51; Wallace et al. 2008; pp. 243-
244; Helleckson 2012a, pers. comm.), southern Arizona (Rosen and 
Schwalbe 1988, Appendix I; 1995, p. 452; 1996, pp. 1-3; 1997, p. 1; 
2002b, pp. 223-227; 2002c, pp. 31, 70; Holm and Lowe 1995, pp. 27-35; 
Rosen et al. 1995, p. 254; 1996a, pp. 16-17; 1996b, pp. 8-9; 2001, 
Appendix I; Turner et al. 1999, p. 11; Sredl et al. 2000, p. 10; Turner 
2007; p. 41), and along the Colorado River (Vitt and Ohmart 1978, p. 
44; Clarkson and DeVos 1986, pp. 42-49; Ohmart et al. 1988, p. 143). In 
one of the more conspicuous examples, bullfrogs were identified as the 
primary cause for collapse of both the northern Mexican gartersnake and 
its prey base on the SBNWR (Rosen and Schwalbe 1988, p. 28; 1995, p. 
452; 1996, pp. 1-3; 1997, p. 1; 2002b, pp. 223-227; 2002c, pp. 31, 70; 
Rosen et al. 1996b, pp. 8-9).
    Perhaps one of the most serious consequences of bullfrog 
introductions is their persistence in an area once they have become 
established, and the subsequent difficulty in eliminating bullfrog 
populations. Rosen and Schwalbe (1995, p. 452) experimented with 
bullfrog removal at various sites on the SBNWR, in addition to a 
control site with no bullfrog removal in similar habitat on the Buenos 
Aires National Wildlife Refuge (BANWR). Removal of adult bullfrogs, 
without removal of eggs and tadpoles, resulted in a substantial 
increase in younger age-class bullfrogs where removal efforts were the 
most intensive (Rosen and Schwalbe 1997, p. 6). Contradictory to the 
goals of bullfrog eradication, evidence from dissection samples from 
young adult and sub-adult bullfrogs indicated these age-classes readily 
prey upon juvenile bullfrogs (up to the average adult leopard frog 
size) as well as juvenile gartersnakes, which suggests that the 
selective removal of only the large adult bullfrogs (presumed to be the 
most dangerous size class to leopard frogs and gartersnakes), favoring 
the young adult and sub-adult age classes, could indirectly lead to 
increased predation of leopard frogs and juvenile gartersnakes (Rosen 
and Schwalbe 1997, p. 6). These findings illustrate that in addition to 
large adults, subadult bullfrogs also negatively impact northern 
Mexican gartersnakes and their prey species. It also indicates the 
importance of including egg mass and tadpole removal during efforts to 
control bullfrogs and timing removal projects to ensure reproductive 
bullfrogs are removed prior to breeding. Some success in regional 
bullfrog eradication has been had in a few cases described below in the 
section entitled ``Current Conservation of Northern Mexican and Narrow-
headed Gartersnakes.''
    Bullfrogs not only compete with the northern Mexican gartersnake 
for prey items but directly prey upon juvenile and occasionally sub-
adult northern Mexican and narrow-headed gartersnakes (Rosen and 
Schwalbe 1988, pp. 28-31; 1995, p. 452; 2002b, pp. 223-227; Holm and 
Lowe 1995, pp. 29-29; Rossman et al. 1996, p. 177; AGFD In Prep., p. 
12; 2001, p. 3; Rosen et al. 2001, pp. 10, 21-22; Carpenter et al. 
2002, p. 130; Wallace 2002, p. 116). A well-circulated photograph of an 
adult bullfrog in the process of consuming a northern Mexican 
gartersnake at Parker Canyon Lake, Cochise County, Arizona, taken by 
John Carr of the Arizona Game and Fish Department in 1964, provides 
photographic documentation of bullfrog predation (Rosen and Schwalbe 
1988, p. 29; 1995, p. 452). The most recent, physical evidence of 
bullfrog predation of northern Mexican gartersnakes is provided in 
photographs of a dissected bullfrog at Pasture 9 Tank in the San Rafael 
Valley of Arizona that had a freshly-eaten neonatal northern Mexican 
gartersnake in its stomach (Akins 2012, pers. comm.).
    A common observation in northern Mexican gartersnake populations 
that co-occur with bullfrogs is a preponderance of large, mature adult 
snakes with conspicuously low numbers of individuals in the newborn and 
juvenile age size classes due to bullfrogs more effectively preying on 
young small snakes, which ultimately leads to low reproductive rates 
and survival of young (Rosen and Schwalbe 1988, p. 18; Holm and Lowe 
1995, p. 34). In lotic (flowing water) systems, bullfrogs prefer sites 
with low or limited flow, such as backwaters, side channels, and pool 
habitat. These areas are also used frequently by northern Mexican and 
narrow-headed gartersnakes, which likely results in increased predation 
rates and likely depressed recruitment of gartersnakes. Potential 
recruitment problems for northern Mexican gartersnakes due to effects 
from nonnative species are suspected at Tonto Creek (Wallace et al. 
2008, pp. 243-244). Rosen and Schwalbe (1988, p. 18) stated that the 
low recruitment at the SBNWR, a typical characteristic of gartersnake 
populations affected by harmful nonnative species, is the likely cause 
of that populations' decline and possibly for declines in populations 
throughout their range in Arizona. Specific localities within the 
distribution of northern Mexican and narrow-headed gartersnakes where 
bullfrogs have been detected are presented in Appendix A (available at 
http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071).
The Effects of Crayfish on Native Aquatic Communities
    Crayfish are a nonnative species in Arizona and New Mexico and are 
a primary threat to many prey species of northern Mexican and narrow-
headed gartersnakes, and may also prey upon juvenile gartersnakes 
themselves (Fernandez and Rosen 1996, p. 25; Voeltz 2002, pp. 87-88; 
USFWS 2007, p. 22). Fernandez and Rosen (1996, p. 3) studied the 
effects of crayfish introductions on two stream communities in Arizona, 
a low-elevation semi-desert stream and a high mountain stream, and 
concluded that crayfish can noticeably reduce species diversity and 
destabilize food chains in riparian and aquatic ecosystems through 
their effect on vegetative structure, stream substrate (stream bottom; 
i.e., silt, sand, cobble, boulder) composition, and predation on eggs, 
larval, and adult forms of native invertebrate and vertebrate species. 
Crayfish fed on embryos, tadpoles, newly metamorphosed frogs, and adult 
leopard frogs, but they did not feed on egg masses (Fernandez and Rosen 
1996, p. 25). However, Gamradt and Kats (1996, p. 1155) found that 
crayfish readily consumed the egg masses of California newts (Taricha 
torosa). Crayfish are known to also eat fish eggs and larva (Inman et 
al. 1998, p. 17), especially those bound to the substrate (Dorn and

[[Page 41518]]

Mittlebach 2004, p. 2135). Fernandez and Rosen (1996, pp. 6-19, 52-56) 
and Rosen (1987, p. 5) discussed observations of inverse relationships 
between crayfish abundance and native reptile and amphibian 
populations, including narrow-headed gartersnakes, northern leopard 
frogs, and Chiricahua leopard frogs. Crayfish may also affect native 
fish populations. Carpenter (2005, pp. 338-340) documented that 
crayfish may reduce the growth rates of native fish through competition 
for food and noted that the significance of this impact may vary 
between species.
    Crayfish alter the abundance and structure of aquatic vegetation by 
grazing on aquatic and semiaquatic vegetation, which reduces the cover 
needed by frogs and gartersnakes, as well as the food supply for prey 
species such as tadpoles (Fernandez and Rosen 1996, pp. 10-12). 
Fernandez and Rosen (1996, pp. 10-12) found that crayfish frequently 
burrow into stream banks, leading to increased bank erosion, stream 
turbidity, and siltation of stream bottoms. Creed (1994, p. 2098) found 
that filamentous alga (Cladophora glomerata) was at least 10-fold 
greater in aquatic habitats that lacked crayfish. Filamentous alga is 
an important component of aquatic vegetation that provides cover for 
foraging gartersnakes, as well as microhabitat for prey species.
    Crayfish have recently been found to also act as a host for the 
amphibian disease-causing fungus, Bd (McMahon et al. (2013, pp. 210-
213). This could have serious implications for northern Mexican 
gartersnakes because crayfish can now be considered a source of disease 
in habitat that is devoid of amphibians but otherwise potentially 
suitable habitat for immigrating amphibians, such as leopard frogs, 
which could serve as a prey base. Because crayfish are so widespread 
throughout Arizona, New Mexico, and portions of Mexico, this could have 
broad, negative implications for the recovery of native leopard frogs, 
and therefore the recovery of northern Mexican gartersnakes.
    Inman et al. (1998, p. 3) documented crayfish as widely distributed 
and locally abundant in a broad array of natural and artificial free-
flowing and still-water habitats throughout Arizona, many of which 
overlap the historical and current distribution of northern Mexican and 
narrow-headed gartersnakes. Hyatt (undated, p. 71) concluded that the 
majority of waters in Arizona contained at least one species of 
crayfish. In surveying for northern Mexican and narrow-headed 
gartersnakes, Holycross et al. (2006, p. 14) found crayfish in 64 
percent of the sample sites in the Agua Fria subbasin; in 85 percent of 
the sites in the Verde River subbasin; in 46 percent of the sites in 
the Salt River subbasin; and in 67 percent of the sites in the Gila 
River subbasin. In total, crayfish were observed at 35 (61 percent) of 
the 57 sites surveyed across the Mogollon Rim (Holycross et al. 2006, 
p. 14), most of which were sites historically or currently occupied by 
northern Mexican or narrow-headed gartersnakes, or sites the 
investigators believed possessed suitable habitat and may be occupied 
by these gartersnakes based upon the their known historical 
distributions.
    A number of authors have documented the presence of crayfish 
through their survey efforts throughout Arizona and New Mexico in 
specific regional areas, drainages, and lentic wetlands within or 
adjacent to the historical distribution of the northern Mexican or 
narrow-headed gartersnake, including northern Arizona (Sredl et al. 
1995a, p. 7; 1995c, p. 7), central Arizona and along the Mogollon Rim 
of Arizona and New Mexico (Sredl et al. 1995b, p. 9; Fernandez and 
Rosen 1996, pp. 54-55, 71; Inman et al. 1998, Appendix B; Nowak and 
Spille 2001, p. 33; Holycross et al. 2006, pp. 15-51; Brennan 2007, p. 
7; Burger 2008, p. 4; Wallace et al. 2008; pp. 243-244; Brennan and 
Rosen 2009, p. 9; Karam et al. 2009; pp. 2-3; Helleckson 2012a, pers. 
comm.), southern Arizona (Rosen and Schwalbe 1988, Appendix I; Inman et 
al. 1998, Appendix B; Sredl et al. 2000, p. 10; Rosen et al. 2001, 
Appendix I), and along the Colorado River (Ohmart et al. 1988, p. 150; 
Inman et al. 1998, Appendix B). Specific localities within the 
distribution of northern Mexican and narrow-headed gartersnakes where 
crayfish have been detected are presented in Appendix A (available at 
http://www.regulations.gov under Docket No. FWS-R2-ES-2013-0071).
    Like bullfrogs, crayfish can be very difficult, if not impossible, 
to eradicate once they have become established in an area, depending on 
the complexity of the habitat (Rosen and Schwalbe 1996a, pp. 5-8; 
2002a, p. 7; Hyatt undated, pp. 63-71). The use of biological control 
agents such as bacteria, nematodes, and viruses were explored in 
addressing the invasion and persistence of crayfish in the southwestern 
United States, using the organisms' cannibalistic nature as a vector 
(Davidson et al. 2010, pp. 297-310). The use of biological control 
agents tested found them to be ineffective or infeasible in controlling 
crayfish, but a number of other biological pathogens have been 
described in freshwater crayfish that may lend promise to finding an 
appropriate control agent in the future (Davidson et al. 2010, pp. 307-
308). In addition, recent experimentation with ammonia as a piscicide 
indirectly found that crayfish were also effectively eradicated in 
field trials; the first successful and most promising control method 
for this harmful nonnative species in recent times (Ward et al. 2013, 
pp. 402-404). However, it could be potentially several years before 
ammonia is licensed for such use, if ever.
The Effects of Predation-Related Injuries to Gartersnakes
    The tails of gartersnakes are often broken off during predation 
attempts by bullfrogs or crayfish and do not regenerate. The incidence 
of tail breaks in gartersnakes can often be used to assess predation 
pressure within gartersnake populations. Attempted predation occurs on 
both sexes and all ages of gartersnakes within a population, although 
some general trends have been detected. For example, female 
gartersnakes may be more susceptible to predation as evidenced by the 
incidence of tail damage (Willis et al. 1982, pp. 100-101; Rosen and 
Schwalbe1988, p. 22; Mushinsky and Miller 1993, pp. 662-664; Fitch 
2003, p. 212). This can be explained by higher basking rates associated 
with pregnant females that increase their visibility to predators. 
Fitch (2003, p. 212) found that tail injuries in the common gartersnake 
occurred more frequently in adults than in juveniles. Predation on 
juvenile snakes likely results in complete consumption of the animal, 
which would limit observations of tail injury in their age class.
    Tail injuries can have negative effects on the health, longevity, 
and overall success of individual gartersnakes from infection, slower 
swimming and crawling speeds, or impeding reproduction. Mushinsky and 
Miller (1993, pp. 662-664) commented that, while tail breakage in 
gartersnakes can save the life of an individual snake, it also leads to 
permanent handicapping of the snake, resulting in slower swimming and 
crawling speeds, which could leave the snake more vulnerable to 
predation or affect its foraging ability. Willis et al. (1982, p. 98) 
discussed the incidence of tail injury in three species in the genus 
Thamnophis (common gartersnake, Butler's gartersnake (T. butleri), and 
the eastern ribbon snake (T. sauritus)) and concluded that individuals 
that suffered nonfatal injuries prior to reaching a length of 12 in (30 
cm) are not likely to survive and that physiological stress during 
post-injury hibernation may play an important role in subsequent

[[Page 41519]]

mortality. While northern Mexican or narrow-headed gartersnakes may 
survive an individual predation attempt from a bullfrog or crayfish 
with tail damage, secondary effects from infection of the wound may 
significantly contribute to mortality of individuals. Perry-Richardson 
et al. (1990, p. 77) described the importance of tail-tip alignment in 
the successful courtship and mating in Thamnophiine snakes and found 
that missing or shortened tails adversely affected these activities 
and, therefore, mating success. In researching the role of tail length 
in mating success in the red-sided gartersnake (Thamnophis sirtalis 
parietalis), Shine et al. (1999, p. 2150) found that males that 
experienced injuries or the partial or whole loss of the tail 
experienced a three-fold decrease in mating success.
    The frequency of tail injuries can be quite high in a given 
gartersnake population; for example at the SBNWR (Rosen and Schwalbe 
1988, pp. 28-31), 78 percent of northern Mexican gartersnakes had 
broken tails with a ``soft and club-like'' terminus, which suggests 
repeated injury from multiple predation attempts by bullfrogs. While 
medically examining pregnant female northern Mexican gartersnakes, 
Rosen and Schwalbe (1988, p. 28) noted bleeding from the posterior 
region, which suggested to the investigators the snakes suffered from 
``squeeze-type'' injuries inflicted by adult bullfrogs. In another 
example, Holm and Lowe (1995, pp. 33-34) observed tail injuries in 89 
percent of northern Mexican gartersnakes during the early 1990s in 
Scotia Canyon in the Huachuca Mountains, as well as a skewed age class 
ration that favored adults over subadults, which is consistent with 
data collected by Willis et al. (1982, pp. 100-101) on other 
gartersnake species. Bullfrogs are largely thought to be responsible 
for the significant decline of northern Mexican gartersnake and its 
prey base at this locality, although the latter has improved through 
recovery actions. In the Black River, crayfish are very abundant and 
have been identified as the likely cause for a high-frequency of tail 
injuries to narrow-headed gartersnakes (Brennan 2007, p. 7; Brennan and 
Rosen 2009, p. 9). Brennan (2007, p. 5) found that in the Black River, 
14 of 15 narrow-headed gartersnakes captured showed evidence of damaged 
or missing tails (Brennan 2007, p. 5). In 2009, 16 of 19 narrow-headed 
gartersnakes captured in the Black River showed evidence of damaged or 
missing tails (Brennan and Rosen 2009, p. 8). In the upper Verde River 
region, Emmons and Nowak (2013, p. 5) reported that 18 of 49 (37 
percent) northern Mexican gartersnakes captured had scars (n = 17) and/
or missing tails tips (n = 7).
    Vegetation or other forms of protective cover may be particularly 
important for gartersnakes to reduce the effects of harmful nonnative 
species on populations. For example, the population of northern Mexican 
gartersnakes at the Page Springs and Bubbling Ponds State Fish 
Hatcheries occurs with harmful nonnative species (Boyarski 2008b, pp. 
3-4, 8). Yet, only 11 percent of northern Mexican gartersnakes captured 
in 2007 were observed as having some level of tail damage (Boyarski 
2008b, pp. 5, 8). The relatively low occurrence of tail damage, as 
compared to 78 percent of snakes with tail damage found by Rosen and 
Schwalbe (1988, pp. 28-31), may indicate: (1) Adequate vegetation 
density was used by gartersnakes to avoid harmful nonnative species 
predation attempts; (2) a relatively small population of harmful 
nonnative species may be at a comparatively lower density than sites 
sampled by previous studies (harmful nonnative species population 
density data were not collected by Boyarski (2008b)); (3) gartersnakes 
may not have needed to move significant distances at this locality to 
achieve foraging success, which might reduce the potential for 
encounters with harmful nonnative species; or (4) gartersnakes 
infrequently escaped predation attempts by harmful nonnative species, 
were removed from the population, and were consequently not detected by 
surveys.
The Expansion of the American Bullfrog and Crayfish in Mexico
    Bullfrogs have recently been documented as a significant threat to 
native aquatic and riparian species throughout Mexico. Luja and 
Rodr[iacute]guez-Estrella (2008, pp. 17-22) examined the invasion of 
the bullfrog in Mexico. The earliest records of bullfrogs in Mexico 
were Nuevo Leon (1853), Tamaulipas (1898), Morelos (1968), and Sinaloa 
(1969) (Luja and Rodr[iacute]guez-Estrella 2008, p. 20). By 1976, the 
bullfrog was documented in seven more states: Aguacalientes, Baja 
California Sur, Chihuahua, Distrito Federal, Puebla, San Luis Potosi, 
and Sonora (Luja and Rodr[iacute]guez-Estrella 2008, p. 20). The 
bullfrog was recently verified from the state of Hidalgo, Mexico, at an 
elevation of 8,970 feet (2,734 m), which indicates the species 
continues to spread in that country and can exist even at the uppermost 
elevations inhabited by northern Mexican gartersnakes (Duifhuis Rivera 
et al. 2008, p. 479). As of 2008, Luja and Rodr[iacute]guez-Estrella 
(2008, p. 20) have recorded bullfrogs in 20 of the 31 Mexican States 
(65 percent of the states in Mexico) and suspect that they have invaded 
other States, but were unable to find documentation.
    Sponsored by the then Mexican Secretary of Aquaculture Support, 
bullfrogs have been commercially produced for food in Mexico in 
Yucatan, Nayarit, Morelos, Estado de Mexico, Michoac[aacute]n, 
Guadalajara, San Luis Potosi, Tamaulipas, and Sonora (Luja and 
Rodr[iacute]guez-Estrella 2008, p. 20). However, frog legs ultimately 
never gained popularity in Mexican culinary culture (Conant 1974, pp. 
487-489), and Luja and Rodr[iacute]guez-Estrella (2008, p. 22) point 
out that only 10 percent of these farms remain in production. Luja and 
Rodr[iacute]guez-Estrella (2008, pp. 20, 22) document instances where 
bullfrogs have escaped production farms and suspect the majority of the 
frogs that were produced commercially in farms that have since ceased 
operation have assimilated into surrounding habitat.
    Luja and Rodr[iacute]guez-Estrella (2008, p. 20) also state that 
Mexican people deliberately introduce bullfrogs for ornamental 
purposes, or ``for the simple pleasure of having them in ponds.'' The 
act of deliberately releasing bullfrogs into the wild in Mexico was 
cited by Luja and Rodr[iacute]guez-Estrella (2008, p. 21) as being 
``more common than we can imagine.'' Bullfrogs are available for 
purchase at some Mexican pet stores (Luja and Rodr[iacute]guez-Estrella 
2008, p. 22). Luja and Rodr[iacute]guez-Estrella (2008, p. 21) state 
that bullfrog eradication efforts in Mexico are often thwarted by their 
popularity in rural communities (presumably as a food source). 
Currently, no regulation exists in Mexico to address the threat of 
bullfrog invasions or prevent their release into the wild (Luja and 
Rodr[iacute]guez-Estrella 2008, p. 22).
    Rosen and Melendez (2006, p. 54) report bullfrog invasions to be 
prevalent in northwestern Chihuahua and northwestern Sonora, where the 
northern Mexican gartersnake is thought to occur. In many areas, native 
leopard frogs were completely displaced where bullfrogs were observed. 
Rosen and Melendez (2006, p. 54) also demonstrated the relationship 
between fish and amphibian communities in Sonora and western Chihuahua. 
Native leopard frogs, a primary prey item for the northern Mexican 
gartersnake, only occurred in the absence of nonnative fish, and were 
absent from waters containing nonnative species, which included several 
major waters. In Sonora, Rorabaugh (2008a, p. 25) also

[[Page 41520]]

considers the bullfrog to be a significant threat to the northern 
Mexican gartersnake and its prey base, substantiated by field 
observations made during surveys conducted in Chihuahua and Sonora in 
2006 (Rorabaugh 2008b, p. 1).
    Few data were found on the presence or distribution of nonnative 
crayfish species in Mexico. However, in a 2-week gartersnake survey 
effort in 2006 in northern Mexico, crayfish were observed as ``widely 
distributed'' in the valleys of western Chihuahua (Rorabaugh 2008b, p. 
1). Based on the invasive nature of crayfish ecology and their 
distribution in the United States along the Border region, it is 
reasonable to assume that, at a minimum, crayfish are likely 
distributed along the entire Border region of northern Mexico, adjacent 
to where they occur in the United States.
Risks to Gartersnakes From Fisheries Management Activities
    The decline in native fish communities from the effects of harmful 
nonnative fish species has spurred resource managers to take action to 
help recover native fish species. While we fully support activities 
designed to help recover native fish, recovery actions for native fish, 
in the absence of thorough planning, can have significant adverse 
effects on resident gartersnake populations.
    Piscicides--Piscicide is a term that refers to a ``fish poison.'' 
The use of piscicides, such as rotenone or antimycin A, for the removal 
of harmful nonnative fish species has widely been considered invaluable 
for the conservation and recovery of imperiled native fish species 
throughout the United States, and in particular the Gila River basin of 
Arizona and New Mexico (Dawson and Kolar 2003, entire). Antimycin A is 
rarely used anymore, and has been largely replaced by rotenone in field 
applications. Experimentation with ammonia as a piscicide has shown 
promising results and may ultimately replace rotenone in the future as 
a desired control method if legally registered for such use (Ward et 
al. 2013, pp. 402-404). Currently, rotenone is the most commonly used 
piscicide. The active ingredient in rotenone is a natural chemical 
compound extracted from the stems and roots of tropical plants in the 
family Leguminosae that interrupts oxygen absorption in gill-breathing 
animals (Fontenot et al. 1994, pp. 150-151). In the greater Gila River 
subbasin alone, 57 streams or water bodies have been treated with 
piscicide, some on several occasions spanning many years (Carpenter and 
Terrell 2005; Table 6). However, this practice has been the source of 
recent controversy due to a perceived link between rotenone and 
Parkinson's disease in humans, as well as potential effects to 
livestock. Speculation of the potential role of rotenone in Parkinson's 
disease was fueled by Tanner et al. (2011, entire) which correlated the 
incidence of the disease with lifetime exposure to certain pesticides, 
including rotenone. As a result, in 2012, the Arizona State Legislature 
proposed two bills that called for the development of an environmental 
impact statement prior to the application of rotenone or antimycin A 
(S.B. 1453, see State of Arizona Senate (2012b)) and urged the U.S. 
Environmental Protection Agency to deregister rotenone from use in the 
United States (S.B. 1009, see State of Arizona Senate (2012b)). Public 
safety considerations were fully evaluated by a multi-disciplined 
technical team of specialists that found no correlation between 
rotenone applications performed, according to product label 
instructions, and Parkinson's disease (Rotenone Review Advisory 
Committee 2012, pp. 24-25). Nonetheless, continued anxiety regarding 
the use of piscicides for conservation and management of fish 
communities leaves an uncertain future for this invaluable management 
tool. Should circumstances result in the discontinued practice of using 
piscicides for fish recovery and management, the likelihood of recovery 
for listed or sensitive aquatic vertebrates in Arizona, such as 
northern Mexican and narrow-headed gartersnakes, would be substantially 
reduced, if not eliminated outright.
    We are supportive of the use of piscicides and consider the 
practice a vital and scientifically sound tool, the only tool in most 
circumstances, for reestablishing native fish communities and removing 
threats related to nonnative aquatic species in occupied northern 
Mexican and narrow-headed gartersnake habitat. However, it is equally 
important that effects of such treatments to these gartersnakes be 
evaluated during the project planning phase, specifically the amount of 
time a treated water body remains fishless post-treatment. The time 
period between rotenone applications and the subsequent restocking of 
native fish is contingent on two basic variables, the time it takes for 
piscicide levels to reach nontoxic levels and the level of certainty 
required to ensure that renovation goals and objectives have been met 
prior to restocking. Implementation of the latter consideration may 
vary from weeks, to months, to a year or longer, depending on the level 
of certainty required by project proponents. Carpenter and Terrell 
(2005, p. 14) reported that standard protocols, used by the Arizona 
Game and Fish Department for Apache trout renovations, required two 
applications of piscicide before repatriating native fish to a stream, 
waiting a season to see if the renovation was successful, and then 
continuing to renovate if necessary. Another recommendation of past 
protocols included a goal for the renovated water body to remain 
fishless an entire year before restocking (Carpenter and Terrell 2005, 
p. 14). At a minimum and according to our files, reaches of Big Bonito 
Creek, the West Fork Black River, West Fork Gila River, Iron Creek, 
Little Creek, Black Canyon, and O'Donnell Creek have all been subject 
to fish renovations using these or similarly accepted protocols 
(Carpenter and Terrell 2005; Table 6; Paroz and Probst 2009, p. 4; 
Hellekson 2012a, pers. comm.). Therefore, northern Mexican or narrow-
headed gartersnake populations in these streams have likely been 
adversely affected, due to the eradication of a portion of, or their 
entire, prey base in these systems for varying periods of time. Big 
Bonito Creek was restocked with salvaged native fish shortly after 
renovation occurred. However, we are uncertain how long other stream 
reaches remained fishless post-treatment, but presume a minimum of 
weeks in each instance, and possibly a year or longer in some 
instances.
    Future planning in fisheries management has identified several 
streams within the distribution of narrow-headed gartersnakes in New 
Mexico for potential fish barrier construction, for which piscicide 
applications are likely necessary. These streams include Little Creek, 
West Fork Gila River, Middle Fork Gila River, Turkey Creek, Saliz 
Creek, Dry Blue Creek, and the San Francisco River (Riley and Clarkson 
2005, pp. 4-5, 7, 9, 12; Clarkson and Marsh 2012, p. 8; 2013, pp. 1, 4, 
6). Of these, the Middle Fork Gila River and Turkey Creek appear to the 
most likely-chosen for renovation (Clarkson and Marsh 2013, p. 8). Mule 
Creek and Cienega Creek, both occupied by northern Mexican 
gartersnakes, as well as Whitewater Creek (occupied by narrow-headed 
gartersnakes) are under consideration but ultimately may not be chosen 
for renovation for undisclosed reasons (Clarkson and Marsh 2013, pp. 8-
9).
    In addition to fish, rotenone is toxic to amphibians in their gill-
breathing,

