[Federal Register Volume 62, Number 135 (Tuesday, July 15, 1997)]
[Proposed Rules]
[Pages 37852-37860]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-18688]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AC10


Endangered and Threatened Wildlife and Plants; Withdrawal of the 
Proposed Rule To List the Flat-Tailed Horned Lizard as Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; withdrawal.

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SUMMARY: The U.S. Fish and Wildlife Service (Service) withdraws the 
proposed rule to list the flat-tailed horned lizard (Phrynosoma 
mcallii) as threatened, pursuant to the Endangered Species Act of 1973, 
as amended (Act). The Service is taking this action because some of the 
threats are less serious than at the time the proposed rule was 
published, a conservation agreement will ensure further reductions in 
threats, and data indicating a population decline are inconclusive. The 
Service will continue to monitor the status of this species and work 
with involved interests for conservation of the species.

ADDRESSES: The complete file for this rule is available for inspection, 
by appointment, during normal business hours at the Carlsbad Ecological 
Services Field Office, U.S. Fish and Wildlife Service, 2730 Loker 
Avenue West, Carlsbad, California, 92008.

FOR FURTHER INFORMATION CONTACT: Sandy Vissman, at the above address or 
by telephone at (760) 431-9440.

SUPPLEMENTARY INFORMATION:

Background

    The flat-tailed horned lizard (Phrynosoma mcallii) is a small, 
cryptically colored, phrynosomatid lizard that reaches a maximum adult 
body length (excluding the tail) of approximately 81 millimeters (3.2 
inches). The lizard has a flattened body, short tail, and dagger-like 
head spines like other horned lizards. It is distinguished from other 
horned lizards in its range by a dark vertebral stripe, two slender 
elongated occipital spines, and the absence of external ear openings. 
The dorsal surface of the flat-tailed horned lizard is pale gray to 
light rusty brown. The ventral surface is white and unmarked, with the 
exception of a prominent umbilical scar.
    The lizard was first collected by Colonel G.A. M'Call, between Camp 
Yuma and Vallecito in the 1850s. Through the mid-1900s, most locality 
information came from California, where it became apparent that the 
flat-tailed horned lizard occupied the lower elevations of the Salton 
Trough in Riverside, Imperial, and San Diego Counties. Because of 
distinctive morphological characteristics, Hallowell (1852) first 
described the species as Anota M'callii, placing the flat-tailed horned 
lizard in a monotypic genus. The flat-tailed horned lizard remained a 
subject of taxonomic controversy for many years, occupying subsequently 
the genus Doliosaurus (Girard 1858), Phrynosoma (Cope 1866), and Anota 
(Cope 1900). Taxonomic questions were finally resolved by Norris and 
Lowe (1951), who determined that the similarities of this species to 
other horned lizards were more significant than its differences and 
placed the

[[Page 37853]]