[[Page 41521]]

larval life stages; adult forms tend to avoid treated water (Fontenot 
et al. 1994, pp. 151-152). Rotenone has not been found to be directly 
toxic to aquatic snakes, but Fontenot et al. (1994, p. 152) suggested 
that effects from ingesting affected fish, frogs, or tadpoles may 
occur, but have not been adequately researched. The current standard 
operating procedures for piscicide application, as adopted nationally 
and provided in Finlayson et al. (2010, p. 23), provide guidance for 
assuring that non-target, baseline environmental conditions (the biotic 
community) are accounted for in assessing whether mitigation measures 
are necessary. This procedural protocol states, ``Survival and recovery 
of the aquatic community may be demonstrated by sampling plankton, 
macroinvertebrates (aquatic insects, crustacea, leeches, and mollusks), 
and amphibians (frogs, tadpoles, and larval and adult salamanders)'' 
(Finlayson et al. 2010, p. 23). This protocol, adopted by the Arizona 
Game and Fish Department (see AGFD 2012), does not consider the effects 
of leaving a treated water body without a prey base for a sensitive 
species, such as the narrow-headed gartersnake, for extended periods of 
time. In fact, considerations for non-target aquatic reptiles, in 
general, are not mentioned anywhere in this broadly applied piscicide 
application protocol. Consequently, we have no reason to assume that 
effects to either northern Mexican or narrow-headed gartersnake 
populations from the partial or whole-scale removal of their prey base 
have been historically considered in piscicide applications, at least 
through 2006.
    The potentially significant effects to northern Mexican or narrow-
headed gartersnakes described above pertaining to piscicide application 
are largely historical in nature in Arizona, and new methodologies have 
been developed in Arizona to prevent adverse effects to gartersnake 
populations. As of 2012, a new policy was finalized by the Arizona Game 
and Fish Department that includes an early and widespread public 
notification and planning process that involves the approval of several 
decision-makers within four major stages: (1) Piscicide project 
internal review and approval; (2) preliminary planning and public 
involvement; (3) intermediate planning and public involvement; and (4) 
project implementation and evaluation (AGFD 2012, p. 3). Within the 
Internal Review and Approval stage of the process, sensitive, endemic, 
and listed species potentially impacted by the project must be 
identified (AGFD 2012, p. 13), such as northern Mexican or narrow-
headed gartersnakes. In addition, the Arizona Game and Fish Department, 
through their Conservation and Mitigation Program developed as part of 
their sport fish stocking program through 2021, has committed to 
quickly restocking renovated streams that are occupied by either 
northern Mexican or narrow-headed gartersnakes (USFWS 2011, Appendix 
C).
    Although significant efforts are generally made to salvage as many 
native fish as possible prior to treatment, logistics of holding fish 
for several weeks prior to restocking limit the number of individuals 
that can be held safely. Therefore, not every individual fish is 
salvaged, and native fish remaining in the stream are subsequently lost 
during the treatment. The number of fish subsequently restocked is, 
therefore, smaller than the number of fish that were present prior to 
the treatment. The full restoration of native fish populations to pre-
treatment levels may take several years, depending on the size of the 
treated area and the size and maturity of the founding populations. 
Restocking salvaged fish in the fall may allow natural spawning and 
recruitment to begin in the spring, which would provide a more 
immediate benefit to resident gartersnake populations. With regard to 
New Mexico and Mexico, we are uncertain what measures have been 
considered in the past, or implemented currently, to prevent 
significant adverse impacts to northern Mexican or narrow-headed 
gartersnakes from piscicide applications.
    Mechanical Methods--In addition to chemical renovation techniques, 
mechanical methods using electroshocking equipment are often used in 
fisheries management, both for nonnative aquatic species removal and 
fisheries survey and monitoring activities that often occur in 
conjunction with piscicide treatments. Northern Mexican and narrow-
headed gartersnakes often flee into the water as a first line of 
defense when startled. In occupied habitat, gartersnakes present within 
the water are often temporarily paralyzed from electrical impulses 
intended for fish, and are, therefore, readily detected by surveyors 
(Hellekson 2012a, pers. comm.). We are not aware of any research that 
has investigated potential short- or long-term consequences of such 
electrocutions to gartersnakes. In addition to the occupied streams 
noted above that have received piscicide applications (and therefore 
received electroshock surveys), Hellekson (2012, pers. comm.) reported 
narrow-headed gartersnakes being detected via electroshocking in the 
mainstem Gila River from Cliff Dwellings to Little Creek, the East Fork 
Gila River, Little Creek, Black Canyon, the Tularosa River, and Dry 
Blue Creek. Pettinger and Yori (2011, p. 11) reported detecting two 
narrow-headed gartersnakes as a result of electroshocking in the West 
Fork Gila River. Thus, electroshock surveys may be a source of 
additional data related to the occurrence and distribution of both 
northern Mexican and narrow-headed gartersnakes.
    Trapping methods are also used in fisheries surveys, for other 
applications in aquatic species management, and for the collection of 
live baitfish in recreational fishing. One such common method to study 
aquatic or semi-aquatic wildlife (including populations of aquatic 
snakes such as gartersnakes) is through the use of self-baiting wire 
minnow traps. When used to monitor gartersnake populations, wire minnow 
traps are anchored to vegetation, logs, etc., along the shoreline (in 
most applications) and positioned so that half to one-third of the 
trap, along its lateral line, is above water surface to allow snakes to 
surface for air. These traps are then checked according to a 
predetermined schedule. Because the wire, twine, etc., used to anchor 
these traps is fixed in length, these traps may become fully submerged 
if there is a sudden, unanticipated rise in water levels (e.g., storm 
event). During the monsoon in Arizona and New Mexico, these types of 
storm events are common and river hydrographs respond accordingly with 
rapid and dynamic increases in flow. We are aware of examples where 
northern Mexican gartersnakes, intentionally captured in minnow traps, 
have drowned as a direct result of a rapid, unexpected rise in water 
levels. Some examples include an adult female northern Mexican 
gartersnake along lower Tonto Creek in 2004, and an adult and two 
neonates at the Bubbling Springs Hatchery in 2009 and 2010, 
respectively (Holycross et al. 2006, p. 41, Boyarski 2011, pp. 2-3). In 
another example, involving an underwater funnel trap used to survey for 
lowland leopard frogs, a large adult female northern Mexican 
gartersnake was discovered deceased in the trap (T. Jones 2012a, pers. 
comm.). Death of that individual was likely due to drowning or 
predation by numerous crayfish that were also confined in the funnel 
trap with the gartersnake (T. Jones 2012a, pers. comm.). There are 
likely additional cases where northern Mexican or narrow-headed 
gartersnake

[[Page 41522]]

mortality from trapping have not been reported, where trapping has 
occurred in occupied habitat prone to flash flooding.
    Minnow traps are often deployed for monitoring fully aquatic 
species, such as fish, and are, therefore, intentionally positioned in 
the water column where they are fully under water. Traps used for this 
purpose may be checked less frequently, because risks to fully aquatic 
species are less if held in the trap for longer periods of time. As 
fish collectively become trapped, the trap becomes incidentally self-
baited for gartersnakes and, if deployed in habitat occupied by either 
northern Mexican or narrow-headed gartersnakes, these traps may 
accidentally attract, capture, and drown gartersnakes that are actively 
foraging under water and are lured to the traps because of captured 
prey species. Neonatal northern Mexican and narrow-headed gartersnakes 
can also wriggle through the mesh of some wire minnow traps and become 
lodged halfway through, depending on the pore size of the wire mesh 
(Jaeger 2012, pers. comm.). If not found in time, this situation would 
likely result in their death from drowning, predation, or exposure.
    The use of minnow traps is also allowed in recreational fishing in 
Arizona and New Mexico (AGFD 2013, p. 57; NMDGF 2013, p. 17). In 
Arizona and New Mexico, it is lawful to set minnow traps for the 
collection of live baitfish (AGFD 2013, pp. 56-57; NMDGF 2013, p. 17). 
In Arizona, minnow traps used for collecting live baitfish must be 
checked once daily (AGFD 2013, pp. 56-57); in New Mexico, there is no 
stipulation on time intervals in the regulations to check minnow traps 
(NMDGF 2013, p. 17). In either scenario in either state, these minnow 
traps are likely to be fully submerged when in use and pose a drowning 
hazard to resident gartersnakes while foraging underwater, as they can 
be lured into the traps by fish already caught.
    The extent to which trapping-related mortality can affect northern 
Mexican or narrow-headed gartersnake populations is uncertain, but 
there is reason for concern if adult females are lost from populations 
where recruitment appears low or nonexistent, especially in low-density 
populations. While we are less certain about northern Mexican or 
narrow-headed gartersnake mortality from trapping efforts intended for 
other species, we assume such events have historically been unreported, 
but also acknowledge that the percentage of snakes intentionally caught 
in minnow traps that actually drown is likely to be comparatively low. 
We also note that the aquatic community data generated from field 
research using these traps are critical to our understanding of 
northern Mexican and narrow-headed gartersnake ecology, population 
trends, and responses to threats on the landscape, and we believe that 
better communication and coordination among programs with regard to 
gartersnake concerns can help.
    Intentional Dewatering--Lastly, dewatering or water fluctuation 
techniques are sometimes considered for eliminating undesirable fish 
species from water bodies (Finlayson et al. 2010, p. 4). Dewatering of 
occupied northern Mexican or narrow-headed gartersnake habitat would 
have obvious deleterious effects to affected populations by removing a 
primary habitat feature and eliminating the prey base. Depending on the 
availability of suitable habitat regionally and the length of time 
water is absent, these activities may ultimately cause local 
extirpations of gartersnake populations. Because northern Mexican 
gartersnakes often occupy lentic water bodies or intermittently watered 
canyon bottoms, where this practice is most feasible, effects of 
dewatering activities may disproportionately affect that species. This 
technique is being considered by the AGFD for pools within Redrock 
Canyon where northern Mexican gartersnakes could be adversely affected; 
however it is expected that northern Mexican gartersnakes are being 
considered by the AGFD in their implementation planning process.
Summary
    In our review of the scientific and commercial literature, we have 
found that over time, native aquatic communities, specifically the 
native prey bases for northern Mexican and narrow-headed gartersnakes, 
have been significantly weakened to the point of near collapse as a 
result of the cumulative effects of disease and harmful nonnative 
species such as bullfrogs, crayfish, and spiny-rayed fish. Harmful 
nonnative species have been intentionally introduced or have naturally 
moved into virtually every subbasin throughout the distribution of 
northern Mexican and narrow-headed gartersnakes in the United States 
and Mexico. According to Geographic Information System GIS analyses, 
nonnative, spiny-rayed fish are known to occur in 90 percent of the 
historical distribution of the northern Mexican gartersnake and 85 
percent of the historical distribution of the narrow-headed gartersnake 
in the United States. Bullfrogs are known to occur in 85 percent of the 
historical distribution of the northern Mexican gartersnake and 53 
percent of the historical distribution of the narrow-headed gartersnake 
in the United States. Crayfish are known to occur in 77 percent of the 
historical distribution of the northern Mexican gartersnake and 75 
percent of the historical distribution of the narrow-headed gartersnake 
in the United States. Nonnative, spiny-rayed fish, bullfrogs, and 
crayfish are known to occur simultaneously in 65 percent of the 
historical distribution of the northern Mexican gartersnake and 44 
percent of the historical distribution of the narrow-headed gartersnake 
in the United States.
    Native fish are important prey for northern Mexican gartersnakes 
but much more so for narrow-headed gartersnakes. Predation by and 
competition with primarily nonnative, spiny-rayed fish species, and 
secondarily with crayfish, are widely considered to be the primary 
reason for major declines in native fish communities throughout the 
range of both gartersnakes. This fundamental premise is captured by the 
fact that in Arizona, 19 of 31 (61 percent) of all native fish species 
are listed under the Act. Consequently, Arizona ranks the highest of 
all 50 States in the percentage of native fish species with declining 
trends (85.7 percent). Similar trends in the loss of native fish 
biodiversity have been described in New Mexico and Mexico. Native 
amphibians such as the Chiricahua leopard frog, an important component 
of the northern Mexican gartersnake prey base, have declined 
significantly and may face future declines as a result of Bd and 
harmful nonnative species. We cite numerous examples where historical 
native frog populations have been wholly replaced by harmful nonnative 
species, both on local and regional scales. These declines have 
directly contributed to subsequent northern Mexican gartersnake 
population declines or extirpations in these areas. Collectively, the 
literature confirms that an adequate native prey base is essential to 
the conservation and recovery of northern Mexican gartersnakes, and 
that this native ranid frog prey base may face an uncertain future if 
harmful nonnative species continue to persist and expand their 
distributions in occupied habitat.
    We have found that the best available commercial and scientific 
information supports the fact that harmful nonnative species are the 
single most important threat to northern Mexican and narrow-headed 
gartersnakes and their prey bases, and therefore have had a profound 
role in their decline. A large body of literature documents that

[[Page 41523]]

northern Mexican and narrow-headed gartersnakes are uniquely 
susceptible to the influence of harmful nonnative species in their 
biotic communities. This sensitivity is largely the result of complex 
ecological interactions that result in direct predation on 
gartersnakes; shifts in biotic community structure from largely native 
to largely nonnative; and competition for a diminished prey base that 
can ultimately result in the injury, starvation, or death of northern 
Mexican or narrow-headed gartersnakes followed by reduced recruitment, 
population declines, and extirpations.
    Lastly, we found that fisheries management activities can have 
significant negative effects on resident gartersnake populations when 
gartersnakes are not considered in project planning and implementation. 
We fully support the continued use of rotenone and other fisheries 
management techniques in the conservation and recovery of native fish. 
However, we also acknowledge the potential and significant threat 
rotenone use may pose to these gartersnakes if their habitat is left 
with a fish community that is dangerously depleted or entirely removed 
for extended periods of time. New policies and mitigation measures have 
been developed in Arizona that will reduce the likelihood of these 
activities having significant effects on either northern Mexican or 
narrow-headed gartersnake populations. However, some level of effect 
should still be expected, based on logistical complications and 
complexities of restoring fish populations to pre-treatment levels. We 
expect to coordinate with resource managers in New Mexico as we do in 
Arizona, to ensure gartersnake populations are not significantly 
affected by these activities. Other mechanisms or activities used in 
fisheries management, such as electroshocking, trapping, or dewatering, 
can result in the injury or death of northern Mexican or narrow-headed 
gartersnakes, where these activities coincide with extant populations, 
and if they have not been considered in the planning or implementation 
processes. The significance of these losses depends on the status of 
the gartersnake population affected. We found no evidence to conclude 
that fisheries management techniques threaten the northern Mexican 
gartersnake in Mexico.
    On the most basic level, the presence of harmful nonnative species 
ultimately affects where northern Mexican and narrow-headed 
gartersnakes can live as viable populations. Collectively, the 
ubiquitous presence of harmful nonnative species across the landscape 
has appreciably reduced the quantity of suitable gartersnake habitat 
and changed its spatial orientation on the landscape. Most northern 
Mexican and narrow-headed gartersnake populations, even some considered 
viable today, live in the presence of harmful nonnative species. While 
they continue to persist, they do so under constant stress from 
unnatural levels of predation and competition associated with harmful 
nonnative species. This weakens their resistance to other threats, 
including those that affect the physical suitability of their habitat 
(discussed below). This ultimately renders populations much less 
resilient to stochastic, natural, or anthropogenic stressors that could 
otherwise be withstood. Over time and space, subsequent population 
declines have threatened the genetic representation of each species 
because many populations have become disconnected and isolated from 
neighboring populations. Expanding distances between extant populations 
coupled with increasing populations of harmful nonnative species 
prevents normal colonizing mechanisms that would otherwise reestablish 
populations where they have become extirpated. This subsequently leads 
to a reduction in species redundancy when isolated, small populations 
are at increased vulnerability to the effects of stochastic events, 
without a means for natural recolonization. Ultimately, the effect of 
scattered, small, and disjunct populations, without the means to 
naturally recolonize, is weakened species resiliency as a whole, which 
ultimately enhances the risk of either or both species becoming 
endangered. Therefore, based on the best available scientific and 
commercial information, we conclude that harmful nonnative species are 
the most significant threat to both the northern Mexican and narrow-
headed gartersnake, rangewide, now and in the foreseeable future.

Main Factors That Destroy or Modify the Physical Habitat of Northern 
Mexican and Narrow-Headed Gartersnakes

The Relationship Between Harmful Nonnative Species and Adverse Effects 
to Physical Habitat
    As discussed at length above, we found harmful nonnative species to 
be a significant and widespread factor that continues to drive further 
declines in and extirpations of gartersnake populations. Also in our 
review of the literature, we found various threats have affected, and 
continue to affect, primary components of the physical habitat required 
by northern Mexican and narrow-headed gartersnakes. These activities 
result in the loss of stream flow, and include examples such as dams, 
water diversions, groundwater pumping, and development. Researchers 
agree that the period from 1850 to 1940 marked the greatest loss and 
degradation of riparian and aquatic communities in Arizona, many of 
which were caused by anthropogenic (human-caused) land uses and the 
primary and secondary effects of those uses (Stromberg et al. 1996, p. 
114; Webb and Leake 2005, pp. 305-310). An estimated one-third of 
Arizona's pre-settlement wetlands has dried or been rendered 
ecologically dysfunctional (Yuhas 1996, entire). However, not all 
aquatic and riparian habitats in the United States that support 
northern Mexican or narrow-headed gartersnakes have been significantly 
degraded or lost. Despite the loss or modification of aquatic and 
riparian habitat we describe below, large reaches of the Verde, Salt, 
San Pedro, and Gila Rivers, as well as several of their tributaries, 
remain functionally suitable as physical habitat for either gartersnake 
species. When we use the term ``physical habitat,'' we refer to the 
structural integrity of aquatic and terrestrial components to habitat, 
such as plant species richness, density, available water, and any 
feature of habitat that does not pertain to the animal community. The 
animal community (the prey and predator species that co-occur within 
habitat) is not considered in our usage of ``physical habitat,'' for 
reasons described immediately below.
    Our treatment of how various threats may affect the northern 
Mexican or narrow-headed gartersnake is based, in part, on recent 
observations made in Mexico that illustrate the relationship of 
gartersnakes' physical habitat suitability to the presence of native 
prey species and the lack of harmful nonnative species (predators on or 
competitors with the northern Mexican gartersnake and narrow-headed 
gartersnake), and the presence, or lack thereof, of attributes 
associated with these gartersnakes' physical habitat. In 2007, two 
groups consisting of agency biologists (including U.S. Fish and 
Wildlife Service staff), species experts, and field technicians 
conducted numerous gartersnake surveys in Durango and Chihuahua, Mexico 
(Burger 2007, p. 1). In the state of Durango, 19 survey sites provided 
observation records for 144 gartersnakes, representing five different 
species, including the northern Mexican gartersnake (Burger et al. 
2010, p. 13). In

[[Page 41524]]

the state of Chihuahua, 12 survey sites provided observation records 
for 50 gartersnakes, representing two species, including the northern 
Mexican gartersnake (Burger et al. 2010, p. 13). A main reason for this 
survey trip was to collect genetic samples from the subspecies 
described, at that time, under Thamnophis rufipunctatus, chiefly T. r. 
unilabialis and T. r. nigronuchalis. The genetic samples collected 
ultimately provided the evidence for the current taxonomic status of 
the narrow-headed gartersnake proposed by Wood et al. (2011, entire).
    While considerable gartersnake habitat in Mexico is affected by the 
presence of harmful nonnative species (Conant 1974, pp. 471, 487-489; 
Contreras Balderas and Lozano 1994, pp. 383-384; Unmack and Fagan 2004, 
p. 233; Miller et al. 2005, pp. 60-61; Rosen and Melendez 2006, p. 54; 
Luja and Rodr[iacute]guez-Estrella 2008, pp. 17-22), Burger (2007, pp. 
1-72) surveyed several sites in remote areas that appeared to be free 
of nonnative species. In some sites, the physical habitat for northern 
Mexican gartersnakes and similar species of gartersnakes appeared to be 
in largely good condition, but few or no gartersnakes were detected. At 
other sites, the physical habitat was drastically affected by 
overgrazing, rural development, or road crossings; however, 
gartersnakes were relatively easily detected, which indicated that 
population densities were adequate. It should be noted that we do not 
have the necessary data to calculate population trends at sampled 
localities. Riparian and aquatic habitats in Arizona and New Mexico are 
in relatively better physical condition compared to observations of 
these habitats made in Durango and Chihuahua, Mexico. However, 
nonnative species are also ubiquitous in these same habitats across the 
landscape in the southwestern United States, based on our literature 
review and GIS modeling. Several sites visited by Burger (2007, pp. 1-
72) in Durango and Chihuahua, Mexico, had physical habitat in poor to 
very poor condition, but were largely free of nonnative species. These 
situations are rarely encountered in Arizona and New Mexico and, 
therefore, provided Burger (2007, pp. 1-72) a unique opportunity to 
examine differences in gartersnake population densities based on 
condition of the physical habitat, without the confounding effect of 
nonnative species on resident gartersnake populations.
    Burger (2007, pp. 6, 12, 36, 41, 58, 63) detected moderate to high 
densities of gartersnakes at six sites where their physical habitat was 
moderately to highly impacted by land uses, but were largely free of 
nonnatives. Burger (2007, pp. 18, 26, 32, 61, 64, 66, 67, 69, 72) also 
detected either low densities or no gartersnakes at nine sites where 
the physical habitat was in moderate to good condition, but where 
nonnative species were detected. Eight streams surveyed by Burger 
(2007, pp. 15, 22, 46, 49, 51-52, 54, 62) were largely dewatered and 
without fish, and had few to no gartersnake observations. One site 
presented an anomaly, 19 northern Mexican gartersnakes and two T. 
unilabialis were observed at Rio Papigochic at Temosachic, where 
crayfish were noted as abundant, but no other nonnatives were detected 
(Burger 2007, p. 67). The disproportionate number of northern Mexican 
gartersnakes detected, as compared to the more aquatic T. unilabialis, 
may be due to differences in habitat preference, or the potential 
disproportionate effect of crayfish on T. unilabialis because of their 
more aquatic behavior. Similar data were not collected from the 
remaining seven sites, which prevents further evaluation of these sites 
in these contexts.
    Our observations of gartersnake populations in Mexico provide 
evidence for the relative importance of native prey species and the 
lack of nonnative species in comparison to the physical attributes of 
gartersnake habitat. As a result, we have formulated three general 
hypotheses: (1) Northern Mexican and narrow-headed gartersnakes may be 
more resilient to adverse effects to physical habitat in the absence of 
harmful nonnative species, and therefore, more sensitive to adverse 
effects to physical habitat in the presence of harmful nonnative 
species; (2) the presence of an adequate prey base is important for 
persistence of gartersnake populations regardless of whether or not 
harmful nonnative species are present; and (3) detections and effects 
from harmful nonnative species appear to decrease from north to south 
in the Mexican states of Chihuahua and Durango (from the United States-
Mexico International Border), as discussed in Unmack and Fagan (2004, 
pp. 233-243).
    Based on field data collected by Burger (2007, entire) and on the 
above hypotheses, we evaluated the significance of effects to physical 
habitat in the context of the presence or absence of nonnative species. 
Effects to the physical habitat of gartersnakes can have varying 
effects on the gartersnakes themselves depending on the composition of 
their biotic community. In the presence of harmful nonnative species, 
effects to physical habitat that negatively affect the prey base for 
northern Mexican or narrow-headed gartersnakes are believed to be 
comparatively more significant than those that do not. As previously 
discussed, harmful nonnative species are largely ubiquitous throughout 
the range of northern Mexican and narrow-headed gartersnakes and 
therefore exacerbate the effects from threats to their physical 
habitat.
Altering or Dewatering Aquatic Habitat
    Dams and Diversions--The presence of water is critical for northern 
Mexican and narrow-headed gartersnakes, as well as their prey base. Of 
all the activities that may threaten their physical habitat, none are 
more serious than those that reduce flows or dewater habitat, such as 
dams, diversions, flood-control projects, and groundwater pumping. Such 
activities are widespread in Arizona. For example, municipal water use 
in central Arizona increased by 39 percent from 1998 to 2006 (American 
Rivers 2006), and at least 35 percent of Arizona's perennial rivers 
have been dewatered, assisted by approximately 95 dams that are in 
operation in Arizona today (Turner and List 2007, pp. 3, 9). Larger 
dams may prevent movement of fish between populations (which affects 
prey availability for northern Mexican and narrow-headed gartersnakes) 
and dramatically alter the flow regime of streams through the 
impoundment of water (Ligon et al. 1995, pp. 184-189). These diversions 
also require periodic maintenance and reconstruction, resulting in 
potential habitat damages and inputs of sediment into the active 
stream.
    Flow regimes within stream systems are a primary factor that shape 
fish community assemblages. The timing, duration, intensity, and 
frequency of flood events has been altered to varying degrees by the 
presence of dams, which has an effect on fish communities. 
Specifically, Haney et al. (2008, p. 61) suggested that flood pulses 
may help to reduce populations of nonnative species and efforts to 
increase the baseflows may assist in sustaining native prey species for 
northern Mexican and narrow-headed gartersnakes. However, the 
investigators in this study also suggest that, because the northern 
Mexican gartersnake preys on both fish and frogs, it may be less 
affected by reductions in baseflow of streams (Haney et al. 2008, pp. 
82, 93). Collier et al. (1996, p. 16) mentions that water development 
projects are one of two main causes of the decline of native fish in 
the Salt and Gila rivers of Arizona. Unregulated flows with elevated 
discharge events favor native species, and regulated flows, absent 
significant

[[Page 41525]]

discharge events, favor nonnative species (Probst et al. 2008, p. 
1246). Interactions among native fish, nonnative fish, and flow regimes 
were observed in the upper reaches of the East Fork of the Gila River. 
Prior to the 1983 and 1984 floods in the Gila River system, native fish 
occurrence was limited, while nonnative fish were moderately common. 
Following the 1983 flood event, adult nonnative predators were 
generally absent, and native fish were subsequently collected in 
moderate numbers in 1985 (Propst et al. 1986, p. 83). These 
relationships are most readily observed in canyon-bound streams, where 
shelter sought by nonnative species during large-scale floods is 
minimal (Probst et al. 2008, p. 1249). Probst et al. (2008, p. 1246) 
also suggested the effect of nonnative fish species on native fish 
communities may be most significant during periods of natural drought 
(simulated by artificial dewatering).
    Effects from flood control projects threaten riparian and aquatic 
habitat, as well as threaten the northern Mexican gartersnake directly 
in lower Tonto Creek. Kimmell (2008, pers. comm.), Gila County Board of 
Supervisors (2008, pers. comm.), Trammell (2008, pers. comm.), and 
Sanchez (2008, pers. comm.) all discuss a growing concern of residents 
that live within or adjacent to the floodplain of Tonto Creek in Gila 
County, Arizona, both upstream and downstream of the town of Gisela, 
Arizona. Specifically, there is growing concern to address threats to 
private property and associated infrastructure posed by flooding of 
Tonto Creek (Sanchez 2008, pers. comm.). An important remaining 
population of northern Mexican gartersnakes within the large Salt River 
subbasin occurs on Tonto Creek. In Resolution No. 08-06-02, the Gila 
County Board of Supervisors proactively declared a state of emergency 
within Gila County as a result of the expectation for heavy rain and 
snowfall causing repetitive flooding conditions (Gila County Board of 
Supervisors 2008, pers. comm.). In response, the Arizona Division of 
Emergency Management called meetings and initiated discussions among 
stakeholders in an attempt to mitigate these flooding concerns (Kimmell 
2008, pers. comm., Trammell 2008, pers. comm.).
    Mitigation measures that have been discussed include removal of 
riparian vegetation, removal of debris piles, potential channelization 
of Tonto Creek, improvements to existing flood control structures or 
addition of new structures, and the construction of new bridges. 
Adverse effects from these types of activities to aquatic and riparian 
habitat, and to the northern Mexican gartersnake or its prey species, 
will result from the physical alteration or destruction of habitat, 
significant increases to flow velocity, and removal of key foraging 
habitat and areas to hibernate, such as debris jams. Specifically, 
flood control projects permanently alter stream flow characteristics 
and have the potential to make the stream unsuitable as habitat for the 
northern Mexican gartersnake by reducing or eliminating stream 
sinuosity and associated pool and backwater habitats that are critical 
to northern Mexican gartersnakes and their prey species. Threats 
presented by these flood control planning efforts are considered 
imminent.
    Many streams in New Mexico, currently or formerly occupied by 
northern Mexican or narrow-headed gartersnakes, have been or could be 
affected by water withdrawals. Approximately 9.5 river mi (15.3 km) of 
the Gila River mainstem in New Mexico, from Little Creek to the Gila 
Bird Area, are in private ownership and have been channelized, and the 
water is largely used for agricultural purposes (Hellekson 2012a, pers. 
comm.). In addition, the Hooker Dam has been proposed in the reach 
above Mogollon Creek and below Turkey Creek as part of the Central 
Arizona Project, but remains in deferment status (Hellekson 2012a, 
pers. comm.). If constructed, Hooker Dam would significantly alter or 
reduce stream flow; favor nonnative, spiny-rayed fish species; and 
likely render the affected reach unsuitable for narrow-headed 
gartersnakes. Below the Gila Bird Area, but above the Middle Box of the 
mainstem Gila River, several water diversions have reduced stream flow 
(Hellekson 2012a, pers. comm.). Channelization has also affected a 
privately owned reach of Whitewater Creek from the Catwalk downstream 
to Glenwood, New Mexico (Hellekson 2012a, pers. comm.). The Gila River 
downstream of the town of Cliff, New Mexico, flows through a broad 
valley where irrigated agriculture and livestock grazing are the 
predominant uses. Human settlement has increased since 1988 (Propst et 
al. 2008, pp. 1237-1238). Agricultural practices have led to dewatering 
of the river in the Cliff-Gila valley at times during the dry season 
(Soles 2003, p. 71). For those portions of the Gila River downstream of 
the Arizona-New Mexico border, agricultural diversions and groundwater 
pumping have caused declines in the water table, and surface flows in 
the central portion of the river basin are diverted for agriculture 
(Leopold 1997, pp. 63-64; Tellman et al. 1997, pp. 101-104).
    The San Francisco River in New Mexico has undergone sedimentation, 
riparian habitat degradation, and extensive water diversion, and at 
present has an undependable water supply throughout portions of its 
length. The San Francisco River is seasonally dry in the Alma Valley, 
and two diversion structures fragment habitat in the upper Alma Valley 
and at Pleasanton (NMDGF 2006, p. 302). An approximate 2-stream-mi 
(3.2-km) reach of the lower San Francisco River between the Glenwood 
Diversion and Alma Bridge, which would otherwise be good narrow-headed 
gartersnake habitat, has been completely dewatered by upstream 
diversions (Hellekson 2012a, pers. comm.).
    Additional withdrawals of water from the Gila and San Francisco 
Rivers may occur in the future (McKinnon 2006d). Implementation of 
Title II of the Arizona Water Settlements Act (AWSA) (Pub. L. 108-451) 
would facilitate the exchange of Central Arizona Project water within 
and between southwestern river basins in Arizona and New Mexico, and 
may result in the construction of new water development projects. 
Section 212 of the AWSA pertains to the New Mexico Unit of the Central 
Arizona Project. The AWSA provides for New Mexico water users to 
deplete 140,000 acre-feet of additional water from the Gila Basin in 
any 10-year period. The settlement also provides the ability to divert 
that water without complaint from downstream pre-1968 water rights in 
Arizona. New Mexico will receive $66 million to $128 million in non-
reimbursable federal funding. The Interstate Stream Commission (ISC) 
funds may be used to cover costs of an actual water supply project, 
planning, environmental mitigation, or restoration activities 
associated with or necessary for the project, and may be used on one or 
more of 21 alternative projects ranging from Gila National Forest San 
Francisco River Diversion/Ditch improvements to a regional water supply 
project (the Deming Diversion Project). At this time, it is not known 
how the funds will be spent, or which potential alternative(s) may be 
chosen. While multiple potential project proposals have been accepted 
by the New Mexico Office of the State Engineer (NMOSE) (NMOSE 2011a, p. 
1), implementation of the AWSA is still in the planning stages on these 
streams, and final notice is expected by the end of 2014. Should water 
be diverted from the Gila or San Francisco Rivers, flows would be 
diminished and direct and indirect losses and degradation of

[[Page 41526]]

habitat for the narrow-headed gartersnake and its prey species would 
result.
    In addition to affecting the natural behavior of streams and rivers 
through changes in timing, intensity, and duration of flood events, 
dams create reservoirs that alter resident fish communities. Water 
level fluctuation can affect the degree of benefit to harmful nonnative 
fish species. Reservoirs that experience limited or slow fluctuations 
in water levels are especially beneficial to harmful nonnative species 
whereas reservoirs that experience greater fluctuations in water levels 
provide less benefit for harmful nonnative species. The timing of 
fluctuating water levels contributes to their effect; a precipitous 
drop in water levels during harmful nonnative fish reproduction is most 
deleterious to their recruitment. A drop in water levels outside of the 
reproductive season of harmful nonnative species has less effect on 
overall population dynamics.
    The cross-sectional profile of any given reservoir also contributes 
to its benefit for harmful nonnative fish species. Shallow reservoir 
profiles generally provide maximum space and elevated water 
temperatures favorable to reproduction of harmful nonnative species, 
and deep reservoir profiles with limited shallow areas provide 
commensurately less benefit. Examples of reservoirs that benefit 
harmful nonnative species, and therefore adversely affect northern 
Mexican and narrow-headed gartersnakes (presently or historically), 
include Horseshoe and Bartlett Reservoirs on the Verde River, the San 
Carlos Reservoir on the Gila River, and Roosevelt, Saguaro, Canyon, and 
Apache Lakes on the Salt River. The Salt River Project (SRP) operates 
the previously mentioned reservoirs on the Verde and Salt Rivers and, 
in the case of Horseshoe and Bartlett Reservoirs, received section 
10(a)(1)(B) take authorization under the Act for adverse effects to 
several avian and aquatic species (including northern Mexican and 
narrow-headed gartersnakes) through a comprehensive threat minimization 
and mitigation program found in SRP's habitat conservation plan (SRP 
2008, entire). There is no such minimization and mitigation program 
developed for the operation Lake Roosevelt, where limited fluctuation 
in reservoir levels benefit harmful nonnative species and negatively 
affect northern Mexican or narrow-headed gartersnakes and their prey 
bases in Tonto Creek and the upper Salt River. A detailed analysis of 
the effects of reservoir operations on aquatic communities is provided 
in our intra-Service biological and conference opinion provided in 
USFWS (2008, pp. 112-131).
    The Effect of Population Growth and Development on Water Demands 
and Gartersnake Habitat--Arizona's population is expected to double 
from 5 million to 10 million people by the year 2030, which will put 
increasing pressure on water demands (Overpeck 2008). Arizona increased 
its population by 474 percent from 1960 to 2006 (Gammage 2008, p. 15), 
and is second only to Nevada as the fastest growing State in terms of 
human population (Social Science Data Analysis Network (SSDAR) 2000, 
p.1). Over approximately the same time period, population growth rates 
in Arizona counties where northern Mexican or narrow-headed gartersnake 
habitat exists have varied by county but are no less remarkable, and 
all are increasing: Maricopa (463 percent); Pima (318 percent); Santa 
Cruz (355 percent); Cochise (214 percent); Yavapai (579 percent); Gila 
(199 percent); Graham (238 percent); Apache (228 percent); Navajo (257 
percent); Yuma (346 percent); LaPaz (142 percent); and Mohave (2,004 
percent) (SSDAR 2000). From 1960 to 2006, the Phoenix metropolitan area 
alone grew by 608 percent, and the Tucson metropolitan area grew by 356 
percent (Gammage 2008, p. 15). Population growth in Arizona is expected 
to be focused along wide swaths of land from the international border 
in Nogales, through Tucson, Phoenix, and north into Yavapai County 
(called the Sun Corridor ``Megapolitan''), and is predicted to have 8 
million people by 2030, an 82.5 percent increase from 2000 (Gammage et 
al. 2008, pp. 15, 22-23). If build-out occurs as expected, it could 
indirectly affect (through increased recreation pressure and demand for 
water) currently occupied habitat for the northern Mexican or narrow-
headed gartersnake, particularly regional populations in Red Rock 
Canyon in extreme south-central Arizona, lower Cienega Creek near Vail, 
Arizona, and the Verde Valley.
    The effect of the increased water withdrawals may be exacerbated by 
the current, long-term drought facing the arid southwestern United 
States. Philips and Thomas (2005, pp. 1-4) provided stream flow records 
that indicate that the drought Arizona experienced between 1999 and 
2004 was the worst drought since the early 1940s and possibly earlier. 
The Arizona Drought Preparedness Plan Monitoring Technical Committee 
(ADPPMTC) (2012) determined the drought status within the Arizona 
distributions of northern Mexican and narrow-headed gartersnakes, 
through June 2012, to be in ``severe drought.'' Ongoing drought 
conditions have depleted recharge of aquifers and decreased base flows 
in the region. While drought periods have been relatively numerous in 
the arid Southwest from the mid-1800s to the present, the effects of 
human-caused impacts on riparian and aquatic communities have 
compromised the ability of these communities to function under the 
additional stress of prolonged drought conditions. We further discuss 
the effect of climate change-induced drought below.
    The Arizona Department of Water Resources (ADWR) manages water 
supplies in Arizona and has established five Active Management Areas 
(AMAs) across the State (ADWR 2006, entire). An AMA is established by 
ADWR when an area's water demand has exceeded the groundwater supply 
and an overdraft has occurred. In these areas, groundwater use has 
exceeded the rate where precipitation can recharge the aquifer. 
Geographically, these five AMAs overlap the historical distribution of 
the northern Mexican or narrow-headed gartersnake, or both, in Arizona. 
The establishment of these AMAs further illustrates the condition of 
and future threats to riparian habitat in these areas and are a cause 
of concern for the long-term maintenance of northern Mexican and 
narrow-headed gartersnake habitat. Such overdrafts reduce surface water 
flow of streams that are hydrologically connected to the aquifer, and 
these overdrafts can be further exacerbated by surface water 
diversions, placing further stress on the aquifer. The presence of 
water is a primary habitat component for northern Mexican and narrow-
headed gartersnakes. Existing water laws in Arizona and New Mexico are 
inadequate to protect gartersnake habitat from the dewatering effects 
of groundwater withdrawals. New Mexico water law does not include 
provisions for instream water rights to protect fish and wildlife and 
their habitats. Arizona water law does recognize such provisions; 
however, because this change is relatively recent, instream water 
rights have low priority, and are often never fulfilled because more 
senior diversion rights have priority. Gelt (2008, pp. 1-12) 
highlighted the fact that existing water laws are outdated and reflect 
a legislative interpretation of the resource that is not consistent 
with current scientific understanding, such as the important connection 
between groundwater and surface water.
    Water for development and urbanization is often supplied by

[[Page 41527]]

groundwater pumping and surface water diversions from sources that 
include reservoirs and Central Arizona Project's allocations from the 
Colorado River. The hydrologic connection between groundwater and 
surface flow of intermittent and perennial streams is becoming better 
understood. Groundwater pumping creates a cone of depression within the 
affected aquifer that slowly radiates outward from the well site. When 
the cone of depression intersects the hyporheic zone of a stream (the 
active transition zone between two adjacent ecological communities 
under or beside a stream channel or floodplain between the surface 
water and groundwater that contributes water to the stream itself), the 
surface water flow may decrease, and the subsequent drying of riparian 
and wetland vegetative communities can follow. Continued groundwater 
pumping at such levels draws down the aquifer sufficiently to create a 
water-level gradient away from the stream and floodplain (Webb and 
Leake 2005, p. 309). Finally, complete disconnection of the aquifer and 
the stream results in strong negative effects to riparian vegetation 
(Webb and Leake 2005, p. 309). The hyporheic zone can promote ``hot 
spots'' of productivity where groundwater upwelling produces nitrates 
that can enhance the growth of vegetation, but its significance is 
contingent upon its activity and extent of connection with the 
groundwater (Boulton et al. 1998, p. 67; Boulton and Hancock 2006, pp. 
135, 138). If complete disconnection occurs, the hyporheic zone could 
be adversely affected. Such ``hot spots'' can enhance the quality of 
northern Mexican and narrow-headed gartersnake habitat. Conversely, 
changes to the duration and timing of upwelling can potentially lead to 
localized extinctions in biota (Boulton and Hancock 2006, p. 139), 
reducing or eliminating gartersnake habitat suitability.
    The arid southwestern United States is characterized by limited 
annual precipitation, which means limited annual recharge of 
groundwater aquifers; even modest changes in groundwater levels from 
groundwater pumping can affect above-ground stream flow as evidenced by 
depleted flows in the Santa Cruz, Verde, San Pedro, Blue, and lower 
Gila rivers as a result of regional groundwater demands (Fernandez and 
Rosen 1996, p. 70; Stromberg et al. 1996, pp. 113, 124-128; Rinne et 
al. 1998, p. 9; Voeltz 2002, pp. 45-47, 69-71; Haney et al. 2009 p. 1). 
Demands are expected to exceed flows in Arivaca Creek, Babocomari 
River, lower Cienega Creek, San Pedro River, upper Verde River, and 
Agua Fria River (Haney et al. 2009 p. 3, Table 2), which historically 
or currently support northern Mexican or narrow-headed gartersnake 
populations. The complete loss of surface flow would result in local or 
regional extirpations of both species, or limit the species' recovery 
in these areas.
    Water depletion is a concern for the Verde River (American Rivers 
2006; McKinnon 2006a). Barnett and Hawkins (2002, Table 4) reported 
population census data from 1970, as well as projections for 2030, for 
communities situation along the middle Verde River or within the Verde 
River subbasin as a whole, such as Clarkdale, Cottonwood, Jerome, and 
Sedona. From 1970-2000, population growth was recorded as Clarkdale 
(384 percent), Cottonwood (352 percent), Jerome (113 percent), and 
Sedona (504 percent) (Barnett and Hawkins 2002, Table 4). Projected 
growth in these same communities from 1970-2030 was tabulated at 
Clarkdale (620 percent), Cottonwood (730 percent), Jerome (292 
percent), and Sedona (818 percent) (Barnett and Hawkins 2002, Table 4). 
These examples of documented and projected population growth within the 
Verde River subbasin indicate ever-increasing water demands that have 
impacted base flow in the Verde River and are expected to continue. The 
middle and lower Verde River has limited or no flow during portions of 
the year due to agricultural diversion and upstream impoundments, and 
has several impoundments in its middle reaches, which could expand the 
area of impacted northern Mexican and narrow-headed gartersnake 
habitat. Blasch et al. (2006, p. 2) suggests that groundwater storage 
in the Verde River subbasin has already declined due to groundwater 
pumping and reductions in natural channel recharge resulting from 
stream flow diversions.
    Also impacting water in the Verde River, the City of Prescott, 
Arizona, experienced a 22 percent increase in population between 2000 
and 2005 (U.S. Census Bureau 2010, p. 1), averaging around 4 percent 
growth per year (City of Prescott 2010, p. 1). In addition, the towns 
of Prescott Valley and Chino Valley experienced growth rates of 66 and 
67 percent, respectively (Arizona Department of Commerce 2009a, p. 1; 
2009b, p. 1). This growth is facilitated by groundwater pumping in the 
Verde River basin. In 2004, the cities of Prescott and Prescott Valley 
purchased a ranch in the Big Chino basin in the headwaters of the Verde 
River, with the intent of drilling new wells to supply up to 
approximately 4,933,927 cubic meters (4,000 acre-feet (AF)) of 
groundwater per year. If such drilling occurs, it could have serious 
adverse effects on the mainstem and tributaries of the Verde River.
    Scientific studies have shown a link between the Big Chino aquifer 
and spring flows that form the headwaters of the Verde River. It is 
estimated that 80 to 86 percent of baseflow in the upper Verde River 
comes from the Big Chino aquifer (Wirt 2005, p. G8). However, while 
these withdrawals could potentially dewater the upper 26 mi (42 km) of 
the Verde River (Wirt and Hjalmarson 2000, p. 4; Marder 2009, pp. 188-
189), it is uncertain that this project will occur given the legal and 
administrative challenges it faces; however, an agreement in principle 
was signed between various factions associated with water rights and 
interests on the Verde River (Citizens Water Advocacy Group 2010; Verde 
Independent 2010, p. 1). An indepth discussion of the effects to Verde 
River from pumping of the Big Chino Aquifer is available in Marder 
(2009, pp. 183-189). Within the Verde River subbasin, and particularly 
within the Verde Valley, where the northern Mexican and narrow-headed 
gartersnakes could occur, several other activities continue to threaten 
surface flows (Rinne et al. 1998, p. 9; Paradzick et al. 2006, pp. 104-
110). Many tributaries of the Verde River are permanently or seasonally 
dewatered by water diversions for agriculture (Paradzick et al. 2006, 
pp. 104-110). The demands for surface water allocations from rapidly 
growing communities and agricultural and mining interests have altered 
flows or dewatered significant reaches during the spring and summer 
months in some of the Verde River's larger, formerly perennial 
tributaries such as Wet Beaver Creek, West Clear Creek, and the East 
Verde River (Girmendonk and Young 1993, pp. 45-47; Sullivan and 
Richardson 1993, pp. 38-39; Paradzick et al. 2006, pp. 104-110), which 
may have supported either the northern Mexican or narrow-headed 
gartersnake, or both. Groundwater pumping in the Tonto Creek drainage 
regularly eliminates surface flows during parts of the year (Abarca and 
Weedman 1993, p. 2).
    Further south in Arizona, portions of the San Pedro River are now 
classified as formerly perennial (The Nature Conservancy 2006), and 
water withdrawals are a concern for the San Pedro River. The Cananea 
Mine in Sonora, Mexico, owns the land surrounding the headwaters of the 
San Pedro. There is disagreement on the