species again in Phrynosoma. No subsequent change in the taxonomic 
status has been proposed for P. mcallii, other than clarification by 
Funk (1981) of the spelling of the specific epithet. The flat-tailed 
horned lizard is one of the more distinctive of the 13 species 
currently recognized in the genus.
    The flat-tailed horned lizard is endemic to the Sonoran Desert in 
the Coachella Valley in Riverside County, California; the Imperial and 
Borrego valleys in and near Anza Borrego and Ocotillo Wells in Imperial 
and eastern San Diego counties, California; south of the Gila River and 
west of the Gila and Tinajas Altas mountains in Yuma County, Arizona; 
east of the Sierra de Juarez in the Laguna Salada and Yreka Basins in 
northeastern Baja California Norte, Mexico; and north and west of Bahia 
de San Jorge to the delta of the Rio Colorado in northwestern Sonora, 
Mexico (Turner and Medica, 1982). The species occurs at elevations up 
to 800 meters (2600 feet) above sea level, but most populations are 
below 300 meters (980 feet) elevation. Within this range, the flat-
tailed horned lizard typically occupies sparsely vegetated, sandy 
desert flatlands with low species diversity, but it is also found in 
areas covered with small pebbles or desert pavement, mud hills, dunes, 
alkali flats, and low, rocky mountains. According to Hodges (1997), 
approximately 51.2 percent of the historic range of the flat-tailed 
horned lizard habitat within the United States is extant. An estimated 
maximum of 503,500 hectares (ha) (1,244,000 acres (ac)) of habitat 
remains in the United States, with approximately 56,800 ha (140,300 ac) 
found in Arizona and 446,670 ha (1,103,800 ac) found in California.
    Johnson and Spicer (1985) estimated that approximately 29 percent 
of the species' range occurs in Mexico; however, the distribution of 
the species in Mexico is poorly understood because of the lack of 
distribution inventories for the species. The acreage of suitable 
habitat found within the estimated range in Mexico is unknown. The 
species' distribution in Baja California Norte is limited by extensive 
agriculture that extends from Mexicali to the Colorado River and by the 
wetland and riparian communities of the Colorado River Delta, the Rio 
Hardy, and Laguna Salada. In Sonora, records indicate flat-tailed 
horned lizards exist primarily from an extensive sandy plain east of 
the Colorado River to the dunes of the Gran Desierto and also near 
Puerto Penasco. Between these areas is a relatively undisturbed region 
dominated by the large dune system of the Gran Desierto and volcanic or 
montane terrain in the Sierra Pinacate region, an area where few 
locality records exist and potential flat-tailed horned lizard habitat 
appears scattered (Gonzales-Romero and Alvarez-Cardenas 1989).
    Vegetation throughout the range of the flat-tailed horned lizard is 
predominantly Sonoran Desertscrub (Turner and Brown 1982). Flat-tailed 
horned lizards are found in habitat types including desert pavement, 
pebbled areas, mudhills, and dune edges. Characteristics of ``high 
quality'' flat-tailed horned lizard habitat include sparse vegetation, 
little slope, and surface soils of fine, packed sand or desert pavement 
overlaid intermittently with loose, fine sand (Turner et al. 1980). In 
Ocotillo Wells, however, recent work has found higher abundances of 
lizards in mudhills than in sandy areas (Wone 1997). The relationship 
between vegetation density and lizard abundance is unclear because of 
differences between study results. Wone (1996) found a negative 
correlation between lizard abundance and vegetation density, while 
Turner and Medica (1982) found a positive correlation between lizard 
abundance and perennial density. Altman et al. (1980) stated that when 
aggregate perennial densities are less than 250 per ha, ``the habitat 
is not likely to be favorable for P. mcallii. Almost all areas examined 
with high abundance of mcallii had aggregate perennial densities of 
greater than 1000/ha.''
    Because of difficulties in locating flat-tailed horned lizards, 
Turner et al. (1980) used scat counts to estimate the relative 
abundance of the species throughout its range. Broadly defined areas 
with high relative abundance of flat-tailed horned lizards have been 
found in California and Arizona using these methods and historical 
locality records. Turner and Medica (1982) identified four such areas 
in California, including southern East Mesa, southeastern Yuha Desert, 
the Superstition Mountain area in Imperial County, and the Benson Dry 
Lake area near Ocotillo Wells in San Diego County. Rorabaugh et al. 
(1987) identified one area of high relative abundance southeast of Yuma 
in Yuma County, Arizona. Although Muth and Fisher (1992) caution 
``habitat quality should not be inferred from scat counts,'' historical 
locality records support the assessment of habitat quality in the 
aforementioned areas.
    Rough estimates of flat-tailed horned lizard density have been made 
in different parts of the species' range. Estimated densities include 
0.3-1.5 lizards/ha (Rorabaugh 1994), 0.6 lizards/ha (Hodges 1995), 4.8-
8.4 lizards/ha (Turner and Medica 1982), and 1.3-1.39 lizard/ha (Muth 
and Fisher 1992). Rorabaugh (1994) recalculated the data presented by 
Turner and Medica (1982) using different analytical techniques, and 
arrived at a maximum density of 3.8/ha. Differences between studies in 
estimated density may represent differences in the lizard abundance in 
areas studied, differences in lizard abundance attributable to general 
declines in the species' abundance over the years between studies, or 
differences due to different methods of data collection and analysis. 
Approximately 503,500 ha (1,244,000 ac) of flat-tailed horned lizard 
habitat remain in the United States (derived from Hodges 1997), with 
approximately 176,800 ha (437,000 ac) of that habitat located within 
areas designated by Federal agencies as Flat-tailed Horned Lizard 
Management Areas (MAs) (Foreman 1997). Based on the density range (0.3-
3.8 lizards/ha) and habitat acreage estimates presented above, the 
population of lizards protected within MAs could range from 53,056 to 
672,045. These are rough estimates because habitat quality varies 
throughout MAs, some surface disturbance currently exists within the 
management areas, flat-tailed horned lizards are not evenly distributed 
across their range, and the large difference between the two density 
estimates is not accounted for in the literature. Even a population of 
a size at the low end of this range is large enough that it is not 
likely to be threatened by demographic and genetic factors.
    A Flat-tailed Horned Lizard Population Viability Analysis (PVA) was 
conducted by a Conservation Team convened to share research involving 
this species and to evaluate a proposed management strategy. The final 
PVA provided no estimate of the minimum viable population size and did 
not determine whether populations contained within the proposed 
management areas were viable. The Conservation Team concluded that 
further information was necessary to extrapolate from a PVA, but 
identified variables that apparently have a large effect on population 
viability. When introduced into modeled populations, variations in 
mortality, fecundity, number of egg clutches produced by a female in a 
year, and environmental conditions strongly affect population 
viability.
    In June, 1997, Federal and State agencies signed a Flat-tailed 
Horned Lizard Conservation Agreement (CA) and agreed to implement a 
Flat-tailed Horned Lizard Rangewide Management Strategy (Management 
Strategy). The

[[Page 37854]]

Management Strategy was developed by an interagency working group over 
a two-year period. As part of the CA, agencies delineated specified 
acreages under their jurisdiction as MAs. Approximately 176,800 ha 
(437,000 ac) of the remaining flat-tailed horned lizard habitat is 
found within MAs. This acreage represents approximately 35 percent of 
habitat remaining in the United States. Signatories of the CA, which 
include the Service, Bureau of Land Management (BLM), Bureau of 
Reclamation (BoR), U.S. Marine Corps, U.S. Navy, Arizona Game and Fish 
Department, and California Department of Parks and Recreation, 
committed to implementation of conservation measures for the species. 
These measures include: continuation of monitoring of lizard 
populations and new surface disturbance within MAs; limitation of 
surface-disturbing projects within MAs to one percent of the area of 
MAs over the course of the next five years; collection of compensation 
fees from project proponents conducting activities within MAs; 
reduction in off-highway vehicle (OHV) routes within MAs; prohibition 
of off-highway competitive events within MAs; support of continued 
flat-tailed horned lizard monitoring and research; mitigation for 
surface disturbing activities in lizard habitat; and attempting to 
acquire all private inholdings within MAs. Participation in the CA/
Management Strategy is voluntary, and agencies may withdraw from 
participation with 60 days notice.
    Prior to signing the agreement, agencies had already begun to 
implement planning actions identified as part of this agreement, 
including designation of MAs on BLM lands in California, application of 
mitigation measures on surface-disturbing projects on BLM lands in 
California, requiring compensation from project proponents conducting 
surface-disturbing activities in flat-tailed horned lizard habitat, 
designation of OHV routes on BLM lands in California (Foreman 1997), 
and acquisition of inholdings within the Yuma MA. Many of the measures 
identified in the CA are part of the agencies' ongoing management 
strategies and have been in place for years. Furthermore, the U.S. 
Marine Corps, at the Barry Goldwater Range in Arizona, has agreed to 
implement the terms and conditions of a conference opinion on ongoing 
activities, regardless of the species' status under the Act. Terms and 
conditions of the conference opinion include: limiting surface 
disturbance, enforcement of ``no trespass'' rules on the range, and 
initiation of a speed limit of 25 miles per hour on roads found within 
the range (U.S. Fish and Wildlife Service 1996). A Management Oversight 
Group, composed of managers from CA signatory agencies, was established 
to oversee implementation of the Management Strategy. This group first 
met on June 26, 1997.