[[Page 41528]]

exact amount of water withdrawn by the mine, Mexicana de Cananea, which 
is one of the largest open-pit copper mines in the world. However, 
there is agreement that it is the largest water user in the basin 
(Harris et al. 2001; Varady et al. 2000, p. 232). Along the upper San 
Pedro River, Stromberg et al. (1996, pp. 124-127) found that wetland 
herbaceous species, important as cover for northern Mexican 
gartersnakes, are the most sensitive to the effects of a declining 
groundwater level. Webb and Leake (2005, pp. 302, 318-320) described a 
correlative trend regarding vegetation along southwestern streams from 
historically being dominated by marshy grasslands preferable to 
northern Mexican gartersnakes, to currently being dominated by woody 
species that are more tolerant of declining water tables due to their 
deeper rooting depths.
    Another primary groundwater user in the San Pedro subbasin is Fort 
Huachuca. Fort Huachuca is a U.S. Army installation located near Sierra 
Vista, Arizona. Initially established in 1877 as a camp for the 
military, the water rights of the Fort are predated only by those of 
local Indian tribes (Varady et al. 2000, p. 230). Fort Huachuca has 
pursued a rigorous water use reduction plan, working over the past 
decade to reduce groundwater consumption in the Sierra Vista subbasin. 
Their efforts have focused primarily on reductions in groundwater 
demand both on-post and off-post and increased artificial and enhanced 
recharge of the groundwater system. Annual pumping from Fort Huachuca 
production wells has decreased from a high of approximately 3,200 acre-
feet (AF) in 1989, to a low of approximately 1,400 AF in 2005. In 
addition, Fort Huachuca and the City of Sierra Vista have increased the 
amount of water recharged to the regional aquifer through construction 
of effluent recharge facilities and detention basins that not only 
increase stormwater recharge, but mitigate the negative effects of 
increased runoff from urbanization. The amount of effluent that was 
recharged by Fort Huachuca and the City of Sierra Vista in 2005 was 426 
AF and 1,868 AF, respectively. During this same year, enhanced 
stormwater recharge at detention basins was estimated to be 129 AF. The 
total net effect of all the combined efforts initiated by Fort Huachuca 
has been to reduce the net groundwater consumption by approximately 
2,272 AF (71 percent) since 1989 (USFWS 2007, pp. 41-42).
    Groundwater withdrawal in Eagle Creek, primarily for water 
supplying the large open-pit copper mine at Morenci, Arizona, dries 
portions of the stream (Sublette et al. 1990, p. 19; USFWS 2005; Propst 
et al. 1986, p. 7) that otherwise supports habitat for narrow-headed 
gartersnakes. Mining is the largest industrial water user in 
southeastern Arizona. The Morenci mine on Eagle Creek is North 
America's largest producer of copper, covering approximately 24,281 
hectares (ha) (60,000 acres (ac)). Water for the mine is imported from 
the Black River, diverted from Eagle Creek as surface flows, or 
withdrawn from the Upper Eagle Creek Well Field (Arizona Department of 
Water Resources 2009, p. 1).
    The Rosemont Copper Mine proposed to be constructed in the north-
eastern area of the Santa Rita Mountains in Santa Cruz County, Arizona, 
will include a mine pit that will be excavated to a depth greater than 
that of the regional aquifer. Water will thus drain from storage in the 
aquifer into the pit. The need to dewater the pit during mining 
operations will thus result in ongoing removal of aquifer water 
storage. Upon cessation of mining, a pit lake will form, and 
evaporation from this water body will continue to remove water from 
storage in the regional aquifer. This aquifer also supplies baseflow to 
Cienega Creek, immediately east of the proposed project site. Several 
groundwater models have been developed to analyze potential effects of 
expected groundwater withdrawals. However, the latest independent 
models did not indicate that significant effects to baseflows in 
Cienega Creek are expected from the Rosemont Copper Mine into the 
foreseeable future.
    The best available scientific and commercial information indicates 
that, regardless of the scenario, any reduction in the presence or 
availability of water is a significant threat to northern Mexican and 
narrow-headed gartersnakes, their prey base, and their habitat. This is 
because water is a fundamental need that supports the necessary aquatic 
and riparian habitats and prey species needed by both species of 
gartersnake. Through GIS analyses, we found that approximately 32 
percent of formerly perennial streams have been dewatered within the 
historical distribution of the northern Mexican gartersnake. Within the 
historical distribution of the narrow-headed gartersnake, approximately 
13 percent of formerly perennial streams have been dewatered.
    Climate Change and Drought--Our analyses under the Act include 
consideration of ongoing and projected changes in climate. The terms 
``climate'' and ``climate change'' are defined by the Intergovernmental 
Panel on Climate Change (IPCC). ``Climate'' refers to the mean and 
variability of different types of weather conditions over time, with 30 
years being a typical period for such measurements, although shorter or 
longer periods also may be used (IPCC 2007, p. 78). The term ``climate 
change'' thus refers to a change in the mean or variability of one or 
more measures of climate (e.g., temperature or precipitation) that 
persists for an extended period, typically decades or longer, whether 
the change is due to natural variability, human activity, or both (IPCC 
2007, p. 78). Various types of changes in climate can have direct or 
indirect effects on species. These effects may be positive, neutral, or 
negative and they may change over time, depending on the species and 
other relevant considerations, such as the effects of interactions of 
climate with other variables (e.g., habitat fragmentation) (IPCC 2007, 
pp. 8-14, 18-19). In our analyses, we use our expert judgment to weigh 
relevant information, including uncertainty, in our consideration of 
various aspects of climate change and their predicted effects on 
northern Mexican and narrow-headed gartersnakes.
    The ecology and natural histories of northern Mexican and narrow-
headed gartersnakes are strongly linked to water. As discussed above, 
the northern Mexican gartersnake is a highly aquatic species and relies 
largely upon other aquatic species, such as ranid frogs and native and 
nonnative, soft-rayed fish as prey. The narrow-headed gartersnake is 
the most aquatic of the southwestern gartersnakes and is a specialized 
predator on native and nonnative, soft-rayed fish found primarily in 
clear, rocky, higher elevation streams. Because of their aquatic 
nature, Wood et al. (2011, p. 3) predict they may be uniquely 
susceptible to environmental change, especially factors associated with 
climate change. Together, these factors are likely to make northern 
Mexican and narrow-headed gartersnakes vulnerable to effects of climate 
change and drought discussed below.
    Several climate-related trends have been detected since the 1970s 
in the southwestern United States including increases in surface 
temperatures, rainfall intensity, drought, heat waves, extreme high 
temperatures, average low temperatures (Overpeck 2008, entire). Annual 
precipitation amounts in the southwestern United States may decrease by 
10 percent by the year 2100 (Overpeck 2008, entire). Seager et al. 
(2007, pp. 1181-1184) analyzed 19

[[Page 41529]]

different computer models of differing variables to estimate the future 
climatology of the southwestern United States and northern Mexico in 
response to predictions of changing climatic patterns. All but 1 of the 
19 models predicted a drying trend within the Southwest; one predicted 
a trend toward a wetter climate (Seager et al. 2007, p. 1181). A total 
of 49 projections were created using the 19 models, and all but 3 
predicted a shift to increasing aridity (dryness) in the Southwest as 
early as 2021-2040 (Seager et al. 2007, p. 1181). Northern Mexican and 
particularly narrow-headed gartersnakes, and their prey bases, depend 
on permanent or nearly permanent water for survival. A large percentage 
of habitats within the current distribution of northern Mexican and 
narrow-headed gartersnakes are predicted to be at risk of becoming more 
arid with reductions in snow pack levels (Seager et al. 2007, pp. 1183-
1184). This has severe implications for the integrity of aquatic and 
riparian ecosystems and the water that supports them. In assessing 
potential effects of predicted climate change to river systems in New 
Mexico, Molles (2007) found that: (1) Variation in stream flow will 
likely be higher than variation in precipitation; (2) predicted effects 
such as warming and drying are expected to result in higher variability 
in stream flows; and (3) high-elevation fish and non-flying 
invertebrates (which are prey for gartersnake prey species) are at 
greatest risk from effects of predicted climate change. Enquist and 
Gori (2008, p. iii) found that most of New Mexico's mid- to high-
elevation forests and woodlands have experienced either consistently 
warmer and drier conditions or greater variability in temperature and 
precipitation from 1991 to 2005. However, Enquist et al. (2008, p. v) 
found the upper Gila and San Francisco subbasins, which support narrow-
headed gartersnake populations, have experienced very little change in 
moisture stress during the same period.
    Cavazos and Arriaga (2010, entire) found that average temperatures 
along the Mexican Plateau in Mexico could rise by as much as 
1.8[emsp14][deg]F (1 [deg]C) in the next 20 years and by as much as 
9[emsp14][deg]F (5 [deg]C) in the next 20 years, according to their 
models. Cavazos and Arriaga (2010, entire) also found that 
precipitation may decrease up to 12 percent over the next 20 years in 
the same region, with pronounced decreases in winter and spring 
precipitation.
    Potential drought associated with changing climatic patterns may 
adversely affect the amphibian prey base for the northern Mexican 
gartersnake. Amphibians may be among the first vertebrates to exhibit 
broad-scale changes in response to changes in global climatic patters 
due to their sensitivity to changes in moisture and temperature (Reaser 
and Blaustein 2005, p. 61). Changes in temperature and moisture, 
combined with the ongoing threat to amphibians from the persistence of 
disease causing bacteria such as Batrachochytrium dendrobatidis (Bd) 
may cause prey species to experience increased physiological stress and 
decreased immune system function, possibly leading to disease outbreaks 
(Carey and Alexander 2003, pp. 111-121; Pounds et al. 2006, pp. 161-
167). Of the 30 different vertebrate species in the Sky Island region 
of southeastern Arizona, the northern Mexican gartersnake was found to 
be the fifth-most vulnerable (total combined score) to predicted 
climate change; one of its primary prey species, the Chiricahua leopard 
frog, was determined to be the fourth most vulnerable (Coe et al. 2012, 
p. 16). Both the northern Mexican gartersnake and the Chiricahua 
leopard frog ranked the highest of all species assessed for 
vulnerability of their habitat to predicted climate change, and the 
Chiricahua leopard frog was also found to be the most vulnerable in 
terms of its physiology (Coe et al. 2012, p. 18). Relative uncertainty 
for the vulnerability assessment provided by Coe et al. (2012, Table 
2.2) ranged from 0 to 8 (higher score means greater uncertainty), and 
the northern Mexican gartersnake score was 3, meaning that the 
vulnerability assessment was more certain than not. Coe et al. (2012, 
entire) focused their assessment of species vulnerability to climate 
change on those occurring on the Coronado National Forest in 
southeastern Arizona. However, it is not unreasonable to hypothesize 
that results might be applicable in a larger, regional context as 
applied in most climate models.
    The bullfrog, also assessed by Coe et al. (2012, pp. 16, 18, Table 
2.2), was shown to be significantly less vulnerable to predicted 
climate change than either northern Mexican gartersnakes or Chiricahua 
leopard frogs with an uncertainty score of 1 (very certain). We suspect 
bullfrogs were found to be less vulnerable by Coe et al. (2012) to 
predicted climate change in southeastern Arizona due to their dispersal 
and colonization capabilities, capacity for self-sustaining 
cannibalistic populations, and ecological dominance where they occur. 
Based upon climate change models, nonnative species biology, and 
ecological observations, Rahel et al. (2008, p. 551) concluded that 
climate change could foster the expansion of nonnative aquatic species 
into new areas, magnify the effects of existing aquatic nonnative 
species where they currently occur, increase nonnative predation rates, 
and heighten the virulence of disease outbreaks in North America.
    Rahel and Olden (2008, p. 526) expect that increases in water 
temperatures in drier climates such as the southwestern United States 
will result in periods of prolonged low flows and stream drying. These 
effects from changing climatic conditions may have profound effects on 
the amount, permanency, and quality of habitat for northern Mexican and 
narrow-headed gartersnakes as well as their prey base. Changes in 
amount or type of winter precipitation may affect snowpack levels as 
well as the timing of their discharge into high-elevation streams. Low 
or no snowpack levels would jeopardize the amount and reliability of 
stream flow during the arid spring and early summer months, which would 
increase water temperatures to unsuitable levels or eliminate flow 
altogether. Harmful nonnative species such as largemouth bass are 
expected to benefit from prolonged periods of low flow (Rahel and Olden 
2008, p. 527). These nonnative predatory species evolved in river 
systems with hydrographs that were largely stable, not punctuated by 
flood pulses in which native species evolved and benefit from. Probst 
et al. (2008, p. 1246) also suggested that nonnative fish species may 
benefit from drought.
    Changes to climatic patterns may warm water temperatures, alter 
stream flow events, and increase demand for water storage and 
conveyance systems (Rahel and Olden 2008, pp. 521-522). Warmer water 
temperatures across temperate regions are predicted to expand the 
distribution of existing harmful nonnative species, which evolved in 
warmer water temperatures, by providing 31 percent more suitable 
habitat. This conclusion is based upon studies that compared the 
thermal tolerances of 57 fish species with predictions made from 
climate change temperature models (Mohseni et al. 2003, p. 389). Eaton 
and Scheller (1996, p. 1,111) reported that while several cold-water 
fish species (such as trout, a prey species for narrow-headed 
gartersnakes) in North America are expected to have reductions in their 
distribution from effects of climate change, several harmful nonnative 
species are expected to increase their distribution. In the 
southwestern United States, this situation may occur where the quantity 
of water is sufficient to

[[Page 41530]]

sustain effects of potential prolonged drought conditions but where 
water temperature may warm to a level found suitable to harmful 
nonnative species that were previously physiologically precluded from 
occupation of these areas. Species that are particularly harmful to 
northern Mexican and narrow-headed gartersnake populations such as the 
green sunfish, channel catfish, largemouth bass, and bluegill are 
expected to increase their distribution by 7.4 percent, 25.2 percent, 
30.4 percent, and 33.3 percent, respectively (Eaton and Scheller 1996, 
p. 1,111).
    Vanishing Cienegas--Cienegas are particularly important habitat for 
the northern Mexican gartersnake and are considered ideal for the 
species because these areas present ideal habitat characteristics for 
the species and its prey base and have been shown to support robust 
populations of both (Rosen and Schwalbe 1988, p. 14). Hendrickson and 
Minckley (1984, p. 131) defined cienegas as ``mid-elevation (3,281-
6,562 ft (1,000-2000 m)) wetlands characterized by permanently 
saturated, highly organic, reducing [lowering of oxygen level] soils.'' 
Many of these unique communities of the southwestern United States, 
Arizona in particular, and Mexico have been lost in the past century to 
streambed modification, intensive livestock grazing, woodcutting, 
artificial drainage structures, stream flow stabilization by upstream 
dams, channelization, and stream flow reduction from groundwater 
pumping and water diversions (Hendrickson and Minckley 1984, p. 161). 
Stromberg et al. (1996, p. 114) state that cienegas were formerly 
extensive along streams of the Southwest; however, most were destroyed 
during the late 1800s, when groundwater tables declined several meters 
and stream channels became incised.
    Many sub-basins, where cienegas have been severely modified or lost 
entirely, wholly or partially overlap the historical distribution of 
the northern Mexican gartersnake, including the San Simon, Sulphur 
Springs, San Pedro, and Santa Cruz valleys of southeastern and south-
central Arizona. The San Simon Valley in Arizona possessed several 
natural cienegas with abundant vegetation prior to 1885, and was used 
as a watering stop for pioneers, military, and surveying expeditions 
(Hendrickson and Minckley 1984, pp. 139-140). In the subsequent 
decades, the disappearance of grasses and commencement of severe 
erosion were the result of historical grazing pressure by large herds 
of cattle, as well as the effects from wagon trails that paralleled 
arroyos, occasionally crossed them, and often required stream bank 
modification (Hendrickson and Minckley 1984, p. 140). Today, only the 
artificially maintained San Simon Cienega exists in this valley. 
Similar accounts of past conditions, adverse effects from historical 
anthropogenic activities, and subsequent reduction in the extent and 
quality of cienega habitats in the remaining valleys are also provided 
in Hendrickson and Minckley (1984, pp. 138-160).
    Development and Recreation within Riparian Corridors--Development 
within and adjacent to riparian areas has proven to be a significant 
threat to riparian biological communities and their suitability for 
native species (Medina 1990, p. 351). Riparian communities are 
sensitive to even low levels (less than 10 percent) of urban 
development within a subbasin (Wheeler et al. 2005, p. 142). 
Development along or within proximity to riparian zones can alter the 
nature of stream flow dramatically, changing once-perennial streams 
into ephemeral streams, which has direct consequences on the riparian 
community (Medina 1990, pp. 358-359). Medina (1990, pp. 358-359) 
correlated tree density and age class representation to stream flow, 
finding that decreased flow reduced tree densities and generally 
resulted in few to no small-diameter trees. Small- diameter trees 
assist northern Mexican and narrow-headed gartersnakes by providing 
additional habitat complexity, thermoregulatory opportunities, and 
cover needed to reduce predation risk and enhance the usefulness of 
areas for maintaining optimal body temperature. The presence of small 
shrubs and trees may be particularly important for the narrow-headed 
gartersnake (Deganhardt et al. 1996, p. 327). Development within 
occupied riparian habitat also likely increases the number of human-
gartersnake encounters and therefore the frequency of adverse human 
interaction, described below.
    Obvious examples of the influence of urbanization and development 
can be observed within the areas of greater Tucson and Phoenix, 
Arizona, where impacts have modified riparian vegetation, structurally 
altered stream channels, facilitated nonnative species introductions, 
and dewatered large reaches of formerly perennial rivers where the 
northern Mexican gartersnake historically occurred (Santa Cruz, lower 
Gila, and lower Salt Rivers, respectively). Urbanization and 
development of these areas, along with the introduction of nonnative 
species, are largely responsible for the likely extirpation of the 
northern Mexican gartersnake from these regions.
    Development near riparian areas usually leads to increased 
recreation. Riparian areas located near urban areas are vulnerable to 
the effects of increased recreation. An example of such an area within 
the existing distribution of both the northern Mexican and narrow-
headed gartersnake is the Verde Valley. The reach of the Verde River 
that winds through the Verde Valley receives a high amount of 
recreational use from people living in central Arizona (Paradzick et 
al. 2006, pp. 107-108). Increased human use results in the trampling of 
near-shore vegetation, which reduces cover for gartersnakes, especially 
newborns. Increased human visitation in occupied habitat also increases 
the potential for adverse human interactions with gartersnakes, which 
frequently leads to the capture, injury, or death of the snake (Rosen 
and Schwalbe 1988, p. 43; Ernst and Zug 1996, p. 75; Green 1997, pp. 
285-286; Nowak and Santana-Bendix 2002, pp. 37-39).
    Oak Creek Canyon, which represents an important source population 
for narrow-headed gartersnakes, is also a well-known example of an area 
with very high recreation levels. Recreational activities in the 
Southwest are often heavily tied to water bodies and riparian areas, 
due to the general lack of surface water on the landscape. Increased 
recreational impacts on the quantity and quality of water, as well as 
the adjacent vegetation, negatively affect northern Mexican and narrow-
headed gartersnakes. The impacts to riparian habitat from recreation 
can include movement of people or livestock, such as horses or mules, 
along stream banks, trampling, loss of vegetation, and increased danger 
of fire starts (Northern Arizona University 2005, p. 136; Monz et al. 
2010, pp. 553-554). In the arid Gila River Basin, recreational impacts 
are disproportionately distributed along streams as a primary focus for 
recreation (Briggs 1996, p. 36). Within the range of the northern 
Mexican and narrow-headed gartersnakes in the United States, the 
majority of the occupied areas occur on Federal lands, which are 
managed for recreation and other purposes. On the Gila National Forest, 
heavy recreation use within occupied narrow-headed gartersnake habitat 
is thought to impact populations along the Middle Fork Gila River, the 
mainstem Gila River between Cliff Dwellings and Little Creek, and 
Whitewater Creek from the Catwalk to Glenwood (Hellekson 2012a, pers. 
comm.).
    Urbanization on smaller scales can also impact habitat suitability 
and the prey base for the northern Mexican or

[[Page 41531]]

narrow-headed gartersnakes, such as along Tonto Creek, within the Verde 
Valley, and the vicinity of Rock Springs along the Agua Fria River 
(Girmendonk and Young 1997, pp. 45-52; Voeltz 2002, pp. 58-59, 69-71; 
Holycross et al.2006, pp. 53, 56; Paradzick et al. 2006, pp. 89-90). 
One of the most stable populations of the northern Mexican gartersnake 
in the United States, at the Page Springs and Bubbling Ponds fish 
hatcheries along Oak Creek, is threatened by ongoing small-scale 
development projects that may adversely affect the northern Mexican 
gartersnake directly through physical harm or injury or indirectly from 
effects to its habitat or prey base (AGFD 1997a, p. 8; AGFD 1997b, p. 
4). Current and future management and maintenance of Bubbling Ponds 
include a variety of activities that would potentially affect snake 
habitat, such as the maintenance of roads, buildings, fences, and 
equipment, as well as development (residences, storage facilities, 
asphalt, resurfacing, etc.) and both human- and habitat-based 
enhancement projects (AGFD 1997b, pp. 8-9; Wilson and Company 1991, pp. 
1-40; 1992, pp. 1-99). However, we expect adaptive management in 
relation to activities at the hatcheries, as informed by population 
studies that have occurred there, will help reduce the overall effects 
to this critical northern Mexican gartersnake population and avoid 
extirpation of this important population.
    Diminishing Water Quantity and Quality in Mexico--While effects to 
riparian and aquatic communities affect both the northern Mexican 
gartersnake and the narrow-headed gartersnake in the United States, 
Mexico provides habitat only for the northern Mexican gartersnake. 
Threats to northern Mexican gartersnake habitat in Mexico include 
intensive livestock grazing, urbanization and development, water 
diversions and groundwater pumping, loss of vegetation cover and 
deforestation, and erosion, as well as impoundments and dams that have 
modified or destroyed riparian and aquatic communities in areas of 
Mexico where the species occurred historically. Rorabaugh (2008, pp. 
25-26) noted threats to northern Mexican gartersnakes and their native 
amphibian prey base in Sonora, which included disease, pollution, 
intensive livestock grazing, conversion of land for agriculture, 
nonnative plant invasions, and logging. Ramirez Bautista and Arizmendi 
(2004, p. 3) stated that the principal threats to northern Mexican 
gartersnake habitat in Mexico include the drying of wetlands, intensive 
livestock grazing, deforestation, wildfires, and urbanization. In 
addition, nonnative species, such as bullfrogs and nonnative, spiny-
rayed fish, have been introduced throughout Mexico and continue to 
disperse naturally, broadening their distributions (Conant 1974, pp. 
487-489; Miller et al. 2005, pp. 60-61; Luja and Rodr[iacute]guez-
Estrella 2008, pp. 17-22).
    Mexico's water needs for urban and agricultural development, as 
well impacts to aquatic habitat from these uses, are linked to 
significant human population growth over the past century in Mexico. 
Mexico's human population grew 700 percent from 1910 to 2000 (Miller et 
al. 2005, p. 60). Mexico's population increased by 245 percent from 
1950 to 2002, and is projected to grow by another 28 percent by 2025 
(EarthTrends 2005). Growth is concentrated in Mexico's northern states 
(Stoleson et al. 2005, Table 3.1) and is now skewed towards urban areas 
(Miller et al. 2005, p. 60). The human population of Sonora, Mexico, 
doubled in size from 1970 (1.1 million) to 2000 (2.2 million) (Stoleson 
et al. 2005, p. 54). The population of Sonora is expected to increase 
by 23 percent, to 2.7 million people, in 2020 (Stoleson et al. 2005, p. 
54). Increasing trends in Mexico's human population will continue to 
place additional stress on the country's freshwater resources and 
continue to be the catalyst for the elimination of northern Mexican 
gartersnake habitat and prey species.
    Much knowledge of the status of aquatic ecosystems in Mexico has 
come from fisheries research, which is particularly applicable to 
assessing the status of northern Mexican gartersnakes because of the 
gartersnakes' dependency on a functioning prey base. Fisheries research 
is also particularly applicable because of the role fishes serve as 
indicators of the status of the aquatic community as a whole. Miller et 
al. (2005) reported information on threats to freshwater fishes, and 
riparian and aquatic communities in specific water bodies from several 
regions throughout Mexico within the range of the northern Mexican 
gartersnake: the R[iacute]o Grande (dam construction, p. 78 and 
extirpations of freshwater fish species, pp. 82, 112); headwaters of 
the R[iacute]o Lerma (extirpation of freshwater fish species, nonnative 
species, pollution, dewatering, pp. 60, 105, 197); Lago de Chapala and 
its outlet to the R[iacute]o Grande de Santiago (major declines in 
freshwater fish species, p. 106); medium-sized streams throughout the 
Sierra Madre Occidental (localized extirpations, logging, dewatering, 
pp. 109, 177, 247); the R[iacute]o Conchos (extirpations of freshwater 
fish species, p. 112); the r[iacute]os Casas Grandes, Santa 
Mar[iacute]a, del Carmen, and Laguna Bustillos (water diversions, 
groundwater pumping, channelization, flood control practices, 
pollution, and introduction of nonnative species, pp. 124, 197); the 
R[iacute]o Santa Cruz (extirpations, p. 140); the R[iacute]o Yaqui 
(nonnative species, pp. 148, Plate 61); the R[iacute]o Colorado 
(nonnative species, p. 153); the r[iacute]os Fuerte and Culiac[aacute]n 
(logging, p. 177); canals, ponds, lakes in the Valle de M[eacute]xico 
(nonnative species, extirpations, pollution, pp. 197, 281); the 
R[iacute]o Verde Basin (dewatering, nonnative species, extirpations, 
Plate 88); the R[iacute]o Mayo (dewatering, nonnative species, p. 247); 
the R[iacute]o Papaloapan (pollution, p. 252); lagos de Zacapu and 
Yuriria (habitat destruction, p. 282); and the R[iacute]o P[aacute]nuco 
Basin (nonnative species, p. 295).
    Excessive sedimentation also appears to be a significant problem 
for aquatic habitat in Mexico. Recent estimates indicate that 80 
percent of Mexico is affected by soil erosion caused by vegetation 
removal related to grazing, fires, agriculture, deforestation, etc. The 
most serious erosion is occurring in the states of Guanajuato (43 
percent of the state's land area), Jalisco (25 percent of the state's 
land area), and M[eacute]xico (25 percent of the state's land area) (va 
Landa et al. 1997, p. 317), all of which occur within the distribution 
of the northern Mexican gartersnake. Miller et al. (2005, p. 60) stated 
that ``During the time we have collectively studied fishes in 
M[eacute]xico and southwestern United States, the entire biotas of long 
reaches of major streams such as the R[iacute]o Grande de Santiago 
below Guadalajara (Jalisco) and R[iacute]o Colorado (lower Colorado 
River in Mexico) downstream of Hoover (Boulder) Dam (in the United 
States), have simply been destroyed by pollution and river 
alteration.'' These streams are within the distribution of the northern 
Mexican gartersnake. The geographic extent of threats reported by 
Miller et al. (2005) across the distribution of the northern Mexican 
gartersnake in Mexico is evidence that they are widespread through the 
country, and encompass a large proportion of the distribution of the 
northern Mexican gartersnake in Mexico.
    In northern Mexico, effects of development, such as agriculture and 
irrigation practices on streams and rivers in Sonora have been 
documented at least as far back as the 1960s. Branson et al. (1960, p. 
218) found that the perennial rivers that drain the Sierra Madre are 
``silt-laden and extremely turbid, mainly because of irrigation 
practices.'' Smaller mountain streams,