Previous Federal Action

    The Service included the flat-tailed horned lizard as a category 2 
candidate for listing in its original Review of Vertebrate Wildlife, 
published in the Federal Register on December 30, 1982 (47 FR 58454). 
Category 2 candidates were those species for which data in the 
Service's possession indicated listing may be appropriate, but for 
which additional biological information was needed to support a 
proposed rule. This species was again included as a category 2 
candidate in the Service's revised Vertebrate Notice of Review of 
September 18, 1985 (50 CFR 37958). Subsequently, the status of the 
flat-tailed horned lizard was elevated to category 1 on January 6, 1989 
(54 FR 554), as new data on this species became available (Carlson and 
Mayhew 1988; Olech, undated; Rorabaugh et al. 1987). Category 1 
candidates were those species for which the Service had on file 
sufficient information to support issuance of proposed listing rules. 
On November 29, 1993, the Service published a proposal (58 FR 62624) to 
list the flat-tailed horned lizard as a threatened species.
    The Service held a public hearing on March 22, 1994, in Imperial, 
California, in response to formal requests from the public (59 FR 
8450). The public comment period on the proposed rule was reopened from 
February 22, 1994, until April 22, 1994. At that time, the Service was 
unable to make a final listing determination on this species because of 
higher listing priorities.
    On April 10, 1995, Congress enacted a moratorium on listing actions 
(Public Law 104-6) and eliminated funding for the Service to conduct 
final listing actions. The moratorium was lifted on April 26, 1996, by 
means of a Presidential waiver, at which time limited funding for 
listing actions was made available through the Omnibus Budget 
Reconciliation Act of 1996 (Pub. L. No. 104-134, 100 Stat. 1321, 1996). 
The Service published listing priority guidance for restarting the 
listing program on May 16, 1996 (61 FR 24722). When funding was 
restored, the Service commenced work on final actions, including the 
flat-tailed horned lizard proposed listing, in accordance with the 
listing priority guidance. The Service also coordinated with involved 
agencies on additional alternatives for conservation of the species.
    The BLM opened a public comment period on the draft Management 
Strategy from January 21, 1997, to March 19, 1997 (62 FR 3052). The 
Management Strategy was the product of numerous meetings between 
agencies and individuals with an interest in the flat-tailed horned 
lizard. Public meetings regarding the draft Management Strategy were 
held in El Centro, California, on February 19, 1997, and in Yuma, 
Arizona, on February 20, 1997. Comments were addressed by the BLM, and, 
on June 9, 1997, Federal and State agencies signed a CA to implement 
the Management Strategy.
    On March 5, 1997, the proposed rule comment period was reopened due 
to the time that had elapsed since the close of the initial comment 
period, changing procedural and biological circumstances, and the need 
to review the best scientific information available (62 FR 10016). The 
comment period was again extended for 30 days on May 6, 1997 (62 FR 
24632).
    On May 8, 1997, in response to a lawsuit filed by the Defenders of 
Wildlife, a U.S. District Court for the District of Arizona ruled that 
the Service must make a final determination on whether to list the 
flat-tailed horned lizard within 60 days of the filing date of the 
court order (May 16, 1997).
    The processing of this proposed rule conforms with the Service's 
final listing priority guidance published in the Federal Register on 
December 5, 1996 (61 FR 64475). The guidance clarifies the order in 
which the Service will process rulemakings during fiscal year 1997. The 
guidance calls for giving highest priority (Tier 1) to handling 
emergency situations, second priority (Tier 2) to resolving the listing 
status of the outstanding proposed listings, and third priority (Tier 
3) to new proposals to add species to the lists of threatened and 
endangered plants and animals. Processing of this proposed rule 
constitutes a Tier 2 action.

Public Comments on the Proposed Rule

    In the November 29, 1993, proposed rule (58 FR 62624) and 
associated notifications, all interested parties were asked to submit 
factual reports or information that might contribute to development of 
a final rule. Appropriate State agencies and representatives, 
scientific organizations, and other interested parties were contacted 
and requested to comment. A public hearing was held on March 22, 1994, 
at Imperial Valley College at which 11 individuals

[[Page 37855]]