[[Page 41532]]

such as the Rio Nacozari in Sonora were found to be ``biological 
deserts'' from the effects of numerous local mining practices (Branson 
et al. 1960, p. 218). These perennial rivers and their mountain 
tributaries were historically occupied by northern Mexican gartersnakes 
and their prey species whose populations have since been adversely 
affected and may be extirpated.
    Minckley et al. (2002, pp. 687-705) provided a summary of threats 
(p. 696) to three newly described (at the time) species of pupfish and 
their habitat in Chihuahua, Mexico, within the distribution of the 
northern Mexican gartersnake. Initial settlement and agricultural 
development of the area resulted in significant channel cutting through 
soil layers protecting the alluvial plain above them, which resulted in 
reductions in the base level of each basin in succession (Minckley et 
al. 2002, pp. 696). Related to these activities, the building of dams 
and diversion structures dried entire reaches of some regional streams 
and altered flow patterns of others (Minckley et al. 2002, pp. 696). 
This was followed by groundwater pumping (enhanced by the invention of 
the electric pump), which lowered groundwater levels and dried up 
springs and small channels and reduced the reliability of baseflow in 
``essentially all systems'' (Minckley et al. 2002, pp. 696). 
Subsequently, the introduction and expansion of nonnative species in 
the area successfully displaced or extirpated many native species 
(Minckley et al. 2002, pp. 696). Conant (1974, pp. 486-489) described 
significant threats to northern Mexican gartersnake habitat within its 
distribution in western Chihuahua, Mexico, and within the Rio Concho 
system where it occurs. These threats included impoundments, water 
diversions, and purposeful introductions of largemouth bass, common 
carp, and bullfrogs.
    In the central portions of the northern Mexican gartersnakes' range 
in Mexico, such as in Durango, Mexico, population growth since the 
1960s has led to regional effects such as reduced stream flow, 
increased water pollution, and largemouth bass introductions, which 
``have seriously affected native biota'' (Miller et al. 1989, p. 26). 
McCranie and Wilson (1987, p. 2) discuss threats to the pine-oak 
communities of higher elevation habitats within the distribution of the 
northern Mexican gartersnake in the Sierra Madre Occidental in Mexico, 
specifically noting that `` . . . the relative pristine character of 
the pine-oak woodlands is threatened . . . every time a new road is 
bulldozed up the slopes in search of new madera or pasturage. Once the 
road is built, further development follows; pueblos begin to pop up 
along its length. . . .'' Several drainages that possess suitable 
habitat for the northern Mexican gartersnake occur in the area 
referenced above by McCranie and Wilson (1987, p. 2) including the Rio 
de la Cuidad, Rio Quebrada El Salto, Rio Chico, Rio Las Bayas, Rio El 
Cigarrero, Rio Galindo, Rio Santa Barbara, and the Rio Chavaria.
    In the southern portion of the northern Mexican gartersnakes' range 
in Mexico, growth and development around Mexico City resulted in 
agricultural practices and groundwater demands that dewatered aquatic 
habitat and led to declines, and in some cases, extinctions of local 
native fish species (Miller et al. 1989, p. 25). In the region of 
southern Coahuila, Mexico, habitat modification and the loss of 
springs, water pollution, and irrigation practices has adversely 
affected native fish populations and led to the extinction of several 
native fish species (Miller et al. 1989, pp. 28-33). Considerable 
research has been focused in the central and west-central regions of 
Mexico, within the southern portion of the northern Mexican 
gartersnake's range, where native fish endemism (unique, narrowly 
distributed Suite of species) is high, as are threats to their 
populations and habitat. Since the 1970s in central Mexico, significant 
human population growth has resulted in the overexploitation of local 
fisheries and water pollution; these factors have accelerated the 
degradation of stream and riverine habitats and led to fish communities 
becoming reduced or undergoing significant changes in structure and 
composition (Mercado-Silva et al. 2002, p. 180). These shifts in fish 
community composition, population density, and shrinking distributions 
have adversely affected the northern Mexican gartersnake prey base in 
the southern portion of its range in Mexico. The Lerma River basin is 
the largest in west-central Mexico and is within the distribution of 
the northern Mexican gartersnake in the states of Jalisco, Guanajuato, 
and Quer[eacute]taro in the southern portion of its range. Lyons et al. 
(1995, p. 572) reported that many fish communities in large perennial 
rivers, isolated spring-fed streams, or spring sources themselves of 
this region have been ``radically restructured'' and are now dominated 
by a few nonnative, generalist species. Lowland streams and rivers in 
this region are used heavily for irrigation and are polluted by 
industrial, municipal, and agricultural discharges (Lyons and Navarro-
Perez 1990, p. 37; Lyons et al. 1995, p. 572).
    Native fish communities of west-central Mexico have been found to 
be in serious decline as a result of habitat degradation at an 
``unprecedented'' rate due to water withdrawals (diversions for 
irrigation), as well as untreated municipal, industrial, and 
agricultural discharges (Lyons et al. 1998, pp. 10-11). Numerous dams 
have been built along the Lerma River and along its major tributaries 
to support one of Mexico's most densely populated regions during the 
annual dry period; the water is used for irrigation, industry, and 
human consumption (Lyons et al. 1998, p. 11). From 1985 to 1993, Lyons 
et al. (1998, p. 12) found that 29 of 116 (25 percent) fish sampling 
locations visited within the Lerma River watershed were completely dry 
and another 30 were too polluted to support a fish community. These 
figures indicate that over half of the localities visited by Lyons et 
al. (1998, p. 12) that maintained fish populations prior to 1985 no 
longer support fish, which has likely led to local northern Mexican 
gartersnake population declines or extirpations. Soto-Galera et al. 
(1999, p. 137) reported fish and water quality sampling results from 20 
locations within the Rio Grande de Morelia-Lago de Cuitzeo Basin of 
Michoac[aacute]n and Guanajuato, Mexico, and found that over the past 
several decades, diminishing water quantity and worsening water quality 
have resulted in the elimination of 26 percent of native fish species 
from the basin, the extinction of two species of native fish, and 
declining distributions of the remaining 14 species. These figures 
provide evidence for widespread concern of native aquatic communities 
of this region, in particular for habitat and prey species of northern 
Mexican gartersnakes. Some conservation value, however, is realized 
when headwaters, springs, and small streams are protected as parks or 
municipal water supplies (Lyons et al. 1998, p. 15), but these efforts 
do little to protect larger perennial rivers that represent valuable 
habitat for northern Mexican gartersnakes.
    Mercado-Silva et al. (2002, Appendix 2) reported results from fish 
community sampling and habitat assessments along 63 sites across 
central Mexico, the eastern-most of which include most of the northern 
Mexican gartersnakes' southern range. Specifically, sampling locations 
in the Balsas, Lerma, Morelia, P[aacute]nuco Moctezuma, and 
P[aacute]nuco Tampa[oacute]n basins each occurred within the range of 
the northern Mexican gartersnake in the states of Guanajuato,

[[Page 41533]]

Queretaro, Mexico, and Puebla; approximately 30 locations in total. The 
purpose of this sampling effort was to score each site in terms of its 
index of biotic integrity (IBI) and environmental quality (EQ), with a 
score of 100 representing the optimum score for each category. The IBI 
scoring method has been verified as a valid means to quantitatively 
assess ecosystem integrity at each site (Lyons et al. 1995, pp. 576-
581; Mercado-Silva et al. 2002, p. 184). The range in IBI scores in 
these sampling locations was 85 to 35, and the range in EQ scores was 
90 to 50 (Mercado-Silva et al. 2002, Appendix 2). The average IBI score 
was 57, and the average EQ score was 74, across all 30 sites and all 
four basins (Mercado-Silva et al. 2002, Appendix 2). According to the 
qualitative equivalencies assigned to scores (Mercado-Silva et al. 
2002, p. 184), these values indicate that the environmental quality 
score averaged across all 30 sites was ``good'' and the biotic 
integrity scores were ``fair.'' It should be noted that 14 of the 30 
sites sampled had IBI scores equal to or less than 50, and five of 
those ranked as ``poor.'' Of all the basins throughout central Mexico 
that were scored in this exercise, the two P[aacute]nuco basins 
represented 20 of the 30 sites sampled and scored the worst of all 
basins (Mercado-Silva et al. 2002, p. 186). This indicates that threats 
to the northern Mexican gartersnake, its prey base, and its habitat 
pose the greatest risk in this portion of its range in Mexico.
    Near Torre[oacute]n, Coahuila, where the northern Mexican 
gartersnake occurs, groundwater pumping has resulted in flow reversal, 
which has dried up many local springs, drawn arsenic-laden water to the 
surface, and resulted in adverse human health effects in that area 
(Miller et al. 2005, p. 61). Severe water pollution from untreated 
domestic waste is evident downstream of large Mexican cities, such as 
Mexico City, and inorganic pollution from nearby industrialized areas 
and agricultural irrigation return flow has dramatically affected 
aquatic communities through contamination (Miller et al. 2005, p. 60). 
Miller et al. (2005, p. 61) provide an excerpt from Soto Galera et al. 
(1999) addressing the threats to the R[iacute]o Lerma, Mexico's longest 
river, which is occupied by the northern Mexican gartersnake: ``The 
basin has experienced a staggering amount of degradation during the 
20th Century. By 1985-1993, over half of our study sites had 
disappeared or become so polluted that they could no longer support 
fishes. Only 15 percent of the sites were still capable of supporting 
sensitive species. Forty percent (17 different species) of the native 
fishes of the basin had suffered major declines in distribution, and 
three species may be extinct. The extent and magnitude of degradation 
in the R[iacute]o Lerma basin matches or exceeds the worst cases 
reported for comparably sized basins elsewhere in the world.''
    In the Transvolcanic Belt Region of the states of Jalisco, Mexico, 
and Veracruz in southern Mexico, Conant (2003, p. 4) noted that water 
diversions, pollution (e.g., discharge of raw sewage), sedimentation of 
aquatic habitats, and increased dissolved nutrients were resulting in 
decreased dissolved oxygen in suitable northern Mexican gartersnake 
habitat. Conant (2003, p. 4) stated that many of these threats were 
evident during his field work in the 1960s, and that they are 
``continuing with increased velocity.''
High-Intensity Wildfires and Sedimentation of Aquatic Habitat
    Low-intensity fire has been a natural disturbance factor in 
forested landscapes for centuries, and low-intensity fires were common 
in southwestern forests prior to European settlement (Rinne and Neary 
1996, pp. 135-136). Rinne and Neary (1996, p. 143) discuss effects of 
recent fire management policies on aquatic communities in Madrean Oak 
Woodland biotic communities in the southwestern United States. They 
concluded that existing wildfire suppression policies intended to 
protect the expanding number of human structures on forested public 
lands have altered the fuel loads in these ecosystems and increased the 
probability of high-intensity wildfires. The effects of these high-
intensity wildfires include the removal of vegetation, the degradation 
of subbasin condition, altered stream behavior, and increased 
sedimentation of streams. These effects can harm fish communities, as 
observed in the 1990 Dude Fire, when corresponding ash flows resulted 
in fish kills in Dude Creek and the East Verde River (Voeltz 2002, p. 
77). Fish kills, also discussed below, can drastically affect the 
suitability of habitat for northern Mexican and narrow-headed 
gartersnakes due to the removal of a portion or the entire prey base. 
The Chiricahua leopard frog recovery plan cites altered fire regimes as 
a serious threat to Chiricahua leopard frogs, a prey species for 
northern Mexican gartersnakes (USFWS 2007, pp. 38-39).
    The nature and occurrence of wildfires in the Southwest is expected 
to also be affected by climate change and ongoing drought. Current 
predictions of drought and/or higher winter low temperatures may stress 
ponderosa pine forests in which the narrow-headed gartersnake 
principally occurs, and may increase the frequency and magnitude of 
wildfire. Ganey and Vojta (2010, entire) studied tree mortality in 
mixed conifer and ponderosa pine forests in Arizona from 1997-2007, a 
period of extreme drought. They found the mortality of trees to be 
severe; the number of trees dying over a 5[hyphen]year period increased 
by over 200 percent in mixed[hyphen]conifer forest and by 74 percent in 
ponderosa pine forest during this time frame. Ganey and Vojta (2010) 
attributed drought and subsequent insect (bark beetle) infestation to 
the die-offs in trees. Drought stress and a subsequent high degree of 
tree mortality from bark beetles make high-elevation forests more 
susceptible to high-intensity wildfires. Climate is a top-down factor 
that synchronizes with fuel loads, a bottom-up factor. Combined with a 
predicted reduction in snowpack and an earlier snowmelt, these factors 
suggest wildfires will be larger, more frequent, and more severe in the 
southwestern United States (Ful[eacute] 2010). Wildfires are expected 
to reduce vegetative cover and result in greater soil erosion, 
subsequently resulting in increased sediment flows in streams 
(Ful[eacute] 2010, entire). Increased sedimentation in streams reduces 
the visibility of gartersnakes in the water column, hampering their 
hunting ability as well as resulting in fish kills (which is also 
caused by the disruption in the nitrogen cycle post-wildfire), which 
reduce the amount of prey available to gartersnake populations. 
Additionally, unnaturally high amounts of sediment fill in pools in 
intermittent streams, which reduces the amount and availability of 
habitat for fish and amphibian prey.
    In the last 2 years, both Arizona (2011 Wallow Fire) and New Mexico 
(2012 Whitewater-Baldy Complex Fire) have experienced the largest 
wildfires in their respective State histories; indicative of the last 
decade that has been punctuated by wildfires of massive proportion. The 
2011 Wallow Fire consumed approximately 540,000 acres (218,530 ha) of 
Apache-Sitgreaves National Forest, White Mountain Apache Indian Tribe, 
and San Carlos Apache Indian Reservation lands in Apache, Navajo, 
Graham, and Greenlee counties in Arizona as well as Catron County, New 
Mexico (InciWeb 2011). The 2011 Wallow Fire impacted 97 percent of 
perennial streams in the Black River subbasin, 70 percent of perennial 
streams in the Gila River subbasin, and

[[Page 41534]]

78 percent of the San Francisco River subbasin and resulted in 
confirmed fish kills in each subbasin (Meyer 2011; p. 3, Table 2); each 
of these streams is known to support populations of either northern 
Mexican or narrow-headed gartersnakes.
    Although the Black River drainage received no moderate or high-
severity burns as a result of the 2011 Wallow Fire, the Fish and Snake 
Creek subbasins (tributaries to the Black River) were severely burned 
(Coleman 2011, p. 2). Post-fire fisheries surveys above Wildcat Point 
in the Black River found no fish in a reach extending up to the 
confluence with the West Fork of Black River. This was likely due to 
subsequent ash and sediment flows that had occurred there (Coleman 
2011, p. 2). Post-fire fisheries surveys at ``the Box,'' in the Blue 
River, detected only a single native fish. This was also likely due to 
ash and sediment flows and the associated subsequent fish kills that 
had occurred there, extending down to the Gila River Box in Safford, 
Arizona (Coleman 2011, pp. 2-3). The East Fork Black River subbasin 
experienced moderate to high-severity burns in 23 percent of its total 
acreage that resulted in declines in Apache trout and native sucker 
populations, but speckled dace and brown trout remained prevalent as of 
2011 (Coleman 2011, p. 3). These fire data suggest that the persistence 
of the prey base for northern Mexican and narrow-headed gartersnakes in 
the Black River, and narrow-headed gartersnakes in the lower Blue 
River, will be precarious into the near- to midterm future, as will 
likely be the stability of gartersnake populations there.
    Several large wildfires, which have resulted in excessive 
sedimentation of streams and affected resident fish populations that 
serve as prey for narrow-headed gartersnakes, have occurred 
historically on the Gila National Forest. From 1989-2004, numerous 
wildfires cumulatively burned much of the uplands within the Gila 
National Forest, which resulted in most perennial streams in the area 
experiencing ash flows and elevated sedimentation (Paroz et al. 2006, 
p. 55). More recently, the 2012 Whitewater-Baldy Complex Fire in the 
Gila National Forest in New Mexico is the largest wildfire in that 
State's history. This wildfire was active for more than 5 weeks and 
consumed approximately 300,000 acres (121,406 ha) of ponderosa, mixed 
conifer, pinyon-juniper, and grassland habitat (InciWeb 2012). Over 25 
percent of the burn area experienced high-moderate burn severity 
(InciWeb 2012) and included several subbasins occupied by narrow-headed 
gartersnakes such as the Middle Fork Gila River, West Fork Gila River, 
Iron Creek, the San Francisco River, Whitewater Creek, and Mineral 
Creek (Brooks 2012, Table 1). Other extant populations of the narrow-
headed gartersnake in Gilita and South Fork Negrito Creeks are also 
expected to be impacted from the 2012 Whitewater-Baldy Complex Fire. 
Narrow-headed gartersnake populations in the Middle Fork Gila River and 
Whitewater Creek formerly represented two of the four most robust 
populations known from New Mexico, and two of the five known rangewide, 
and are expected to have been severely jeopardized by post-fire effects 
to their prey base. Thus, we now consider them currently as likely not 
viable, at least in the short to medium term. In reference to Gila 
trout populations, Brooks (2012, p. 3) stated that fish populations are 
expected to be severely impacted in the West Fork Gila River and 
Whitewater Creek. The loss of fish communities in affected streams is 
likely to lead to associated declines, or potential extirpations, in 
affected narrow-headed gartersnake populations as a result of the 
collapse in their prey base.
    Since 2000, several wildfires have affected occupied narrow-headed 
gartersnake habitat on the Gila National Forest. The West Fork Gila 
subbasin was affected by the 2002 Cub Fire, the 2003 Dry Lakes Fire, 
and the 2011 Miller Fire; each resulted in post-fire ash and sediment 
flows, which adversely affected fish populations used by narrow-headed 
gartersnakes (Hellekson 2012a, pers. comm.). In 2011, the Miller Fire 
significantly affected the Little Creek subbasin and has resulted in 
substantive declines in abundance of the fish community (Hellekson 
2012a, pers. comm.). Dry Blue and Campbell Blue creeks were affected by 
the 2011 Wallow Fire (Hellekson 2012a, pers. comm.). Saliz Creek was 
highly affected by the 2006 Martinez Fire (Hellekson 2012a, pers. 
comm.). Turkey Creek was heavily impacted by the Dry Lakes Fire in 
2002, which resulted in a complete fish kill, but the fish community 
has since rebounded (Hellekson 2012a, pers. comm.). It is not certain 
how long the fish community was sparse or absent from Turkey Creek, but 
it is suspected that the narrow-headed gartersnake population there 
suffered significant declines from the loss of their prey base, as 
evidenced by the current low population numbers. Prior to the 2002 Dry 
Lakes Fire, Turkey Creek was largely populated by nonnative, spiny-
rayed fish species, but has since been recolonized by native fish 
species almost exclusively (Hellekson 2012a, pers. comm.), and may 
provide high-quality habitat for narrow-headed gartersnakes, once the 
subbasin has adequately stabilized.
    Affects to northern Mexican and narrow-headed gartersnake habitat 
from wildfire should be considered in light of effects to the 
structural habitat and effects to the prey base. Post-fire effects vary 
with burn severity, percent of area burned within each severity 
category, and the intensity and duration of precipitation events that 
follow (Coleman 2011, p. 4). Low-severity burns within riparian habitat 
can actually have a rejuvenating effect by removing decadent ground 
cover and providing nutrients to remaining vegetation. As a result, 
riparian vegetative communities may be more resilient to wildfire, 
given that water is present (Coleman 2011, p. 4). Willows, an important 
component to narrow-headed gartersnake habitat, can be positively 
affected by low-severity burns, as long as the root crowns are not 
damaged (Coleman 2011, p. 4). High severity burns that occur within the 
floodplain of occupied habitat are expected to have some level of 
shorter-term effect on resident gartersnake populations through effects 
to the vegetative structure and abundance, which may include a 
reduction of basking sites and a loss of cover, which could increase 
the risk of predation. These potential effects need further study. 
Post-fire ash flows, flooding, and impacts to native prey populations 
are longer term effects and can occur for many years after a large 
wildfire (Coleman 2011, p. 2).
    Post-fire flooding with significant ash and sediment loads can 
result in significant declines, or even the collapse, of resident fish 
communities, which poses significant concern for the persistence of 
resident gartersnake populations in affected areas. Sedimentation can 
adversely affect fish populations used as prey by northern Mexican or 
narrow-headed gartersnakes by: (1) Interfering with respiration; (2) 
reducing the effectiveness of fish's visually based hunting behaviors; 
and (3) filling in interstitial (spaces between cobbles, etc., on the 
stream floor) spaces of the substrate, which reduces reproduction and 
foraging success of fish (Wheeler et al. 2005, p. 145). Excessive 
sediment also fills in intermittent pools required for amphibian prey 
reproduction and foraging. Siltation of the rocky interstitial spaces 
along stream bottoms decreases the dissolved oxygen content where fish 
lay their eggs, resulting in depressed recruitment of fish and a