testified. To allow for adequate public comment, the Service had four 
comment periods: November 29, 1993, to January 28, 1994 (58 FR 62624); 
February 22 to April 22, 1994 (59 FR 8450); March 5 to May 9, 1997 (62 
FR 10016); and May 9 to June 9, 1997 (62 FR 24632).
    During the comment periods, the Service received a total of 59 
comments (oral and written testimony) including 39 comments in support 
of Federal listing, 17 in opposition to Federal listing, and 2 neutral 
comments. Opposition to the listing proposal was expressed by two State 
agencies, two Federal agencies, five municipalities or municipal 
agencies, and eight other interested parties. Support for the listing 
was expressed by 1 Federal agency and 38 other interested parties.
    The proposed rule to list this species pre-dated the Service's 
policy to seek independent peer review (59 FR 34270). However, during 
the open comment periods, the Service solicited the expert opinions of 
appropriate independent specialists regarding pertinent scientific or 
commercial data and assumptions relating to the taxonomy and biological 
and ecological information for the flat-tailed horned lizard. The 
comments received were considered in making the Service's determination 
on the proposed rule.
    Written comments and oral statements obtained during the public 
hearing are incorporated into this withdrawal notice where appropriate. 
The Service carefully considered all comments submitted relevant to the 
decision to finalize or withdraw the proposed listing. Comments 
submitted are available for review at the Service's Carlsbad Ecological 
Services Office (see ADDRESSES section). Because it now withdraws the 
proposal to list the flat-tailed horned lizard, the Service will 
respond to issues raised in comments that supported listing. Seven 
relevant issues were raised in these comments, and the Service's 
response to each is as follows:
    Issue 1: Data on flat-tailed horned lizard population trends are 
unclear.
    Service Response: Quantification of flat-tailed horned lizard 
abundance is difficult due to the sedentary nature, cryptic coloration, 
and patchy distribution of this species. Turner et al. (1980) developed 
a survey technique to estimate the relative abundance of flat-tailed 
horned lizards based on counts of the number of scats observed per 
observer per hour. The technique, modified by Olech (undated), assumes 
the number of flat-tailed horned lizards is directly proportional to 
the number of scats and uses both the number of scats and number of 
lizards observed to estimate the relative lizard abundance. Surveys 
were conducted in 1979, 1981, 1984-1991, and 1993-1996 using this 
technique. The survey results have been used to estimate large-scale 
population trends (Wright 1993). Recently, the validity of this 
methodology has been reexamined (Wone 1997; Muth, in litt. 1997; Wright 
1993). The methodology does not account for variations in lizard 
activity, scat production due to fluctuating food resources, weather 
conditions that affect scat production or longevity in the field, 
observer capability, or small sample sizes (Rorabaugh 1994). Changes in 
scat abundance over time could be caused by changes in lizard activity 
or scat production rather than changes in population size. The 
Department of Defense (DoD) has recently funded work to assess the 
validity of using scat counts to determine relative abundance and to 
develop an improved survey technique. In the interim, a modified scat 
count method, still considered the best available technique, continues 
to be used to estimate population trends on BLM lands in California, 
and, in conjunction with habitat parameters and locality records, to 
determine presence or absence of the species.
    The relationship between scat counts and lizard abundance is 
unclear. Scat counts may provide a rough index for assessing relative 
abundance (Rorabaugh 1994), but Wone (1997) found that scat counts were 
not correlated to relative abundance at Ocotillo Wells in California. 
However, Wright (1993) found that scat counts were correlated with 
numbers of lizards encountered during scat surveys. Muth and Fisher 
(1992) concluded that scat counts should be used only to determine 
relative abundance, but not to estimate population size or habitat 
quality. Some researchers feel that scat counts consistently 
overestimate the number of flat-tailed horned lizards because other 
lizard species can produce scat similar in size (Muth, in litt. 1997).
    The information on population trends presented in the proposed rule 
was derived from scat count data collected between 1979 and 1991. 
Although the best information currently available on relative abundance 
and population trends of flat-tailed horned lizards is derived from 
scat counts, the confounding effects of scat persistence, heterogeneous 
scat distribution, variable rates of scat production, variations in 
survey methodology over time, and drought, including localized effects 
of low rainfall in different parts of the desert, make the population 
trend information derived from scat counts inconclusive. The population 
trends presented in the proposed rule showed that, between 1979 and 
1991, two areas, West Mesa and East Mesa, did not experience a 
significant downward population trend and one area, the Yuha Desert, 
experienced an overall downward population trend. However, later 
analyses performed subsequent to publication of the proposed rule show 
that the Yuha Desert experienced an upward trend between 1991 and 1993 
(Wright 1993) and no trend between 1993 and 1995 (Nicolai, unpublished 
data). The apparent downward population trend in the Yuha Desert noted 
in the proposed rule occurred in, and subsequent to, years 
characterized by drought. The observed downward trend may have been due 
to a temporary population decline or reduced scat production due to 
drought and reduction of food resources, rather than long-term habitat 
deterioration. In the short term, if flat-tailed horned lizards have 
less food resources available during drought years, a stable population 
may produce less scat as lizards become less active; this could cause 
erroneous population trend results (Rorabaugh 1994). Longer term 
declines in scat production during drought periods may be indicative of 
population reductions due to decreased reproduction or increased 
mortality.
    Other information on population trends is largely anecdotal. Turner 
et al. (1980) reported few flat-tailed horned lizards and low scat 
counts on and near Highway 78 in East Mesa, California, an area where 
the species was one of the most abundant lizard species in the 1960s 
(Carlson and Mayhew 1988). Norris (1949) believed the species was 
fairly common in the Coachella Valley where flat-tailed horned lizards 
are now difficult to find (Turner et al. 1980). Neither these 
observations nor trend data derived from scat counts are sufficient to 
conclude that the species' population is significantly declining in 
areas of extant habitat.
    Issue 2: Numerous comments supporting the proposal to list the 
flat-tailed horned lizard reiterate threats identified in the proposed 
rule, or identify new threats facing this species in portions of its 
range. Threats identified in comments include: current and projected 
habitat loss due to authorized and unauthorized off-highway vehicle 
activity; geothermal development; sand and gravel extraction; road 
construction; oil and gas leasing; powerline construction; canal or 
pipeline construction; Border Patrol off-road activity; lack of 
regulatory mechanisms (including unsuccessful BLM efforts to protect

[[Page 37856]]