[[Page 41535]]

subsequent reduction in prey abundance for northern Mexican and narrow-
headed gartersnakes through the loss of prey microhabitat (Nowak and 
Santana-Bendix 2002, pp. 37-38). As stated above, sediment can lead to 
several effects in resident fish species used by northern Mexican or 
narrow-headed gartersnakes as prey, which can ultimately cause 
increased direct mortality, reduced reproductive success, lower overall 
abundance, and reductions in prey species composition as documented by 
Wheeler et al. (2005, p. 145). The underwater foraging ability of 
narrow-headed gartersnakes (de Queiroz 2003, p. 381) and likely 
northern Mexican gartersnakes is largely based on vision and is also 
directly compromised by excessive turbidity caused by sedimentation of 
water bodies. Suspended sediment in the water column may reduce the 
narrow-headed gartersnake's visual hunting efficiency from effects to 
water clarity, based on research conducted by de Queiroz (2003, p. 381) 
that concluded the species relied heavily on visual cues during 
underwater striking behaviors.
    The presence of adequate interstitial spaces along stream floors 
may be particularly important for narrow-headed gartersnakes. Hibbitts 
and Fitzgerald (2009, p. 464) reported the precipitous decline of 
narrow-headed gartersnakes in a formerly robust population in the San 
Francisco River at San Francisco Hot Springs from 1996 to 2004. The 
exact cause for this significant decline is uncertain, but the 
investigators suspected that a reduction in interstitial spaces along 
the stream floor from an apparent conglomerate, cementation process may 
have affected the narrow-headed gartersnake's ability to successfully 
anchor themselves to the stream bottom when seeking refuge or foraging 
for fish (Hibbitts and Fitzgerald 2009, p. 464). These circumstances 
would likely result in low predation success and eventually starvation. 
Other areas where sedimentation has affected either northern Mexican or 
narrow-headed gartersnake habitat are Cibecue Creek in Arizona, and the 
San Francisco River and South Fork Negrito Creek in New Mexico (Rosen 
and Schwalbe 1988, p. 46; Arizona Department of Water Resources 2011, 
p. 1; Hellekson 2012a, pers. comm.). The San Francisco River in Arizona 
was classified as impaired due to excessive sediment from its 
headwaters downstream to the Arizona-New Mexico border (Arizona 
Department of Water Resources 2011, p. 1). South Fork Negrito Creek is 
also listed as impaired due to excessive turbidity (Hellekson 2012a, 
pers. comm.).
    Summary--The presence of water is critical to both northern Mexican 
and narrow-headed gartersnakes and their primary prey species because 
their ecology and natural histories are strongly linked to water. 
Several factors, both natural and manmade, contribute to the continued 
degradation and dewatering of aquatic habitat throughout the range of 
northern Mexican and narrow-headed gartersnakes. Increasing human 
population growth is driving higher and higher demands for water in 
both the United States and Mexico. Water is subsequently secured 
through dams, diversions, flood-control projects, and groundwater 
pumping, which affects gartersnake habitat through reductions in flow 
and complete dewatering of stream reaches. Entire reaches of the Gila, 
Salt, Santa Cruz, and San Francisco Rivers, as well as numerous other 
rivers throughout the Mexican Plateau in Mexico which were historically 
occupied by either or both northern Mexican or narrow-headed 
gartersnakes, are now completely dry due to diversions, dams, and 
groundwater pumping. Several groundwater basins within the range of 
northern Mexican and narrow-headed gartersnakes in the United States 
are considered active management areas where pumping exceeds recharge, 
which is a constant threat to surface flow in streams and rivers 
connected to these aquifers. Reduced flows concentrate northern Mexican 
and narrow-headed gartersnakes and their prey with harmful nonnative 
species, which accelerate and amplify adverse effects of native-
nonnative community interactions. Where surface water persists, 
increasing land development and recreation use adjacent to and within 
riparian habitat has led to further reductions in stream flow, removal 
or alteration of vegetation, and increased frequency of adverse human 
interactions with gartersnakes.
    Exacerbating the effects of increasing human populations and higher 
water demands, climate change predictions include increased aridity, 
lower annual precipitation totals, lower snow pack levels, higher 
variability in flows (lower low-flows and higher high-flows), and 
enhanced stress on ponderosa pine communities in the southwestern 
United States and northern Mexico. Increased stress to ponderosa pine 
forests places them at higher risk of high-intensity wildfires, the 
effects of which are discussed below. Climate change has also been 
predicted to enhance the abundance and distribution of harmful 
nonnative species, which adversely affect northern Mexican and narrow-
headed gartersnakes.
    Cienegas, a unique and important habitat for northern Mexican 
gartersnakes, have been adversely affected or eliminated by a variety 
of historical and current land uses in the United States and Mexico, 
including streambed modification, intensive livestock grazing, 
woodcutting, artificial drainage structures, stream flow stabilization 
by upstream dams, channelization, and stream flow reduction from 
groundwater pumping and water diversions. The historical loss of the 
cienega habitat of the northern Mexican gartersnake has resulted in 
local population declines or extirpations, negatively affecting its 
status and contributing to its decline rangewide.
    Wildfire has historically been a natural and important disturbance 
factor within the range of northern Mexican and narrow-headed 
gartersnakes. However, in recent decades, forest management policies in 
the United States have favored fire suppression, the result of which 
has led to wildfires of unusual proportions, particularly along the 
Mogollon Rim of Arizona and New Mexico. These policies are generally 
not in place in Mexico, and consequently, wildfire is not viewed as a 
significant threat to the northern Mexican gartersnake in Mexico. 
However, in the last 2 years, both Arizona (2011 Wallow Fire) and New 
Mexico (2012 Whitewater-Baldy Complex Fire) have experienced the 
largest wildfires in their respective State histories, which is 
indicative of the last decade having been punctuated by wildfires of 
significant magnitude. High-intensity wildfire has been shown to result 
in significant ash and sediment flows into habitat occupied by northern 
Mexican or narrow-headed gartersnakes, resulting in significant 
reductions of their fish prey base and, in some instances, total fish 
kills. The interstitial spaces between rocks located along the stream 
floor are important habitat for the narrow-headed gartersnake as a 
result of its specialized foraging strategy and specialized diet. They 
area also important for several fish species relied upon as prey. When 
these spaces fill in with sediment, the narrow-headed gartersnake may 
be unable to forage successfully and may succumb to stress created by a 
depressed prey base. A significant reduction or absence of a prey base 
results in stress of resident gartersnake populations and can result in 
local population extirpations. Also, narrow-headed gartersnakes are 
believed to rely heavily on visual cues

[[Page 41536]]

while foraging underwater; increased turbidity from suspended fine 
sediment in the water column is likely to impede their ability to use 
visual cues at some level. Factors that result in depressed foraging 
ability from excessive sedimentation are likely to be enhanced when 
effects from harmful nonnative species are also acting on resident 
northern Mexican and narrow-headed gartersnake populations. We consider 
the narrow-headed gartersnake to be particularly threatened by the 
effects of wildfires as described because they occur throughout its 
range, the species is a fish-eating specialist that is unusually 
vulnerable to localized fish kills, and wildfire has already 
significantly affected two of the last remaining five populations that 
were formerly considered viable, pre-fire. We have demonstrated that 
high-intensity wildfires have the potential to eliminate gartersnake 
populations through a reduction or loss of their prey base. Since 1970, 
wildfires have adversely impacted the native fish prey base in 6 
percent of the historical distribution of northern Mexican gartersnakes 
in the United States and 21 percent of that for narrow-headed 
gartersnakes rangewide, according to GIS analysis.
    All of these conditions affect the primary drivers of gartersnake 
habitat suitability (the presence of water and prey) and exist in 
various degrees throughout the range of both gartersnake species. 
Collectively, they reduce the amount and arrangement of physically 
suitable habitat for northern Mexican and narrow-headed gartersnakes 
over their regional landscapes. The genetic representation of each 
species is threatened when populations become disconnected and isolated 
from neighboring populations because the length or area of dewatered 
zones is too great for dispersing individuals to overcome. Therefore, 
normal colonizing mechanisms that would otherwise reestablish 
populations where they have become extirpated are no longer viable. 
This subsequently leads to a reduction in species redundancy when 
isolated, small populations are at increased vulnerability to the 
effects of stochastic events, without a means for natural 
recolonization. Ultimately, the effects of scattered, small, and 
disjunct populations, without the means to naturally recolonize, is 
weakened species resiliency as a whole, which ultimately enhances the 
risk of either or both species becoming endangered or going extinct. 
Therefore, based on the best available scientific and commercial 
information, we conclude that land uses or conditions described above 
that alter or dewater northern Mexican and narrow-headed gartersnake 
habitat are threats rangewide, now and in the foreseeable future.

The Cumulative and Synergistic Effect of Threats on Low-Density 
Northern Mexican and Narrow-Headed Gartersnake Populations

    In most locations where northern Mexican or narrow-headed 
gartersnakes historically occurred or still occur currently, two or 
more threats are likely acting in combination with regard to their 
influence on the suitability of those habitats or on the species 
themselves. Many threats could be considered minor in isolation, but 
when they affect gartersnake populations in combination with other 
threats, become more serious. We have concluded that in as many as 24 
of 29 known localities in the United States (83 percent), the northern 
Mexican gartersnake population is likely not viable and may exist at 
low population densities that could be threatened with extirpation or 
may already be extirpated. We also determined that in as many as 29 of 
38 known localities (76 percent), the narrow-headed gartersnake 
population is likely not viable and may exist at low population 
densities that could be threatened with extirpation or may already be 
extirpated but survey data are lacking in areas where access is 
restricted. We have also discussed how harmful nonnative species have 
affected recruitment of gartersnakes across their range. In viable 
populations, gartersnakes are resilient to the loss of individuals 
through ongoing recruitment into the reproductive age class. However, 
when northern Mexican or narrow-headed gartersnakes occur at low 
population densities in the absence of appropriate recruitment, the 
loss of even a few adults, or even a single adult female, could drive a 
local population to extirpation. Below, we discuss threats that, when 
considered in combination, can appreciably threaten low-density 
populations with extirpation.
Historical and Unmanaged Livestock Grazing and Agricultural Land Uses
    Currently in the United States, livestock grazing is a largely 
managed activity, but in Mexico, livestock grazing is much less managed 
or unmanaged altogether. The effect of livestock grazing on resident 
gartersnake populations must be examined as a comparison between 
historical and current management, and in the presence of harmful 
nonnative species, or not. Historical livestock grazing has damaged 
approximately 80 percent of stream, cienega, and riparian ecosystems in 
the western United States (Kauffman and Krueger 1984, pp. 433-435; 
Weltz and Wood 1986, pp. 367-368; Cheney et al. 1990, pp. 5, 10; Waters 
1995, pp. 22-24; Pearce et al. 1998, p. 307; Belsky et al. 1999, p. 1). 
Fleischner (1994, p. 629) found that ``Because livestock congregate in 
riparian ecosystems, which are among the most biologically rich 
habitats in arid and semiarid regions, the ecological costs of grazing 
are magnified at these sites.'' Stromberg and Chew (2002, p. 198) and 
Trimble and Mendel (1995, p. 243) also discussed the propensity for 
cattle to remain within or adjacent to riparian communities. 
Expectedly, this behavior is more pronounced in more arid regions 
(Trimble and Mendel 1995, p. 243). Effects from historical or unmanaged 
grazing include: (1) Declines in the structural richness of the 
vegetative community; (2) losses or reductions of the prey base; (3) 
increased aridity of habitat; (4) loss of thermal cover and protection 
from predators; (5) a rise in water temperatures to levels lethal to 
larval stages of amphibian and fish development; and (6) 
desertification (Szaro et al. 1985, p. 362; Schulz and Leininger 1990, 
p. 295; Schlesinger et al. 1990, p. 1043; Belsky et al. 1999, pp. 8-11; 
Zwartjes et al. 2008, pp. 21-23). In one rangeland study, it was 
concluded that 81 percent of the vegetation that was consumed, 
trampled, or otherwise removed was from a riparian area, which amounted 
to only 2 percent of the total grazing space, and that these actions 
were 5 to 30 times higher in riparian areas than on the uplands 
(Trimble and Mendel 1995, pp. 243-244). However, according to one study 
along the Agua Fria River, herbaceous ground cover can recover quickly 
from heavy grazing pressure (Szaro and Pase 1983, p. 384). Additional 
information on the effects of historical livestock grazing can be found 
in Sartz and Tolsted (1974, p. 354); Rosen and Schwalbe (1988, pp. 32-
33, 47); Clary and Webster (1989, p. 1); Clary and Medin (1990, p. 1); 
Orodho et al. (1990, p. 9); and Krueper et al. (2003, pp. 607, 613-
614).
    Szaro et al. (1985, p. 360) assessed the effects of historical 
livestock management on a sister taxon and found that western 
(terrestrial) gartersnake (Thamnophis elegans vagrans) populations were 
significantly higher (versus controls) in terms of abundance and 
biomass in areas that were excluded from grazing, where the streamside 
vegetation remained lush, than where uncontrolled access to grazing was 
permitted. This effect was

[[Page 41537]]

complemented by higher amounts of cover from organic debris from 
ungrazed shrubs that accumulate as the debris moves downstream during 
flood events. Specifically, results indicated that snake abundance and 
biomass were significantly higher in ungrazed habitat, with a five-fold 
difference in number of snakes captured, despite the difficulty of 
making observations in areas of increased habitat complexity (Szaro et 
al. 1985, p. 360). Szaro et al. (1985, p. 362) also noted the 
importance of riparian vegetation for the maintenance of an adequate 
prey base and as cover in thermoregulation and predation avoidance 
behaviors, as well as for foraging success. Direct mortality of 
amphibian species, in all life stages, from being trampled by livestock 
has been documented in the literature (Bartelt 1998, p. 96; Ross et al. 
1999, p. 163). Gartersnakes may, on occasion, be trampled by livestock. 
A black-necked gartersnake (Thamnophis cyrtopsis cyrtopsis) had 
apparently been killed by livestock trampling along the shore of a 
stock tank in the Apache-Sitgreaves National Forest, within an actively 
grazed allotment (Chapman 2005).
    Subbasins where historical grazing has been documented as a 
suspected contributing factor for either northern Mexican or narrow-
headed gartersnake declines include the Verde, Salt, Agua Fria, San 
Pedro, Gila, and Santa Cruz (Hendrickson and Minckley 1984, pp. 140, 
152, 160-162; Rosen and Schwalbe 1988, pp. 32-33; Girmendonk and Young 
1997, p. 47; Hale 2001, pp. 32-34, 50, 56; Voeltz 2002, pp. 45-81; 
Krueper et al. 2003, pp. 607, 613-614; Forest Guardians 2004, pp. 8-10; 
Holycross et al. 2006, pp. 52-61; McKinnon 2006d, 2006e; Paradzick et 
al. 2006, pp. 90-92; USFS 2008). Livestock grazing still occurs in 
these subbasins but is a largely managed land use and is not likely to 
pose significant threats to either northern Mexican or narrow-headed 
gartersnakes where closely managed. In cases where poor livestock 
management results in fence lines in persistent disrepair, providing 
unmanaged livestock access to occupied habitat, adverse effects from 
loss of vegetative cover may result, most likely in the presence of 
harmful nonnative species. As we described above, however, we strongly 
suspect that northern Mexican and narrow-headed gartersnakes are 
somewhat resilient to physical habitat disturbance where harmful 
nonnative species are absent.
    The creation and maintenance of stock tanks is an important 
component to livestock grazing in the southwestern United States. Stock 
tanks associated with livestock grazing may facilitate the spread of 
harmful nonnative species when they are intentionally or 
unintentionally stocked by anglers and private landowners (Rosen et al. 
2001, p. 24). The management of stock tanks is an important 
consideration for northern Mexican gartersnakes in particular. Stock 
tanks associated with livestock grazing can be intermediary ``stepping 
stones'' in the dispersal of nonnative species from larger source 
populations to new areas (Rosen et al. 2001, p. 24). The effects of 
livestock grazing at stock tanks on northern Mexican gartersnakes 
depend on how they are managed. Dense bank and aquatic vegetation is an 
important habitat characteristic for the northern Mexican gartersnake 
in the presence of harmful nonnative species. This vegetation can be 
affected if the impoundment is poorly managed. When harmful nonnative 
species are absent, the presence of bank line vegetation is less 
important. Well-managed stock tanks provide important habitat for 
northern Mexican gartersnakes and their prey base, especially when the 
tank: (1) Remains devoid of harmful nonnative species while supporting 
native prey species; (2) provides adequate vegetation cover; and (3) 
provides reliable water sources in periods of prolonged drought. Given 
these benefits of well-managed stock tanks, we believe well-managed 
stock tanks are an important, even vital, component to northern Mexican 
gartersnake conservation and recovery.
Road Construction, Use, and Maintenance
    Roads can pose unique threats to herpetofauna, and specifically to 
species like the northern Mexican gartersnake, its prey base, and the 
habitat where it occurs. The narrow-headed gartersnake, alternatively, 
is probably less affected by roads due to its more aquatic nature. 
Roads fragment occupied habitat and can result in diminished genetic 
viability in populations from increased mortality from vehicle strikes 
and adverse human encounters as supported by current research on 
eastern indigo snakes (Breininger et al. 2012, pp. 364-366). Roads 
often track along streams and present a mortality risk to gartersnakes 
seeking more upland, terrestrial habitat for brumation and gestation. 
Roads may cumulatively impact both species through the following 
mechanisms: (1) Fragmentation, modification, and destruction of 
habitat; (2) increase in genetic isolation; (3) alteration of movement 
patterns and behaviors; (4) facilitation of the spread of nonnative 
species via human vectors; (5) an increase in recreational access and 
the likelihood of subsequent, decentralized urbanization; (6) 
interference with or inhibition of reproduction; (7) contributions of 
pollutants to riparian and aquatic communities; (8) reduction of prey 
communities; (9) effects to gartersnake reproduction; and (10) acting 
as population sinks (when population death rates exceed birth rates in 
a given area) (Rosen and Lowe 1994, pp. 146-148; Waters 1995, p. 42; 
Foreman and Alexander 1998, p. 220; Trombulak and Frissell 2000, pp. 
19-26; Carr and Fahrig 2001, pp. 1074-1076; Hels and Buchwald 2001, p. 
331; Smith and Dodd 2003, pp. 134-138; Angermeier et al. 2004, pp. 19-
24; Shine et al. 2004, pp. 9, 17-19; Andrews and Gibbons 2005, pp. 777-
781; Wheeler et al. 2005, pp. 145, 148-149; Roe et al. 2006, p. 161; 
Sacco 2007, pers. comm.; Ouren et al. 2007, pp. 6-7, 11, 16, 20-21; 
Jones et al. 2011, pp. 65-66; Hellekson 2012a, pers. comm.).
    Perhaps the most common factor in road mortality of snakes is the 
propensity for drivers to unintentionally and intentionally run them 
over, both because people tend to dislike snakes (Rosen and Schwalbe 
1988, p. 43; Ernst and Zug 1996, p. 75; Green 1997, pp. 285-286; Nowak 
and Santana-Bendix 2002, p. 39) and because they make easy targets 
crossing roads at perpendicular angles (Klauber 1956, p. 1026; Langley 
et al. 1989, p. 47; Shine et al. 2004, p. 11). Mortality data for 
northern Mexican gartersnakes have been collected at the Bubbling Ponds 
Hatchery since 2006. Of the 15 dead specimens, eight were struck by 
vehicles on roads within or adjacent to the hatchery ponds, perhaps 
while crossing between ponds to forage (Boyarski 2011, pp. 1-3). Van 
Devender and Lowe (1977, p. 47), however, observed several northern 
Mexican gartersnakes crossing the road at night after the commencement 
of the summer monsoon (rainy season), which highlights the seasonal 
variability in surface activity of this snake. Wallace et al. (2008, 
pp. 243-244) documented a vehicle-related mortality of a northern 
Mexican gartersnake on Arizona State Route 188 near Tonto Creek that 
occurred in 1995.
Adverse Human Interactions With Gartersnakes
    A fear of snakes is generally and universally embedded in modern 
culture, and is prevalent in the United States (Rosen and Schwalbe 
1988, p. 43; Ernst and Zug 1996, p. 75; Green 1997, pp. 285-286; Nowak 
and Santana-Bendix 2002, p. 39). We use the phrase ``adverse human 
interaction'' to refer to the act of humans directly injuring or

[[Page 41538]]

killing snakes out of a sense of fear or anxiety (ophidiophobia), or 
for no apparent purpose. One reason the narrow-headed gartersnake is 
vulnerable to adverse human interactions is because of its appearance. 
The narrow-headed gartersnake is often confused for a venomous water 
moccasin (cottonmouth, Agkistrodon piscivorus), because of its 
triangular-shaped head and propensity to be found in or near water 
(Nowak and Santana-Bendix 2002, p. 38). Although the nearest water 
moccasin populations are located over 700 miles (1,127 km) to the east 
in central Texas, these misidentifications prove fatal for narrow-
headed gartersnakes (Nowak and Santana-Bendix 2002, p. 38).
    Adverse human interaction may be largely responsible for highly 
localized extirpations in narrow-headed gartersnakes based on the 
collection history of the species at Slide Rock State Park along Oak 
Creek, where high recreation use is strongly suspected to result in 
direct mortality of snakes by humans (Nowak and Santana-Bendix 2002, 
pp. 21, 38). Rosen and Schwalbe (1988, p. 42-43) suggested that 
approximately 44 percent of the estimated annual mortality of narrow-
headed gartersnakes in the larger size classes along Oak Creek may be 
human-caused. Declines in narrow-headed gartersnake populations in the 
North and East Forks of the White River have also been attributed to 
humans killing snakes (Rosen and Schwalbe 1988, pp. 43-44). Locations 
in New Mexico where this unnatural form of mortality is believed to 
have historically affected or currently affect narrow-headed 
gartersnakes include Wall Lake (Fleharty 1967, p. 219), Middle Fork of 
the Gila River, the mainstem Gila River from Cliff Dwellings to Little 
Creek, in Whitewater Creek from the Catwalk to Glenwood (L. Hellekson 
2012a, pers. comm.), and near San Francisco Hot Springs along the San 
Francisco River (Hibbitts and Fitzgerald 2009, p. 466).
Environmental Contaminants
    Environmental contaminants, such as heavy metals, may be common at 
low background levels in soils and, as a result, concentrations are 
known to bioaccumulate in food chains. A bioaccumulative substance 
increases in concentration in an organism or in the food chain over 
time. A mid- to higher-order predator, such as a gartersnake, may, 
therefore, accumulate these types of contaminants over time in their 
fatty tissues, which may lead to adverse health effects (Wylie et al. 
2009, p. 583, Table 5). Campbell et al. (2005, pp. 241-243) found that 
metal concentrations accumulated in the northern watersnake (Nerodia 
sipedon) at levels six times that of their primary prey item, the 
central stoneroller (a fish, Campostoma anomalum). Metals, in trace 
amounts, can be sequestered in the skin of snakes (Burger 1999, p. 
212), interfere with metabolic rates of snakes (Hopkins et al. 1999, p. 
1261), affect the structure and function of their liver and kidneys, 
and may also act as neurotoxins, affecting nervous system function 
(Rainwater et al. 2005, p. 670). Based on data collected in 2002-2010, 
mercury appears to be bioaccumulating in fish found in the lower 
reaches of Tonto Creek, where northern Mexican gartersnakes also occur 
(Rector 2010, pers. comm.). In fact, the State record for the highest 
mercury concentrations in fish tissue was reported in Tonto Creek from 
this investigation by Rector (2010, pers. comm.). Mercury levels were 
found to be the highest in the piscivorous smallmouth bass and, 
secondly, in desert suckers (a common prey item for northern Mexican 
and narrow-headed gartersnakes). Because gartersnakes eat fish, mercury 
may be bioaccumulating in resident populations, although no testing has 
occurred.
    Specific land uses such as mining and smelting, as well as road 
construction and use, can be significant sources of contaminants in 
air, water, or soil through point-source and non-point source 
mechanisms. Copper mining has occurred in Arizona (Pima, Pinal, 
Yavapai, and Gila Counties) and adjacent Mexico for centuries, and many 
of these sites have smelters (now decommissioned), which are former 
sources of airborne contaminants. The mining industry in Mexico is 
largely concentrated in the northern tier of that country, with the 
State of Sonora being the leading producer of copper, gold, graphite, 
molybdenum, and wollastonite, as well as the leader among Mexican 
States with regard to the amount of surface area dedicated to mining 
(Stoleson et al. 2005, p. 56). The three largest mines in Mexico (all 
copper) are found in Sonora (Stoleson et al. 2005, p. 57). The sizes of 
mines in Sonora vary considerably, as do the known environmental 
effects from mining-related activities (from exploration to long after 
closure), which include contamination and drawdown of groundwater 
aquifers, erosion, acid mine drainage, fugitive dust, pollution from 
smelter emissions, and landscape clearing (Stoleson et al. 2005, p. 
57). We are aware of no specific research on potential effects of 
mining or environmental contaminants acting on northern Mexican 
gartersnakes in Mexico, but presume, based on the best available 
scientific and commercial information, that where this land use is 
prevalent, contaminants may be a contributing threat to resident 
gartersnakes or their prey.
Northern Mexican Gartersnake Competition With Marcy's Checkered 
Gartersnake
    Preliminary research suggests that Marcy's checkered gartersnake 
(Thamnophis marcianus marcianus) may impact the future conservation of 
the northern Mexican gartersnake in southern Arizona, although 
supporting data are limited. Rosen and Schwalbe (1988, p. 31) 
hypothesized that bullfrogs are more likely to eliminate northern 
Mexican gartersnakes when Marcy's checkered gartersnakes are also 
present. Marcy's checkered gartersnake is a semi-terrestrial species 
that is able to co-exist to some degree with harmful nonnative 
predators. This might be due to its apparent ability to forage in more 
terrestrial habitats, specifically during the vulnerable juvenile size 
classes (Rosen and Schwalbe 1988, p. 31; Rosen et al. 2001, pp. 9-10). 
In every age class, the northern Mexican gartersnake forages in aquatic 
habitats where nonnative spiny-rayed fish, bullfrogs, and crayfish are 
present, which increases not only the encounter rate between predator 
and prey, but also the juvenile mortality rate of the northern Mexican 
gartersnake, which negatively affects recruitment. As northern Mexican 
gartersnake numbers decline within a population, space becomes 
available for occupation by Marcy's checkered gartersnakes. One 
hypothesis suggests that the Marcy's checkered gartersnake might affect 
the maximum number of northern Mexican gartersnakes that an area can 
maintain based upon available resources, and could potentially 
accelerate the decline of, or preclude re-occupancy by, the northern 
Mexican gartersnake (Rosen and Schwalbe 1988, p. 31). Rosen et al. 
(2001, pp. 9-10) documented the occurrence of Marcy's checkered 
gartersnakes replacing northern Mexican gartersnakes at the San 
Bernardino National Wildlife Refuge and surrounding habitats of the 
Black Draw. Rosen and Schwalbe (1988, p. 31) report the same at the 
mouth of Potrero Canyon near its confluence with the lower Santa Cruz 
River. They suspected that drought, extending from the late 1980s 
through the late 1990s, played a role in the degree of competition for 
aquatic resources, provided an advantage to the more versatile Marcy's 
checkered gartersnake, and expedited