species); residential, recreational, and industrial development; 
agriculture and resulting chemical pollution; land conversion on BLM 
inholdings authorized through the Imperial County General Plan; 
activities on lands adjacent to habitat; expansion of exotic plants 
into lizard habitat; increased fire frequency due to exotic plant 
expansion; and predation.
    Service Response: The threats to the flat-tailed horned lizard are 
addressed in detail in the ``Summary of Factors Affecting the Species'' 
section of this notice. Based on analyses conducted prior to the 
proposal to list the flat-tailed horned lizard, as well as from more 
recent analyses, an estimated 30-51 percent of historical flat-tailed 
horned lizard habitat in the United States was modified or destroyed in 
the past century. However, the extent of current rangewide threats 
facing remaining flat-tailed horned lizard populations is less clear. 
Although individual populations are threatened by residential, 
recreational, industrial, and agricultural development, large tracts of 
suitable habitat remain relatively undisturbed in Mexico and on public 
lands in the United States. Habitat found on public lands is protected 
to varying degrees by existing land-use designation. Significant 
potential threats to this species on public lands have been reduced or 
eliminated since publication of the proposed rule to list the species 
as threatened.
    Issue 3: Several commenters stated that the BLM in California has 
failed to implement planned actions in previous conservation plans and 
questioned the ability of the BLM in California to manage habitat for 
this species or to accomplish the goals established in the CA and 
Management Strategy.
    Service Response: The BLM has renewed and strengthened its 
commitment to the conservation of the flat-tailed horned lizard through 
participation in the development of the Management Strategy and 
subsequent signing of the CA. The Service anticipates that the BLM will 
implement the Management Strategy; however, the decision to withdraw 
the proposal to list the flat-tailed horned lizard is not based solely 
on BLM participation in the CA and Management Strategy. The flat-tailed 
horned lizard occurs not only on the BLM lands in California, but also 
on lands owned by the DoD, BoR, U.S. Marine Corps, U.S. Navy, BLM in 
Arizona, and California Department of Parks and Recreation. All of 
these agencies are signatories to the CA. The Service will continue to 
monitor the implementation of proposed actions through participation in 
the Interagency Coordinating Committee (ICC), and the Management 
Oversight Group designated in the CA. The BLM has demonstrated its 
commitment to implementation of the CA by already taking actions 
identified in the Management Strategy. Planning actions that are being 
implemented by BLM in California include: designation of MAs; 
application of mitigation measures to surface disturbing activities; 
collection of compensation fees for unavoidable habitat alteration due 
to surface disturbing activities; seeking acquisition of private 
inholdings within MAs; limitation of habitat disturbance within MAs to 
one percent; coordinating with the Border Patrol; initiation of OHV 
route designation and signing; and prohibiting insecticide treatments 
within MAs as outlined in the BLM Record of Decision for the Curlytop 
Virus Control Program.
    Issue 4: Proposed and anticipated development on public and private 
lands facilitated by the North American Free Trade Agreement (NAFTA) 
threatens flat-tailed horned lizard populations and potential habitat 
in the United States and Mexico.
    Service Response: Development due to NAFTA is likely to impact some 
flat-tailed horned lizard populations and some habitat in the United 
States and Mexico. However, the area likely to experience such 
disturbance is not adequately documented and the significance of this 
threat to the species as a whole can not be determined based on the 
limited available information.
    Issue 5: Off-highway vehicle activities pose continued threats to 
habitat throughout much of flat-tailed horned lizard range.
    Service Response: While OHV activity poses a potential local threat 
to the flat-tailed horned lizard, there is no documentation that OHV 
use poses a significant threat throughout the range of the species. 
Off-highway vehicles are known to cause lizard mortality and habitat 
disturbance (Muth and Fisher 1992, Rado 1981). The level of OHV 
activity, however, varies from a high level within OHV open areas to a 
low level in areas where existing routes are located miles apart. The 
zone impacted by established routes and the resulting impact on local 
lizard populations have not been determined.
    Although some studies found reduced scat abundance where vehicular 
tracks were abundant (Olech undated), studies that have attempted to 
assess impacts of OHV activity on flat-tailed horned lizards have been 
inconclusive. For example, Klinger et al. (1990) were not able to 
assess the effects of varying levels of OHV activity because the 
different levels of OHV activity which they examined occurred in 
different habitat types. In a small number of study plots (n=6) at the 
Imperial Sand Dunes (ISD) in southeastern California, Bury and 
Luckenbach (1983) found that areas impacted by OHV activity exhibited 
lower abundances of rodents, lizards, and plants than areas where there 
was no OHV activity. However, in plots of different levels of OHV 
activity, Wone et al. (1990) and Wright (1993) found no difference in 
the abundance of flat-tailed horned lizard scat. Some OHV activity 
causing habitat disturbance is unauthorized, but information concerning 
the amount and impact of unauthorized OHV activity is unavailable.
    Although OHV activity results in lizard mortality and habitat 
disturbance, there is no evidence, based on current data, that this 
activity is a significant threat to the species or is resulting in 
rangewide declines of flat-tailed horned lizard populations.
    Issue 6: Several commenters noted that there are research gaps 
involving the flat-tailed horned lizard that need to be better 
understood to develop conservation measures. Needs include researching 
lizard movements, ecology, recolonization potential, and nesting sites 
and studying the effects of OHVs on the species.
    Service Response: The Service agrees that a better understanding of 
a variety of aspects of flat-tailed horned lizard ecology, such as 
movement, habitat use, recolonization potential, age-specific 
survivorship, reproductive ecology, demographics, population viability, 
and effects of OHVs on the species, is necessary to develop proper 
conservation measures, and to better assess the status of the species.
    Issue 7: Several commenters who support listing the flat-tailed 
horned lizard as threatened question the ability of the CA and 
Management Strategy to sufficiently protect the flat-tailed horned 
lizard. Issues raised surrounding the CA include: enforceability of the 
CA, funding of the CA, the ability of the CA to remove threats, 
unprotected status of private inholdings found within the MAs and the 
Management Strategy's allowance of continued fragmentation.
    Service Response: The Service anticipates that continued 
implementation of the CA and Management Strategy will provide continued 
protection for this species on substantial acreages contained within 
MAs. The signatory agencies have begun implementation of actions 
identified within the Management Strategy and

[[Page 37857]]

have agreed to monitor surface disturbance and population trends, given 
the best available methodology, and report each on an annual basis to 
the Management Oversight Group. Furthermore, agencies have agreed to 
seek acquisition of all private inholdings within the boundaries of 
MAs. To date, private inholdings within the boundaries of MAs total 
approximately 19,280 ha (48,200 ac) (Foreman 1996). The BLM has 
informed the Service that it has issued a Notice of Proposed Exchange 
and is developing a Draft Environmental Assessment for a land exchange 
process whereby BLM acreage located outside of priority areas will be 
exchanged for private inholdings within BLM MAs. Priorities for 
inholding acquisition via this exchange include private inholdings 
found within Wilderness Areas, critical habitat designated for 
federally listed species, and Areas of Critical Environmental Concern 
(ACECs). The Marine Corps is in the process of acquiring all state 
lands found within the boundaries of the MA which lie within the Barry 
M. Goldwater Range. Funding is currently being sought by the Management 
Oversight Group for further implementation of the strategy. The 
Management Strategy focuses on five MAs that are disjunct, and it is 
the objective of the Management Strategy to provide enough protected 
area within each MA to sustain a viable population within each MA.
    It should be noted that, while the CA and Management Strategy are 
important tools in the conservation of the flat-tailed horned lizard, 
withdrawal of the proposal to list this species as threatened is not 
based solely on the CA and Management Strategy. Threats identified in 
the proposed rule have been reduced or eliminated since the publication 
of the proposed rule, and the information regarding population trends 
is inconclusive. The Management Strategy will, however, provide for 
conservation of the flat-tailed horned lizard on the extensive public 
lands on which it occurs and facilitate continued evaluation of the 
status of this species. The Service believes that the Management 
Strategy has and will continue to benefit flat-tailed horned lizard 
populations by significantly reducing the threats on public lands.