[[Page 41539]]

the decline of the northern Mexican gartersnake. More research is 
needed to confirm these relationships.
Mortality From Entanglement Hazards
    In addressing the effects of soil erosion associated with road 
construction projects or post-fire remedial subbasin management, 
erosion control materials placed on the ground surface are often used. 
Erosion control is considered a best management practice for most soil-
disturbing activities, and is broadly required as mitigation across the 
United States, in particular to avoid excess sedimentation of streams 
and rivers. Rolled erosion control products, such as temporary erosion 
control blankets and permanent turf reinforcement mats, are two methods 
commonly used for these purposes (Barton and Kinkead 2005, p. 34). 
These products use stitching or net-like mesh products to hold 
absorbent media together. At a restoration site in South Carolina, 19 
snakes (15 dead) representing five different species were found 
entangled in the netting and had received severe lacerations in the 
process of attempting to escape their entanglement (Barton and Kinkead 
2005, p. 34). Stuart et al. (2001, pp. 162-164) also reported the 
threats of net-like debris to snake species. Kapfer and Paloski (2011, 
p. 4) reported at least 31 instances involving six different species of 
snake (including the common gartersnake) in Wisconsin that had become 
entangled in the netting used for either erosion control or as a 
wildlife exclusion product. In their review, Kapfer and Paloski (2011, 
p. 6) noted that 0.5 in. by 0.5 in. mesh has the greatest likelihood of 
entangling snakes.
    Similar snake mortalities have not been documented in Arizona or 
New Mexico, according to our files. However, given the broad usage of 
these materials across the distribution of the northern Mexican and 
narrow-headed gartersnakes, it is not unlikely that mortality occurs 
but goes unreported. The likelihood of either gartersnake species 
becoming entangled depends on the distance these erosion control 
materials are used from water in occupied habitat and the density of 
potentially affected populations. Because erosion control products are 
usually used to prevent sedimentation of streams, there is a higher 
likelihood for gartersnakes to become entangled. This potential threat 
will require public education and additional monitoring and research, 
with emphasis in regions with occupied habitat.
    Finally, discarded fishing nets have also been documented as a 
source of mortality for northern Mexican gartersnakes in the area of 
Lake Chapala, Jalisco, Mexico (Barrag[aacute]n-Ram[iacute]rez and 
Ascencio-Arrayga 2013, p. 159). Netting or seining is not an authorized 
form of recreational fishing for sport fish in Arizona or New Mexico, 
but the practice is allowed in either state for the collection of live 
baitfish (AGFD 2013, p. 57; NMDGF 2013, p. 17). We are not certain of 
the frequency in which these techniques are used for such purposes in 
either state, but do not suspect that discarded nets or seines are 
commonly left on-site where they could ensnarl resident gartersnakes. 
However, this practice is used in Mexico as a primary means of 
obtaining freshwater fish as a food source and may be a significant 
threat to local northern Mexican gartersnake populations where this 
practice occurs.
Disease
    Our review of the scientific literature did not find evidence that 
disease is a current factor contributing to the decline in northern 
Mexican or narrow-headed gartersnakes. However, a recent wildlife 
health bulletin announced the emergence of snake fungal disease (SFD) 
within the eastern and Midwestern portions of the United States 
(Sleemen 2013, p. 1). SFD has now been diagnosed in several terrestrial 
and aquatic snake genera including Nerodia, Coluber, Pantherophis, 
Crotalus, Sistrurus, and Lampropeltis. Clinical signs of SFD include 
scabs or crusty scales, subcutaneous nodules, abnormal molting, white 
opaque cloudiness of the eyes, localized thickening or crusting of the 
skin, skin ulcers, swelling of the face, or nodules in the deeper 
tissues (Sleemen 2013, p. 1). While mortality has been documented as a 
result of SFD, population-level impacts have not, due to the cryptic 
and solitary nature of snakes and the lack of long-term monitoring data 
(Sleemen 2013, p. 1). So far, no evidence of SFD has been found in the 
genus Thamnophis but the documented occurrence of SFD in ecologically 
similar, aquatic colubrids such as Nerodia is cause for concern. We 
recommend resource managers remain diligent in looking for signs of SFD 
in wild gartersnake populations.
Summary
    We found numerous effects of livestock grazing that have resulted 
in the historical degradation of riparian and aquatic communities that 
have likely affected northern Mexican and narrow-headed gartersnakes. 
The literature concluded that mismanaged or unmanaged grazing can have 
disproportionate effects to riparian communities in arid ecosystems due 
to the attraction of livestock to water, forage, and shade. We found 
current livestock grazing activities to be more of a concern in Mexico. 
The literature is clear that the most profound impacts from livestock 
grazing in the southwestern United States occurred nearly 100 years 
ago, were significant, and may still be affecting some areas that have 
yet to fully recover. Unmanaged or poorly managed livestock operations 
likely have more pronounced effects in areas significantly impacted by 
harmful nonnative species through a reduction in cover. However, land 
managers in Arizona and New Mexico currently emphasize the protection 
of riparian and aquatic habitat in allotment management planning, 
usually through fencing, rotation, monitoring, and range improvements 
such as developing remote water sources. Collectively, these measures 
have reduced the likelihood of significant adverse impacts on northern 
Mexican or narrow-headed gartersnakes, their habitat, and their prey 
base. We also recognize that while the presence of stock tanks on the 
landscape can benefit nonnative species, well-managed stock tanks are 
an invaluable tool in the conservation and recovery of northern Mexican 
gartersnakes and their prey.
    Other activities, factors, or conditions that act in combination, 
such as road construction, use, and management, adverse human 
interactions, environmental contaminants, entanglement hazards, and 
competitive pressures from sympatric species, occur within the 
distribution of these gartersnakes and have the propensity to 
contribute to further population declines or extirpations where 
gartersnakes occur at low population densities. An emerging skin 
disease, SFD, has not yet been documented in gartersnakes but has 
affected snakes of many genera within the United States, including 
ecologically similar species, and may pose a future threat to northern 
Mexican and narrow-headed gartersnakes. Where low density populations 
are affected these types of threats described above, even the loss of a 
few reproductive adults, especially females, from a population can have 
significant population-level effects, most notably in the presence of 
harmful nonnative species. Continued population declines and 
extirpations threaten the genetic representation of each species 
because many populations have become disconnected and isolated from 
neighboring populations. This subsequently leads to a reduction in 
species redundancy and resiliency

[[Page 41540]]

when isolated, small populations are at increased vulnerability to the 
effects of stochastic events, without a means for natural 
recolonization. Based on the best available scientific and commercial 
information, we conclude these threats have the tendency to act 
synergistically and disproportionately on low-density gartersnake 
populations rangewide, now and in the foreseeable future.

The Inadequacy of Existing Regulatory Mechanisms

    Below, we examine whether existing regulatory mechanisms are 
inadequate to address the threats to the northern Mexican and narrow-
headed gartersnakes discussed under other factors. Section 4(b)(1)(A) 
of the Endangered Species Act requires the Service to take into account 
``those efforts, if any, being made by any State or foreign nation, or 
any political subdivision of a State or foreign nation, to protect such 
species.'' We interpret this language to require us to consider 
relevant Federal, State, and Tribal laws, regulations, and other such 
mechanisms that may minimize any of the threats we describe in the 
threats analysis under the other four factors, or otherwise influence 
conservation of the species. We give strongest weight to statutes and 
their implementing regulations, and management direction that stems 
from those laws and regulations. They are nondiscretionary and 
enforceable, and are considered a regulatory mechanism under this 
analysis. Having evaluated the significance of the threat as mitigated 
by any such conservation efforts, we analyze under Factor D the extent 
to which existing regulatory mechanisms are inadequate to address the 
specific threats to the species. Regulatory mechanisms, if they exist, 
may reduce or eliminate the impacts from one or more identified 
threats. In this section, we review existing State and Federal 
regulatory mechanisms to determine whether they effectively reduce or 
remove threats to the species.
    A number of Federal statutes potentially afford protection to 
northern Mexican and narrow-headed gartersnakes or their prey species. 
These include section 404 of the Clean Water Act (33 U.S.C. 1251 et 
seq.), Federal Land Policy and Management Act (43 U.S.C. 1701 et seq.), 
National Forest Management Act (16 U.S.C. 1600 et seq.), National 
Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.), and the Act. 
However, in practice, these statutes have not been able to provide 
sufficient protection to prevent the currently observed downward trend 
in northern Mexican and narrow-headed gartersnakes or their prey 
species, and the concurrent upward trend in threats.
    Section 404 of the Clean Water Act regulates placement of fill into 
waters of the United States, including the majority of northern Mexican 
and narrow-headed gartersnake habitat. However, many actions with the 
potential to be highly detrimental to both species, their prey base, 
and their habitat, such as gravel mining and irrigation diversion 
structure construction and maintenance, may be exempted from the Clean 
Water Act. Other detrimental actions, such as bank stabilization and 
road crossings, are covered under nationwide permits that receive 
limited environmental review. A lack of thorough, site-specific 
analyses for projects can allow substantial adverse effects to northern 
Mexican or narrow-headed gartersnakes, their prey base, or their 
habitat.
    The majority of the extant populations of northern Mexican and 
narrow-headed gartersnakes in the United States occur on lands managed 
by the U.S. Bureau of Land Management (BLM) and U.S. Forest Service. 
Both agencies have riparian protection goals that may provide habitat 
benefits to both species; however, neither agency has specific 
management plans for northern Mexican or narrow-headed gartersnakes. As 
a result, some of the significant threats to these gartersnakes, for 
example, those related to nonnative species, are not addressed on these 
lands. The BLM considers the northern Mexican gartersnake as a 
``Special Status Species,'' and agency biologists actively attempt to 
identify gartersnakes observed incidentally during fieldwork for their 
records (Young 2005). Otherwise, no specific protection or land-
management consideration is afforded to that species on BLM lands.
    The U.S. Forest Service does not include northern Mexican or 
narrow-headed gartersnakes on their Management Indicator Species List, 
but both species are included on the Regional Forester's Sensitive 
Species List (USFS 2007, pp. 38-39). This means they are considered in 
land management decisions, but no specific protective measures are 
conveyed to these species. Individual U.S. Forest Service biologists 
who work within the range of either northern Mexican or narrow-headed 
gartersnakes may opportunistically gather data for their records on 
gartersnakes observed incidentally in the field, although it is not 
required. The Gila National Forest mentions the narrow-headed 
gartersnake in their land and resource management plan, which includes 
standards relating to forest management for the benefit of endangered 
and threatened species as identified through approved management and 
recovery plans (CBD et al. 2011, p. 18). Neither species is mentioned 
in any other land and resource management plan for the remaining 
national forests where they occur (CBD et al. 2011, p. 18).
    The New Mexico Department of Game and Fish lists the northern 
Mexican gartersnake as State-endangered and the narrow-headed 
gartersnake as State-threatened (NMDGF 2006, Appendix H). A species is 
State-endangered if it is in jeopardy of extinction or extirpation 
within the State; a species is State-threatened if it is likely to 
become endangered within the foreseeable future throughout all or a 
significant portion of its range in New Mexico (NMDGF 2006, p. 52). 
``Take,'' defined as ``to harass, hunt, capture or kill any wildlife or 
attempt to do so'' by NMSA 17-2-38.L., is prohibited without a 
scientific collecting permit issued by the New Mexico Department of 
Game and Fish as per NMSA 17-2-41.C and New Mexico Administrative Code 
(NMAC) 19.33.6. However, while the New Mexico Department of Game and 
Fish can issue monetary penalties for illegal take of either northern 
Mexican gartersnakes or narrow-headed gartersnakes, the same provisions 
are not in place for actions that result in loss or modification of 
their habitats (NMSA 17-2-41.C and NMAC 19.33.6) (Painter 2005).
    Prior to 2005, the Arizona Game and Fish Department allowed for 
take of up to four northern Mexican or narrow-headed gartersnakes per 
person per year as specified in Commission Order 43. The Arizona Game 
and Fish Department defines ``take'' as ``pursuing, shooting, hunting, 
fishing, trapping, killing, capturing, snaring, or netting wildlife or 
the placing or using any net or other device or trap in a manner that 
may result in the capturing or killing of wildlife.'' The Arizona Game 
and Fish Department subsequently amended Commission Order 43, effective 
January 2005. Take of northern Mexican and narrow-headed gartersnakes 
is no longer permitted in Arizona without issuance of a scientific 
collecting permit (Ariz. Admin. Code R12-4-401 et seq.), or special 
authorization. While the Arizona Game and Fish Department can seek 
criminal or civil penalties for illegal take of these species, the same 
provisions are not in place for actions that result in destruction or 
modification of the gartersnakes' habitat. In addition to making the 
necessary regulatory changes to promote the conservation of northern 
Mexican and narrow-headed gartersnakes, the

[[Page 41541]]

Arizona Game and Fish Departments' Nongame Branch continues to be a 
strong partner in research and survey efforts that further our 
understanding of current populations, and assist with conservation 
efforts and the establishment of long-term conservation partnerships.
    Throughout Mexico, the Mexican gartersnake is listed at the species 
level of its taxonomy as ``Amenazadas,'' or Threatened, by the 
Secretaria de Medio Ambiente y Recursos Naturales (SEMARNAT) (SEDESOL 
2001). Threatened species are ``those species, or populations of the 
same, likely to be in danger of disappearing in a short or medium 
timeframe, if the factors that negatively impact their viability, cause 
the deterioration or modification of their habitat or directly diminish 
the size of their populations continue to operate'' (SEDESOL 2001 (NOM-
059-ECOL-2001), p. 4). This designation prohibits taking of the 
species, unless specifically permitted, as well as prohibits any 
activity that intentionally destroys or adversely modifies its habitat 
(SEDESOL 2000 (LGVS) and 2001 (NOM-059-ECOL-2001)). Additionally, in 
1988, the Mexican Government passed a regulation that is similar to the 
National Environmental Policy Act of the United States. This Mexican 
regulation requires an environmental assessment of private or 
government actions that may affect wildlife or their habitat (SEDESOL 
1988 (LGEEPA)).
    The Mexican Federal agency known as the Instituto Nacional de 
Ecolog[iacute]a (INE) is responsible for the analysis of the status and 
threats that pertain to species that are proposed for listing in the 
Norma Oficial Mexicana NOM-059 (the Mexican equivalent to an endangered 
and threatened species list), and, if appropriate, the nomination of 
species to the list. INE is generally considered the Mexican 
counterpart to the United States' Fish and Wildlife Service. INE 
developed the Method of Evaluation of the Risk of Extinction of the 
Wild Species in Mexico (MER), which unifies the criteria of decisions 
on the categories of risk and permits the use of specific information 
fundamental to listing decisions. The MER is based on four independent, 
quantitative criteria: (1) Size of the distribution of the taxon in 
Mexico; (2) state (quality) of the habitat with respect to natural 
development of the taxon; (3) intrinsic biological vulnerability of the 
taxon; and (4) impacts of human activity on the taxon. INE began to use 
the MER in 2006; therefore, all species previously listed in the NOM-
059 were based solely on expert review and opinion in many cases. 
Specifically, until 2006, the listing process under INE consisted of a 
panel of scientific experts who convened as necessary for the purpose 
of defining and assessing the status and threats that affect Mexico's 
native species that are considered to be at risk, and applying those 
factors to the definitions of the various listing categories. In 1994, 
when the Mexican gartersnake was placed on the NOM-059 (SEDESOL 1994 
(NOM-059-ECOL-1994), p. 46) as a threatened species, the decision was 
made by a panel of scientific experts.
    Although the Mexican gartersnake is listed as a threatened species 
in Mexico and based on our experience collaborating with Mexico on 
transborder conservation efforts, no recovery plan or other 
conservation planning occurs because of this status and enforcement of 
the regulation protecting the gartersnake is sporadic, depending on 
available resources and location. Based upon the best available 
scientific and commercial information on the status of the species, and 
the historic and continuing threats to its habitat in Mexico, our 
analysis concludes that regulatory mechanisms enacted by the Mexican 
government to conserve the northern Mexican gartersnake are not 
adequate to address threats to the species or its habitat.
    In summary, there are a number of existing regulations that 
potentially address issues affecting the northern Mexican and narrow-
headed gartersnakes and their habitats. However, existing regulations 
within the range of northern Mexican and narrow-headed gartersnakes 
typically only address the direct take of individuals without a permit, 
and provide little, if any, protection of gartersnake habitat. Arizona 
and New Mexico statutes do not provide protection of habitat and 
ecosystems. Legislation in Mexico prohibits intentional destruction or 
modification of northern Mexican gartersnake habitat, but neither that, 
nor prohibitions of take, appear to be adequate to address ongoing 
threats.

Current Conservation of Northern Mexican and Narrow-Headed Gartersnakes

    Several conservation measures implemented by land and resource 
managers, private land owners, and other stakeholders can directly or 
indirectly benefit populations of northern Mexican and narrow-headed 
gartersnakes. For example, the AGFD's conservation and mitigation 
program (implemented under an existing section 7 incidental take 
permit) has committed to either stocking (with captive bred stock) or 
securing two populations each of northern Mexican and narrow-headed 
gartersnakes to help minimize adverse effects to these species from 
their sport fish stocking program through 2021 (USFWS 2011, Appendix 
C). However, to achieve these goals, challenges must be overcome. 
First, captive propagation of both gartersnake species remains 
problematic. After approximately 5 years of experimentation with 
captive propagation at five institutions, using two colonies of 
northern Mexican gartersnakes and three colonies of narrow-headed 
gartersnakes, success has been limited (see GCWG 2007, 2008, 2009, 
2010). In 2012, approximately 40 northern Mexican gartersnakes were 
produced at one institution, and they were subsequently marked and 
released along Cienega Creek. These were the first gartersnakes of 
either species to be produced under this program, but their current 
status in the wild remains unknown. No narrow-headed gartersnakes have 
been produced in captivity under this program since its inception. 
Secondly, in order to be successful, the process of ``securing'' a 
population of either species will likely involve an aggressive 
nonnative removal strategy, and will have to account for habitat 
connectivity to prevent reinvasion of unwanted species. Therefore, 
securing a population of either species may involve removal of harmful 
nonnatives from an entire subbasin.
    To improve the status of northern Mexican gartersnakes in this 
subbasin, the AGFD recently purchased the approximate 200-acre (81-ha) 
Horseshoe Ranch along the Agua Fria River located near the Bloody Basin 
Road crossing, east of Interstate 17 and southeast of Cordes Junction, 
Arizona. The AGFD plans to introduce northern Mexican gartersnakes as 
well as lowland leopard frogs and native fish species into a large 
pond, protected by bullfrog exclusion fencing, located adjacent to the 
Agua Fria River. The bullfrog exclusion fencing around the pond will 
permit the dispersal of northern Mexican gartersnakes and lowland 
leopard frogs from the pond, allowing the pond to act as a source 
population to the Agua Fria River. The AGFD's short- to mid-term 
conservation planning for Horseshoe Ranch will help ensure the northern 
Mexican gartersnake persists in this historical stronghold.
    In 2007, the New Mexico Department of Game and Fish completed a 
recovery plan for narrow-headed gartersnakes in New Mexico (Pierce 
2007, pp. 13-15) that included the following management objectives: (1) 
Researching the effect of known threats to, and natural history of,

[[Page 41542]]

the species; (2) acquiring funding sources for research, monitoring, 
and management; (3) enhancing education and outreach; and (4) managing 
against known threats to the species. Implementation of the recovery 
plan was to occur between the second half of 2007 through 2011, and was 
divided into three main categories: (1) Improve and maintain knowledge 
of potential threats to the narrow-headed gartersnake; (2) improve and 
maintain knowledge of the biology of the narrow-headed gartersnake; and 
(3) develop and maintain high levels of cooperation and coordination 
between stakeholders and interested parties (Pierce 2007, pp. 16-17). 
Our review of the plan found that it lacked specific threat-mitigation 
commitments on the landscape, as well as stakeholder accountability for 
implementing activities prescribed in the plan. We also found that 
actions calling for targeted nonnative species removal or management 
were absent in the implementation schedule provided in Pierce (2007; p. 
17). As we have discussed at length, harmful nonnative species are the 
primary driver of continued declines in both gartersnake species. No 
recovery plan, conservation plan, or conservation agreement currently 
exists in New Mexico with regard to the northern Mexican gartersnake 
(NMDGF 2006, Table 6-3).
    Both northern Mexican and narrow-headed gartersnakes are considered 
``Candidate Species'' in the Arizona Game and Fish Department draft 
document, Wildlife of Special Concern (WSCA) (AGFD In Prep., p. 12). A 
``Candidate Species'' is one ``whose threats are known or suspected but 
for which substantial population declines from historical levels have 
not been documented (though they appear to have occurred)'' (AGFD In 
Prep., p. 12). The purpose of the WSCA list is to provide guidance in 
habitat management implemented by land-management agencies. 
Additionally, both northern Mexican and narrow-headed gartersnakes are 
considered a ``Tier 1b Species of Greatest Conservation Need (SGCN)'' 
in the Arizona Game and Fish Department document, Arizona's 
Comprehensive Wildlife Conservation Strategy (CWCS) (AGFD 2006a, pp. 
499-501). The purpose for the CWCS is to ``provide an essential 
foundation for the future of wildlife conservation and a stimulus to 
engage the States, federal agencies, and other conservation partners to 
strategically think about their individual and coordinated roles in 
prioritizing conservation efforts'' (AGFD 2006a, p. 2). A ``Tier 1b 
SGCN'' is one that requires immediate conservation actions aimed at 
improving conditions through intervention at the population or habitat 
level (AGFD 2006a, p. 32). In the 2011 draft revised State wildlife 
action plan (an updated version of the CWCS), northern Mexican 
gartersnake is a Tier 1a SGCN. Tier 1a species ``comprise a large 
percentage of [AGFD's] management resource allocation'' and ``are 
[their] highest priorities.'' Neither the WSCA nor the CWCS are 
regulatory documents and, consequently, do not provide and specific 
protections for either the gartersnakes themselves, or their habitats. 
The Arizona Game and Fish Department does not have specified or 
mandated recovery goals for either the northern Mexican or narrow-
headed gartersnake, nor has a conservation agreement or recovery plan 
been developed for either species.
    Indirect benefits for both gartersnake species occur through 
recovery actions designed for their prey species. Since the Chiricahua 
leopard frog was listed as threatened under the Act, significant 
strides have been made in its recovery, and the mitigation of its known 
threats. The northern Mexican gartersnake, in particular, has likely 
benefitted from these actions, at least in some areas, such as at the 
Las Cienegas Natural Conservation Area and in Scotia Canyon of the 
Huachuca Mountains. However, much of the recovery of the Chiricahua 
leopard frog has occurred in areas that have not directly benefitted 
the northern Mexican gartersnake, either because these activities have 
occurred outside the known distribution of the northern Mexican 
gartersnake or because they have occurred in isolated lentic systems 
that are far removed from large perennial streams that typically 
provide source populations of northern Mexican gartersnakes. In recent 
years, significant strides have been made in controlling bullfrogs on 
local landscape levels in Arizona, such as in the Scotia Canyon area, 
in the Las Cienegas National Conservation Area, on the BANWR, and in 
the vicinity of Pena Blanca Lake in the Pajarito Mountains. Recent 
efforts to return the Las Cienegas National Conservation Area to a 
wholly native biological community have involved bullfrog eradication 
efforts, as well as efforts to recover the Chiricahua leopard frog and 
native fish species. These actions should assist in conserving the 
northern Mexican gartersnake population in this area. Bullfrog control 
has been shown to be most effective in simple, lentic systems such as 
stock tanks. Therefore, we encourage livestock managers to work with 
resource managers in the systematic eradication of bullfrogs from stock 
tanks where they occur, or at a minimum, ensure they are never 
introduced.
    An emphasis on native fish recovery in fisheries management and 
enhanced nonnative species control to favor native communities may be 
the single most efficient and effective manner to recover these 
gartersnakes, in addition to all listed or sensitive native fish and 
amphibian species which they prey upon. Alternatively, resource 
management policies that either directly benefit or maintain nonnative 
community assemblages to the exclusion of native species are likely to 
significantly reduce the potential for the conservation and recovery of 
northern Mexican and narrow-headed gartersnakes.
    Fisheries managers strive to balance the needs of the recreational 
angling community against those required by native aquatic communities. 
Fisheries management has direct implications for the conservation and 
recovery of northern Mexican and narrow-headed gartersnakes in the 
United States. Clarkson et al. (2005) discuss management conflicts as a 
primary factor in the decline of native fish species in the 
southwestern United States, and declare the entire native fish fauna as 
imperiled. The investigators cite nonnative species as the most 
consequential factor leading to rangewide declines of native fish, and 
that such declines prevent or negate species' recovery efforts from 
being implemented or being successful (Clarkson et al. 2005, p. 20). 
Maintaining the status quo of current management of fisheries within 
the southwestern United States will have serious adverse effects to 
native fish species (Clarkson et al. 2005, p. 25), which will affect 
the long-term viability of northern Mexican and narrow-headed 
gartersnakes and their potential for recovery. Clarkson et al. (2005, 
p. 20) also note that over 50 nonnative species have been introduced 
into the Southwest as either sportfish or baitfish, and some are still 
being actively stocked, managed for, and promoted by both Federal and 
State agencies as nonnative recreational fisheries.
    To help resolve the fundamental conflict of management between 
native fish and recreational sport fisheries, Clarkson et al. (2005, 
pp. 22-25) propose the designation of entire subbasins as having either 
native or nonnative fisheries and manage for these goals aggressively. 
The idea of watershed-segregated fisheries management is also supported 
by Marsh and Pacey (2005, p. 62). As part of the Arizona Game and Fish 
Department's