Summary of Factors Affecting the Species

    The Service must consider five factors described in section 4(a)(1) 
of the Act when determining whether to list a species. These factors, 
and their application to the Service's decision to withdraw the 
proposal to list the flat-tailed horned lizard, are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment 
of Its Habitat or Range

    Habitat loss has occurred throughout the range of the flat-tailed 
horned lizard. The proposed rule stated that approximately 34 percent 
of the historical habitat had been lost (23-27 percent in Arizona, and 
40 percent in California). According to Hodges (1997), using different 
methodologies from those used in the proposed rule, approximately 48.6 
percent of the historical range in the United States (31.1 percent in 
Arizona, and 50.2 percent in California) has been lost due to four 
primary activities; agriculture, filling the Salton Sea, urbanization, 
and military activities. Hodges (1997) analyzed the boundaries for the 
historical range, as well as the approximate total acreage of habitat 
remaining for this species. She estimates a maximum of 56,800 ha 
(140,300 ac) of habitat remain in Arizona, and, based on estimates of 
historical habitat and habitat loss, approximately 446,900 ha 
(1,103,800 ac) of habitat remain in California.
    The proposal to list the flat-tailed horned lizard as threatened, 
and comments received during the public comment period, identified 
human activities that have modified or were anticipated to modify the 
habitat. Activities that have disturbed habitat within the range of the 
flat-tailed horned lizard include: geothermal development; residential, 
recreational, and industrial development; agricultural conversion and 
resulting chemical pollution; sand and gravel extraction, oil and gas 
leasing; canal, pipeline, and transmission line construction; and 
authorized and unauthorized OHV activity.
    Loss of flat-tailed horned lizard habitat due to geothermal 
development historically has occurred on both private lands and BLM 
lands east of El Centro, California. Geothermal resources are known to 
occur in this area as part of the Known Geothermal Resource Area 
(KGRA). Historically, approximately 28,240 ha (69,760 ac) of potential 
flat-tailed horned lizard habitat were subject to geothermal 
development due to construction, maintenance and operation of 
geothermal powerplants within the KGRA. Because energy extraction 
technology within East Mesa has proven technologically unfeasible, and 
government subsidies have begun to expire, no new geothermal 
powerplants are proposed at this time (Larry Caffee, pers. comm. 1997). 
Consequently, future geothermal power plant construction and resulting 
habitat loss are not anticipated at this time.
    In the early 1980s, acreage throughout California was leased to oil 
and gas companies. Approximately 7,800 ha (19,200 ac) were estimated to 
be subject to oil and gas exploration and development based on pending 
oil and gas leases in 1980 (Rado 1981). This information was utilized 
in the proposed rule to list the flat-tailed horned lizard. Since the 
publication of the proposed rule, all oil and gas leases within the 
range of the flat-tailed horned lizard have expired (BLM 1996), and are 
not anticipated for renewal because of low likelihood of resource 
abundance (Foreman, pers. comm. 1996). Thus, habitat loss due to oil 
and gas exploration and development no longer threatens the species.
    Off-highway vehicle activities, including Border Patrol OHV 
activities and authorized and unauthorized recreational OHV activities, 
occur in many portions of the range of the flat-tailed horned lizard. 
The level of OHV activity, however, ranges from a high level in areas 
within OHV open areas to a low level in areas where existing routes are 
located miles apart. The zone impacted by established routes, and the 
resulting impact on local lizard populations is not known. The habitat 
disturbance caused by route proliferation in the desert is visually 
evident, but has not been adequately quantified at this time.
    Off-highway vehicle activity can crush burrows necessary to flat-
tailed horned lizards for temperature regulation (Wone 1997), can cause 
direct mortality (Muth and Fisher 1992), and modifies habitat through 
shrub loss, exotic plant introduction, and soil movement (Rado 1981). 
The overall impact of OHV activity on habitat and individual lizards 
likely depends on the frequency and intensity of use. In OHV Open Areas 
and the Ocotillo Wells State Vehicular Recreation Area (SVRA), which 
include an estimated 65,200 ha (161,000 ac) of potential flat-tailed 
horned lizard habitat, intensity of use is often high, and vehicular 
activity is not restricted to routes. However, the population trend 
data are inadequate to conclude that the flat-tailed horned lizard 
population in the Ocotillo Wells SVRA is declining. Flat-tailed horned 
lizard mortality on established trails has not been quantified, but is 
likely to occur because of the adaptations of this species for prey 
avoidance. This species relies on cryptic coloration for defense, and 
rarely flees when approached. Animals that do move, usually move short 
distances.

[[Page 37858]]