[[Page 41543]]

overall wildlife conservation strategy, the AGFD has planned an 
integrated fisheries management approach (AGFD 2006a, p. 349), which is 
apparently designed to manage subbasins specifically for either 
nonnative or native fish communities. The AGFD has not yet decided how 
fisheries will be managed in Arizona's subbasins. However, angler 
access, existing fish communities, and stream flow considerations are 
likely to inform such broadly based decisions. Several of Arizona's 
large perennial rivers present an array of existing sport fishing 
opportunities and access points, contain harmful nonnative fish 
species, and also serve as important habitat for either northern 
Mexican or narrow-headed gartersnakes. These rivers may be targeted 
though this planning exercise for nonnative fisheries management, which 
would likely remove any recovery potential for gartersnakes in these 
areas, and, perhaps, even result in the local extirpations of 
populations of northern Mexican and narrow-headed gartersnakes. 
Alternatively, subbasins that are targeted for wholly native species 
assemblages would likely secure the persistence of northern Mexican and 
narrow-headed gartersnakes that occur there, if not result in their 
complete recovery in these areas. Specific subbasins where targeted 
fisheries management is to occur were not provided in AGFD (2006a), but 
depending on which areas are chosen for each management emphasis, the 
potential for future conservation and recovery of northern Mexican and 
narrow-headed gartersnakes could either be significantly bolstered, or 
significantly hampered. Close coordination with the Arizona Game and 
Fish Department on the delineation of fisheries management priorities 
in Arizona's subbasins will be instrumental to ensuring that 
conservation and recovery of northern Mexican and narrow-headed 
gartersnakes can occur.
    Conservation of these gartersnakes has been implemented in the 
scientific and management communities as well. The AGFD recently 
produced identification cards for distribution that provide information 
to assist field professionals with the identification of each of 
Arizona's five native gartersnake species, as well as guidance on 
submitting photographic vouchers for university museum collections. 
Arizona State University and the University of Arizona now accept 
photographic vouchers in lieu of physical specimens, in their 
respective museum collections. These measures appreciably reduce the 
necessity for physical specimens (unless discovered postmortem) for 
locality voucher purposes and, therefore, further reduce impacts to 
vulnerable populations of northern Mexican or narrow-headed 
gartersnakes.
    Despite these collective efforts we have described above, northern 
Mexican and narrow-headed gartersnakes have continued to decline 
throughout their ranges.

Proposed Determination

    In our review of the best available science, we found that aquatic 
ecosystems which northern Mexican and narrow-headed gartersnakes rely 
on and are part of have been significantly compromised by harmful 
nonnative species. We found this threat to be the most significant and 
pervasive of all threats affecting both species. Harmful nonnative 
species have been intentionally released or have naturally moved into 
virtually every subbasin throughout the range of the northern Mexican 
and narrow-headed gartersnakes. This has resulted in widespread 
declines in native fish and amphibian communities, which are integral 
to the continued survival of the northern Mexican and narrow-headed 
gartersnakes. In addition to widespread competitive pressures, harmful 
nonnative species have directly impacted both gartersnake species 
through predation. In combination, these factors have resulted in 
widespread population declines and extirpations in both species, as 
neither gartersnake nor their prey evolved in their presence.
    In addition to the declining status of the biotic communities where 
the northern Mexican and narrow-headed gartersnakes occur, land use 
activities, drought, and wildfires threaten vital elements of their 
habitat that are important for their survival. Dams, diversions, flood-
control projects, and groundwater pumping have dewatered entire reaches 
of historically occupied habitat for both species, rangewide. Large 
dams planned in the future threaten to dewater additional reaches. 
Climate change predictions include increased aridity, lower annual 
precipitation totals, lower snow pack levels, higher variability in 
flows (lower low-flows and higher high-flows), and enhanced stress on 
ponderosa pine communities in the southwestern United States and 
northern Mexico. Increasing water demands from a rapidly growing human 
population in the arid southwestern United States, combined with a 
drought-limited supply of surface water, fuels future needs for even 
more dams, diversions, and groundwater pumping. Due in part to the fire 
management policies of recent decades, wildfires in the arid 
southwestern United States have grown more frequent and severe. Since 
2011, both Arizona and New Mexico experienced the largest wildfires in 
their respective State histories. High-intensity wildfires that affect 
large areas contribute to significant flooding and sedimentation, 
resulting in fish kills and the filling-in of important pool habitat. 
These conditions remove a portion of, or the entire prey base, for 
northern Mexican and narrow-headed gartersnakes for extended periods of 
time. This scenario places significant stress on resident gartersnake 
populations through starvation.
    Other activities, factors, or conditions that act in combination, 
such as mismanaged or unmanaged livestock grazing; road construction, 
use, and management; adverse human interactions; environmental 
contaminants; erosion control techniques; and competitive pressures 
from sympatric species, occur within the distribution of these 
gartersnakes and have the tendency to contribute to further population 
declines or extirpations where gartersnakes occur at low population 
densities. In the presence of harmful nonnative species, the negative 
effects of these threats on northern Mexican and narrow-headed 
gartersnakes are amplified. Yet, there are currently no regulatory 
mechanisms in place to address the threats to these species that 
specifically target the conservation of northern Mexican or narrow-
headed gartersnakes or their habitat in the United States or Mexico.
    Collectively, the ubiquitous nature of these threats across the 
landscape has appreciably reduced the quality and quantity of suitable 
gartersnake habitat and changed its spatial orientation on the 
landscape. This ultimately renders populations much less resilient to 
stochastic, natural, or anthropogenic stressors that could otherwise be 
withstood. Over time and space, subsequent population declines have 
threatened the genetic representation of each species because many 
populations have become disconnected and isolated from neighboring 
populations. Expanding distances between extant populations coupled 
with threats that prevent normal recolonizing mechanisms leave existing 
populations vulnerable to extirpation. This subsequently leads to a 
reduction in species redundancy when isolated, small populations are at 
increased vulnerability to the effects of stochastic events, without a 
means for natural recolonization. Ultimately, the effect of

[[Page 41544]]

scattered, small, and disjunct populations, without the means to 
naturally recolonize, is weakened species resiliency as a whole, which 
ultimately enhances the risk of the species becoming endangered.
    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We have carefully assessed the best 
scientific and commercial information available regarding the past, 
present, and future threats to the species, and have determined that 
the northern Mexican gartersnake and narrow-headed gartersnake both 
meet the definition of a threatened species under the Act. Significant 
threats are occurring now and are likely to continue in the foreseeable 
future, at a high intensity, and across these species' entire ranges; 
therefore, we have determined these species are likely to become 
endangered throughout all or a significant portion of their ranges 
within the foreseeable future. Because these threats are likely to 
cause these gartersnakes to become endangered throughout all or a 
significant portion of their ranges within the foreseeable future, we 
find these species are threatened, not endangered. Therefore, on the 
basis of the best available scientific and commercial information, we 
propose listing the northern Mexican gartersnake and narrow-headed 
gartersnake as threatened species in accordance with sections 3(20) and 
4(a)(1) of the Act. The current status of the northern Mexican and 
narrow-headed gartersnakes meets the definition of threatened, not 
endangered, because while we found numerous threats to be significant 
and rangewide, our available survey data conclude that the remaining 
small number of populations are viable. Alternatively and based upon 
the data available, the northern Mexican and narrow-headed gartersnakes 
appear to remain extant, as low-density populations with the threat of 
extirpation, in most subbasins where they historically occurred.

Special Rule for Northern Mexican Gartersnake Under Section 4(d) of the 
Act

    Whenever a species is listed as a threatened species under the Act, 
the Secretary may specify regulations that she deems necessary and 
advisable to provide for the conservation of that species under the 
authorization of section 4(d) of the Act. These rules, commonly 
referred to as ``special rules,'' are found in part 17 of title 50 of 
the Code of Federal Regulations (CFR) in Sec. Sec.  17.40-17.48. This 
proposed special rule for Sec.  17.42 would exempt take of northern 
Mexican gartersnakes as a result of livestock use at or maintenance 
activities of livestock tanks located on private, State, or Tribal 
lands.
    The proposed special rule would replace the Act's general 
prohibitions against take of the northern Mexican gartersnake with 
special measures tailored to the conservation of the species on all 
non-Federal lands. Through the maintenance and operation of the stock 
tanks for cattle, habitat is provided for the northern Mexican 
gartersnake and numerous prey species; hence there is a conservation 
benefit to the species. Under the proposed special rule, take of 
northern Mexican gartersnake caused by livestock use of or maintenance 
activities at livestock tanks located on private, State, or Tribal 
lands would be exempt from section 9 of the Act. A livestock tank is 
defined as an existing or future impoundment in an ephemeral drainage 
or upland site constructed primarily as a watering site for livestock. 
The proposed special rule targets tanks on private, State, and Tribal 
lands to encourage landowners and ranchers to continue to maintain 
these tanks as they provide habitat for the northern Mexican 
gartersnake. Livestock use and maintenance of tanks on Federal lands 
would be addressed through the section 7 process. When a Federal 
action, such as permitting livestock grazing on Federal lands, may 
affect a listed species, consultation between us and the action agency 
is required under section 7 of the Act. The conclusion of consultation 
may include mandatory changes in livestock programs in the form of 
measures to minimize take of a listed animal or to avoid jeopardizing 
the continued existence of a listed species. Changes in a proposed 
action resulting from consultations are almost always minor.

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
practices. Recognition through listing results in public awareness and 
conservation by Federal, State, Tribal, and local agencies, private 
organizations, and individuals. The Act encourages cooperation with the 
States and requires that recovery actions be carried out for all listed 
species. The protection required by Federal agencies and the 
prohibitions against certain activities are discussed, in part, below.
    The primary purpose of the Act is the conservation of endangered 
and threatened species and the ecosystems upon which they depend. The 
ultimate goal of such conservation efforts is the recovery of these 
listed species, so that they no longer need the protective measures of 
the Act. Subsection 4(f) of the Act requires the Service to develop and 
implement recovery plans for the conservation of endangered and 
threatened species. The recovery planning process involves the 
identification of actions that are necessary to halt or reverse the 
species' decline by addressing the threats to its survival and 
recovery. The goal of this process is to restore listed species to a 
point where they are secure, self-sustaining, and functioning 
components of their ecosystems.
    Recovery planning includes the development of a recovery outline 
shortly after a species is listed, preparation of a draft and final 
recovery plan, and revisions to the plan as significant new information 
becomes available. The recovery outline guides the immediate 
implementation of urgent recovery actions and describes the process to 
be used to develop a recovery plan. The recovery plan identifies site-
specific management actions that will achieve recovery of the species, 
measurable criteria that determine when a species may be downlisted or 
delisted, and methods for monitoring recovery progress. Recovery plans 
also establish a framework for agencies to coordinate their recovery 
efforts and provide estimates of the cost of implementing recovery 
tasks. Recovery teams (comprised of species experts, Federal and State 
agencies, nongovernment organizations, and stakeholders) are often 
established to develop recovery plans. When completed, the recovery 
outline, draft recovery plan, and the final recovery plan will be 
available on our Web site (http://www.fws.gov/endangered), or from our 
Arizona Ecological Services Field Office (see FOR FURTHER INFORMATION 
CONTACT).
    Implementation of recovery actions generally requires the 
participation of a broad range of partners, including other Federal 
agencies, States, Tribal, nongovernmental organizations, businesses, 
and private landowners. Examples of recovery actions include habitat 
restoration (e.g., restoration of native vegetation), research, captive 
propagation and reintroduction, and outreach and education. The 
recovery of many listed species cannot be accomplished solely on 
Federal lands because their range may occur primarily

[[Page 41545]]

or solely on non-Federal lands. To achieve recovery of these species 
requires cooperative conservation efforts on private, State, and Tribal 
lands.
    If these species are listed, funding for recovery actions will be 
available from a variety of sources, including Federal budgets, State 
programs, and cost share grants for non-Federal landowners, the 
academic community, and nongovernmental organizations. In addition, 
under section 6 of the Act, the States of Arizona and New Mexico would 
be eligible for Federal funds to implement management actions that 
promote the protection and recovery of the northern Mexican and narrow-
headed gartersnakes. Information on our grant programs that are 
available to aid species recovery can be found at: http://www.fws.gov/grants.
    Although the northern Mexican and narrow-headed gartersnakes are 
only proposed for listing under the Act at this time, please let us 
know if you are interested in participating in recovery efforts for 
this species. Additionally, we invite you to submit any new information 
on these species whenever it becomes available and any information you 
may have for recovery planning purposes (see FOR FURTHER INFORMATION 
CONTACT).
    Section 7(a) of the Act requires Federal agencies to evaluate their 
actions with respect to any species that is proposed or listed as 
endangered or threatened and with respect to its critical habitat, if 
any is designated. Regulations implementing this interagency 
cooperation provision of the Act are codified at 50 CFR part 402. 
Section 7(a)(4) of the Act requires Federal agencies to confer with the 
Service on any action that is likely to jeopardize the continued 
existence of a species proposed for listing or result in destruction or 
adverse modification of proposed critical habitat. If a species is 
listed subsequently, section 7(a)(2) of the Act requires Federal 
agencies to ensure that activities they authorize, fund, or carry out 
are not likely to jeopardize the continued existence of the species or 
destroy or adversely modify its critical habitat. If a Federal action 
may affect a listed species or its critical habitat, the responsible 
Federal agency must enter into formal consultation with the Service.
    Federal agency actions within the species' habitats that may 
require conference or consultation or both as described in the 
preceding paragraph include management and any other landscape altering 
activities on Federal lands administered by the Fish and Wildlife 
Service, U.S. Bureau of Reclamation, or U.S. Forest Service; issuance 
of section 404 Clean Water Act permits by the U.S. Army Corps of 
Engineers; construction and management of gas pipeline and power line 
rights-of-way by the Federal Energy Regulatory Commission; construction 
and maintenance of roads or highways by the Federal Highway 
Administration; and other discretionary actions that effect the species 
composition of biotic communities where these species or their habitats 
occur, such as funding or permitting programs that result in the 
continued stocking of nonnative, spiny-rayed fish.
    The Act and its implementing regulations set forth a series of 
general prohibitions and exceptions that apply to all endangered 
wildlife. The prohibitions of section 9(a)(2) of the Act, codified at 
50 CFR 17.21 for endangered wildlife, in part, make it illegal for any 
person subject to the jurisdiction of the United States to take 
(includes harass, harm, pursue, hunt, shoot, wound, kill, trap, 
capture, or collect; or to attempt any of these), import, export, ship 
in interstate commerce in the course of commercial activity, or sell or 
offer for sale in interstate or foreign commerce any listed species. 
Under the Lacey Act (18 U.S.C. 42-43; 16 U.S.C. 3371-3378), it is also 
illegal to possess, sell, deliver, carry, transport, or ship any such 
wildlife that has been taken illegally. Certain exceptions apply to 
agents of the Service and State conservation agencies. The prohibitions 
of section 9(a)(2) of the Act, codified at CFR 17.31 for threatened 
wildlife, make it such that all the provisions of 50 CFR 17.21 apply, 
except Sec.  17.21(c)(5).
    We may issue permits to carry out otherwise prohibited activities 
involving endangered and threatened wildlife species under certain 
circumstances. Regulations governing permits are codified at 50 CFR 
17.22 for endangered species, and at 17.32 for threatened species. A 
permit must be issued for the following purposes: for scientific 
purposes, to enhance the propagation or survival of the species, and 
for incidental take in connection with otherwise lawful activities.
    It is our policy, as published in the Federal Register on July 1, 
1994 (59 FR 34272), to identify to the maximum extent practicable at 
the time a species is listed, those activities that would or would not 
constitute a violation of section 9 of the Act. The intent of this 
policy is to increase public awareness of the effect of a proposed 
listing on proposed and ongoing activities within the range of species 
proposed for listing. The following activities could potentially result 
in a violation of section 9 of the Act; this list is not comprehensive:
    (1) Unauthorized collecting, handling, possessing, selling, 
delivering, carrying, or transporting of the species, including import 
or export across State lines and international boundaries, except for 
properly documented antique specimens of these taxa at least 100 years 
old, as defined by section 10(h)(1) of the Act;
    (2) The unauthorized introduction of harmful nonnative species that 
compete with or prey upon northern Mexican and narrow-headed 
gartersnakes, such as the stocking of nonnative, spiny-rayed fish, or 
illegal transport, use, or release of bullfrogs or crayfish in the 
States of Arizona and New Mexico;
    (3) The unauthorized release of biological control agents that 
attack any age class of northern Mexican and narrow-headed gartersnakes 
or any life stage of their prey species;
    (4) Unauthorized modification of the channel, reduction or 
elimination of water flow of any stream or water body, or the complete 
removal or significant destruction of riparian vegetation associated 
with occupied northern Mexican or narrow-headed gartersnake habitat; 
and
    (5) Unauthorized discharge of chemicals or fill material into any 
waters in which northern Mexican and narrow-headed gartersnakes are 
known to occur.
    Questions regarding whether specific activities would constitute a 
violation of section 9 of the Act should be directed to the Arizona 
Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT). 
Requests for copies of the regulations concerning listed animals and 
general inquiries regarding prohibitions and permits may be addressed 
to the U.S. Fish and Wildlife Service, Endangered Species Permits, P.O. 
Box 1306, Albuquerque, New Mexico 87103 (telephone (505) 248-6920, 
facsimile (505) 248-6922).

Peer Review

    In accordance with our joint policy on peer review published in the 
Federal Register on July 1, 1994 (59 FR 34270), we will seek the expert 
opinions of at least three appropriate and independent specialists 
regarding this proposed rule. The purpose of peer review is to ensure 
that our listing determination is based on scientifically sound data, 
assumptions, and analyses. We have invited these peer reviewers to 
comment during this public comment period on our specific assumptions 
and conclusions in this proposed listing determination.

[[Page 41546]]

    We will consider all comments and information received during this 
comment period on this proposed rule during our preparation of a final 
determination. Accordingly, the final decision may differ from this 
proposal.

Public Hearings

    Section 4(b)(5) of the Act provides for one or more public hearings 
on this proposal, if requested. Requests must be received within 45 
days after the date of publication of this proposed rule in the Federal 
Register. Such requests must be sent to the address shown in the FOR 
FURTHER INFORMATION CONTACT section. We will schedule public hearings 
on this proposal, if any are requested, and announce the dates, times, 
and places of those hearings, as well as how to obtain reasonable 
accommodations, in the Federal Register and local newspapers at least 
15 days before the hearing.

Required Determinations

Clarity of the Rule

    We are required by Executive Orders 12866 and 12988 and by the 
Presidential Memorandum of June 1, 1998, to write all rules in plain 
language. This means that each rule we publish must:
    (1) Be logically organized;
    (2) Use the active voice to address readers directly;
    (3) Use clear language rather than jargon;
    (4) Be divided into short sections and sentences; and
    (5) Use lists and tables wherever possible.
    If you feel that we have not met these requirements, send us 
comments by one of the methods listed in the ADDRESSES section. To 
better help us revise the rule, your comments should be as specific as 
possible. For example, you should tell us the numbers of the sections 
or paragraphs that are unclearly written, which sections or sentences 
are too long, the sections where you feel lists or tables would be 
useful, etc.

National Environmental Policy Act (42 U.S.C. 4321 et seq.)

    We have determined that environmental assessments and environmental 
impact statements, as defined under the authority of the National 
Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.), need not be 
prepared in connection with listing a species as an endangered or 
threatened species under the Endangered Species Act. We published a 
notice outlining our reasons for this determination in the Federal 
Register on October 25, 1983 (48 FR 49244).

References Cited

    A complete list of references cited in this rulemaking is available 
on the Internet at http://www.regulations.gov and upon request from the 
Arizona Ecological Services Field Office (see FOR FURTHER INFORMATION 
CONTACT).

Authors

    The primary authors of this proposed rule are the staff members of 
the Arizona Ecological Services Field Office.

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, Transportation.

Proposed Regulation Promulgation

    Accordingly, we propose to amend part 17, subchapter B of chapter 
I, title 50 of the Code of Federal Regulations, as set forth below:

PART 17--[AMENDED]

0
1. The authority citation for part 17 continues to read as follows:

    Authority:  16 U.S.C. 1361-1407; 1531-1544; and 4201-4245, 
unless otherwise noted.

0
2. In Sec.  17.11(h), add entries for ``Gartersnake, northern Mexican'' 
and ``Gartersnake, narrow-headed'' to the List of Endangered and 
Threatened Wildlife in alphabetical order under REPTILES to read as 
follows:


Sec.  17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------
                        Species                                                    Vertebrate
--------------------------------------------------------                        population where                                  Critical     Special
                                                            Historic range       endangered or         Status      When listed    habitat       rules
           Common name                Scientific name                              threatened
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
                                                                      * * * * * * *
             REPTILES
 
                                                                      * * * * * * *
Gartersnake, northern Mexican....  Thamnophis eques      U.S.A. (AZ, NM),     Entire.............  T.............  ...........     17.95(d)     17.42(g)
                                    megalops.             Mexico.
 
                                                                      * * * * * * *
Gartersnake, narrow-headed.......  Thamnophis            U.S.A. (AZ, NM)....  Entire.............  T.............  ...........     17.95(d)           NA
                                    rufipunctatus.
 
                                                                      * * * * * * *
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0
3. Amend Sec.  17.42 by adding a new paragraph (g) to read as follows:


Sec.  17.42  Special rules--reptiles.

* * * * *
    (g) Northern Mexican gartersnake (Thamnophis eques megalops)--(1) 
Which populations of the northern Mexican gartersnake are covered by 
this special rule? This rule covers the distribution of this species in 
the contiguous United States.
    (2) What activities are prohibited? Any activity where northern 
Mexican gartersnakes are attempted to be, or are intended to be, 
trapped, hunted, shot, or collected, in the contiguous United States, 
is prohibited. It is also prohibited to incidentally trap, shoot, 
capture, pursue, or collect northern Mexican gartersnakes in the course 
of otherwise legal activities.
    (3) What activities are allowed? Incidental take of northern 
Mexican gartersnakes is not a violation of section 9 of the Act if it 
occurs from any other otherwise legal activities involving northern 
Mexican gartersnakes and their habitat that are conducted in accordance 
with applicable State, Federal, tribal, and local laws and regulations. 
Such activities occurring in northern Mexican gartersnake habitat 
include maintenance

[[Page 41547]]

activities at livestock tanks located on private, State, or Tribal 
lands. A livestock tank is an existing or future impoundment in an 
ephemeral drainage or upland site constructed primarily as a watering 
site for livestock.
* * * * *

    Dated: June 24, 2013.
Daniel M. Ashe,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2013-16521 Filed 7-9-13; 8:45 am]
BILLING CODE 4310-55-P