    This behavior, combined with shallow depths of hibernation during 
the winter months make mortality due to vehicular activity likely. The 
BLM is conducting a route designation process that administratively 
closes some existing routes, and will be continuing to work with off-
highway vehicular recreationists and wildlife biologists to identify 
routes unnecessary to the recreation community.
    No studies to date have documented the distance from a road over 
which any population declines or impacts may occur. Although some 
studies have found reduced scat abundance in areas with vehicular 
tracks (Olech undated), overall, studies that have attempted to assess 
the impacts of OHV use on flat-tailed horned lizards have been 
inconclusive. In a small number of plots (n=6) at the Imperial Sand 
Dunes in southeastern California, Bury and Luckenbach (1983) found that 
areas impacted by OHV use appeared to have lower abundance of rodents, 
lizards, and plants than in an equal number of control plots where 
there was no OHV use. However, in plots of different OHV use 
classification, Wone et al. (1990) and Wright (1993) found no 
difference in the abundance of flat-tailed horned lizard scat. Klinger 
et al. (1990) were not able to assess the effects of varying levels of 
OHV activity because the different levels of OHV activity which they 
examined occurred in different habitat types. Some disturbance due to 
OHV use is unauthorized, but information concerning the amount and 
impact of unauthorized use is unavailable. While OHV activity poses a 
potential local threat to individual flat-tailed horned lizard 
populations, there is no documentation that OHV use poses a significant 
threat throughout the range of the species.
    Residential, recreational and industrial development on private 
lands threaten some populations of flat-tailed horned lizards within 
the range of the species. However, because at least 50 percent of the 
habitat available to the species is located on public lands, because 
conservation measures are in place on these lands, and because the 
likelihood of large scale recreational and industrial development on 
these lands is low, urban, recreational, and industrial development 
does not significantly threaten the species.
    Agricultural conversion is one of the primary causes of habitat 
loss for the flat-tailed horned lizard. Conversion continues on many 
private parcels throughout the range of the species, most notably in 
Coachella Valley in Riverside County, and near San Luis and Yuma, 
Arizona. Like urban and industrial development, this impact is 
anticipated to occur largely on private lands. Agricultural conversion 
on public lands managed by signatories of the CA is not anticipated, 
but if it occurred, it would be subject to mitigation and compensation 
measures outlined in the Management Strategy. In addition, the 
signatories have committed to not authorize agricultural development in 
MAs. Because of the large acreage of habitat that exists on public 
lands where agricultural conversion is less likely to occur, the 
mitigation and compensation measures associated with surface 
disturbance on public lands managed by CA signatories, and the acreage 
further protected by the surface disturbance cap placed on MAs, 
agricultural conversion threatens local populations of the flat-tailed 
horned lizard, but does not threaten the species as a whole at this 
time.
    Sand and gravel extraction, and canal, pipeline, and transmission 
line construction are impacts on flat-tailed horned lizard habitat that 
have occurred on private and public lands, and may continue to do so in 
the future. Canals, such as the All-American and Coachella Canals, 
likely constitute complete or near complete barriers to movement of 
flat-tailed horned lizards, resulting in habitat fragmentation. The 
current extent of sand and gravel extraction pits on public lands is 
not documented, but Rado (1981) estimated 2,070 ha (5,120 ac) of active 
and intermittent sand and gravel quarries. This acreage represents a 
small percentage of the habitat present on public lands. Signatories to 
the CA have committed to locating such projects to areas outside of MAs 
to the maximum extent possible, and will apply appropriate mitigation 
and compensation measures, as identified in the Management Strategy, to 
all such projects. The BLM has required appropriate mitigation and 
compensation measures on BLM land since 1990.
    The Area Service Highway, a proposed highway that would connect 
Interstate 8 at Araby Road to the United States-Mexico Border, would 
fragment an area of high quality habitat. According to Hodges (1997), 
it would also result in approximately 830-1,040 ha (2,040-2,560 ac) of 
lost habitat and mortality of lizards. The highway is proposed for 
alignment along a portion of the western boundary of the Yuma MA. The 
habitat loss and potential future mortality and indirect impacts 
associated with construction of this road represent a local threat to 
the lizard population. This impact will be mitigated by on-site 
minimization measures and compensation fees which will be used for 
habitat acquisition within MAs.
    Because of the large amount of flat-tailed horned lizard habitat 
located on public lands within the United States and the reduction of 
threats on these lands due to changing land-use patterns and 
conservation efforts of public agencies, threats due to habitat 
modification and loss do not warrant listing of the species at this 
time.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    Although horned lizards have been popular in the pet industry, 
flat-tailed horned lizards are difficult to locate due to their cryptic 
coloration. No threat from overutilization of this species is known at 
this time.

C. Disease or Predation

    The Service is aware of parasitism by nematodes and red mites in 
some flat-tailed horned lizards (Norris 1949), but this is not 
considered to be a threat to the species (Bolster and Nocol 1989). 
Flat-tailed horned lizards are preyed upon by loggerhead shrikes, 
round-tailed ground squirrels, snakes, and canids (Muth and Fisher 
1992) as well as American kestrels, common ravens, and burrowing owls 
(Duncan et al. 1994). Because lizards remain on the surface and sleep 
at night, they may also be subject to predation by scorpions 
(Rorabaugh, pers. comm. 1997). Recent studies on telemetered animals in 
Arizona have revealed a high level of predation, with 30 percent of the 
marked lizards suffering mortality due to predation. Round-tailed 
ground squirrels and loggerhead shrikes were the primary predators 
identified. Further research is necessary on the effects of predation, 
and abundance and distribution of predators before the importance of 
this factor can be fully understood. There is no evidence of population 
declines in extant habitat where these predator species occur. Thus, 
based on the available data, disease and predation do not significantly 
threaten the species.

D. The Inadequacy of Existing Regulatory Mechanisms

    The conservation of this species is linked to the protection of the 
desert habitat. As outlined in the proposed rule, numerous regulatory 
mechanisms are currently in place to protect the flat-tailed horned 
lizard. In addition to the regulatory mechanisms in existence at the 
time of publication of the proposed rule, the CA and Management 
Strategy outlined in the ``Background'' section of this notice have 
been signed by the

[[Page 37859]]

Service, the BLM in California, the BLM in Arizona, the California 
Department of Parks and Recreation, the Arizona Department of Game and 
Fish, the BoR, the Commanding Officer of the Barry M. Goldwater Range, 
and the Commanding Officer of Naval Air Field El Centro. This agreement 
and associated strategy provide a framework for continued management of 
the flat-tailed horned lizard within the MAs designated by each of the 
landholding signatories.
    The States of California and Arizona prohibit the collection of 
flat-tailed horned lizards except by permit. The Arizona Game and Fish 
Department has further included the species on the List of Wildlife of 
Special Concern in Arizona. This list includes species that may be 
imperilled in Arizona. No state regulations protect the habitat of this 
species. Both the Arizona Game and Fish Department and the California 
Department of Parks and Recreation, however, have signed the CA and 
Management Strategy, which will provide for their continued 
participation in conservation efforts for this species. The Arizona 
Game and Fish Department does not own or manage flat-tailed horned 
lizard habitat but will continue to provide input on management 
decisions, as well as input regarding status and biology of the flat-
tailed horned lizard. The state of California has designated part of 
the Anza Borrego Desert State Park as an MA, which will limit surface 
disturbance that could be experienced in the park. Management in Anza 
Borrego is compatible with lizard conservation, due to the emphasis 
placed on resource protection, regulations limiting vehicles to 
designated trails, and enforcement of these policies. These policies 
have been in effect for a number of years. The Ocotillo Wells State 
Vehicular Recreation Area (SVRA) has supported research on the flat-
tailed horned lizard for several years, and will continue to do so as a 
signatory to the CA. The SVRA has been designated a ``Research Area'' 
in acknowledgment of continued support of research planned.
    In 1990 the California Department of Fish and Game and the BLM 
developed a joint Flat-tailed Horned Lizard Management Plan to address 
the species' conservation on BLM lands in California. The overall 
management goal of this plan is to maintain stable populations in all 
crucial habitat areas and to promote species recovery on BLM lands in 
California. The BLM has been in the process of implementing this plan 
since 1990.
    Within California, the lizard occurs in special management areas 
including three BLM Areas of Critical Environmental Concern (ACECs). 
These include the East Mesa, West Mesa and Yuha Desert ACECs. The ACECs 
overlap, in part, with the East Mesa, West Mesa, and Yuha Desert MAs. 
The East Mesa and Yuha Desert ACECs also fall within the boundaries of 
wildlife habitat areas that require preparation of habitat management 
plans to address the protection of special status species such as the 
flat-tailed horned lizard. This species also occurs within the 
boundaries of the San Sebastian Marsh ACEC and one Wilderness Study 
Area, the North Algodones Dunes Wilderness.
    The ACEC and wildlife habitat area designations have had limited 
success in protecting flat-tailed horned lizard habitat. Management 
prescriptions within ACECs include measures such as restricting OHV 
activity, but ACEC management goals include a provision to ``provide 
for other uses in the designated areas compatible with the protection 
of significant natural and cultural resources'' (BLM 1980). 
Participation of the BLM in the development of the Management Strategy, 
and subsequent signing of the CA increase the protection of flat-tailed 
horned lizards that will occur within ACECs where they overlap with 
MAs. The increase in protection will occur as a result of the process 
identified to facilitate OHV route minimization within MAs, the 
prohibition of OHV competitive events within MAs, and the limitation of 
surface disturbance activities to one percent of the total area of MAs 
over the course of the next five years.
    The North Algodones Dunes Wilderness is managed by the BLM for 
wilderness values. Motorized vehicular use is prohibited and the area 
shows little evidence of human intrusion. Limited habitat for the flat-
tailed horned lizard exists in the wilderness area, but these 
populations are protected by this designation.
    The flat-tailed horned lizard occurs in the Coachella Valley 
Preserve in Riverside County. It is reportedly not abundant within the 
Preserve, but these populations are not threatened.
    In Arizona, the species occurs within the boundaries of the Gran 
Desierto Dunes ACEC and the extreme western portion of the Tinajas 
Altas Mountains ACEC. In addition, an MA on BLM, DoD, and BoR lands has 
been designated. This MA occurs in the area of high relative abundance 
identified by Rorabaugh et al. (1987). Protection on the MA will 
include a cap on future surface disturbance of no more than one percent 
over the course of the next five years, as well as other conservation 
measures identified as part of the Management Strategy. The U.S. Marine 
Corps has agreed to comply with the terms and conditions of a 
conference opinion issued by the Service whether or not the species is 
listed. Terms and conditions, which are currently being implemented, 
include among others, limitations on surface disturbance, establishment 
of a speed limit, and enforcement of ``no trespass'' requirements. In 
addition, the Marine Corps is acquiring State of Arizona inholdings 
within the MA on the Barry M. Goldwater Range.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    Natural and manmade factors identified in the proposed rule as 
threats to the species included insecticide spraying associated with 
the Curlytop Virus Control Program and drought. Since publication of 
the proposed rule, the BLM has issued a Record of Decision prohibiting 
insecticide spraying in MAs. This spraying program was thought to have 
contributed to population declines in East Mesa (Bolster and Nicol 
1989). Since impacts due to pesticide application have been reduced, 
this activity no longer threatens flat-tailed horned lizard populations 
within MAs.
    Precipitation has been correlated with insect abundance and lizard 
densities (Turner et al. 1982). Within the range of the flat-tailed 
horned lizard, rainfall is highly unpredictable, both temporally and 
spatially (Turner and Brown 1982). Localized areas may experience long-
term drought, which may result in local decreases in lizard 
populations. Because of the fragmented distribution of the flat-tailed 
horned lizard, this unpredictability in precipitation increases the 
chance of localized extirpations. Data are inadequate to properly 
assess the degree to which drought or other naturally occurring events 
may increase the probability of extirpation.

Finding and Withdrawal

    The Service has carefully assessed the best scientific and 
commercial information available regarding the past, present, and 
future threats to this species. Flat-tailed horned lizard population 
trend data are inadequate to conclude that significant population 
declines have occurred in extant flat-tailed horned lizard habitat 
since publication of the proposed rule. Population trend information 
remains ambiguous due to uncertainties raised since publication of the 
proposed rule regarding survey methodology and analysis. Past and 
projected flat-tailed

[[Page 37860]]

horned lizard habitat loss due to agricultural, urban, industrial, and 
recreational development has and continues to occur on private lands. 
Large blocks of habitat with few anticipated impacts exist on public 
lands throughout the range of this species in East Mesa, West Mesa, 
Yuha Desert, Yuma, and Anza Borrego Desert. Since the publication of 
the proposed rule to list the flat-tailed horned lizard as threatened, 
several of the threats identified on public lands have been reduced or 
eliminated. Threats that have been reduced include those due to 
geothermal development, oil and gas development, and pesticide 
spraying. In addition, the conservation commitment of the agencies has 
increased with the signing of a CA and Management Strategy designed to 
protect the flat-tailed horned lizard on public lands. MAs have been 
designated in the Yuha Desert, West Mesa, East Mesa, Yuma Desert, and 
Anza Borrego State Park. Development of the CA has further reduced 
threats, as agencies begin to implement actions identified in the 
Management Strategy.
    Because of re-evaluation of information presented in the proposed 
rule, significant reduction of threats on public land, and 
uncertainties regarding population trend data, the Service determines 
that the flat-tailed horned lizard does not meet the required criteria 
to afford this species threatened status under the Act.
    The Service will work actively to gather additional information on 
its status as part of the Flat-tailed Horned Lizard Interagency 
Coordinating Committee. Further, the Service will continue to 
participate with parties of the CA to conserve this species as part of 
the Flat-tailed Horned Lizard Management Oversight Group.

References Cited

    A complete list of all references cited is available at the 
Carlsbad Field Office (see ADDRESSES above).

Author

    The primary author of this document is Sandy Vissman, Carlsbad 
Ecological Services Field Office (see ADDRESSES section).

Authority

    The authority for this action is section 4(b)(6)(B)(ii) of the 
Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: July 10, 1997.
John G. Rogers,
Acting Director, Fish and Wildlife Service.
[FR Doc. 97-18688 Filed 7-14-97; 8:45 am]
BILLING CODE 4310-55-P