[Federal Register Volume 64, Number 245 (Wednesday, December 22, 1999)]
[Proposed Rules]
[Pages 71714-71722]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-33087]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
RIN 1018-AF83
Endangered and Threatened Wildlife and Plants: Proposed
Endangered Status for the Southern California Distinct Vertebrate
Population Segment of the Mountain Yellow-Legged Frog
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
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SUMMARY: We, the Fish and Wildlife Service (Service), propose to list
the southern California distinct vertebrate population segment (DPS) of
mountain yellow-legged frog (Rana muscosa) as endangered, pursuant to
the Endangered Species Act of 1973, as amended (Act). In southern
California, this DPS has been reduced to only a few isolated remnants
in the San Gabriel, San Jacinto, and San Bernardino Mountains.
Hypothesized causes of the decline include predation from introduced
trout or possibly some other widespread environmental effects such as
airborne contaminants. These effects have probably acted in combination
to produce the decline. The chronology of the decline is not well
documented, but it appears that a precipitous decline occurred over the
last three or four decades. The decline went largely unnoticed and was
not studied. In addition to predation from trout and other widespread
factors, the few remaining frogs are now threatened by recreational
suction dredging for gold and human activities at campgrounds and day
use areas. The remnant populations are so small that they are now at
risk from random genetic, demographic, and environmental effects as
well. This proposed rule constitutes the 12-month finding on a petition
to list the southern California population of mountain yellow-legged
frog as threatened or endangered. This proposed rule, if made final,
would implement the Federal protection and recovery provisions afforded
by the Act for this DPS. We welcome data and comment from the public on
this proposal.
DATES: You must submit any comments by February 22, 2000 and public
hearing requests by February 7, 2000.
ADDRESSES: You may send comments and materials concerning this proposal
to the Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish
and Wildlife Office, 2730 Loker Avenue West, Carlsbad, California
92008. You may inspect comments and materials received, by appointment,
during normal business hours at the above address.
FOR FURTHER INFORMATION CONTACT: Ken Berg at the above address
(telephone 760/431-9440).
SUPPLEMENTARY INFORMATION:
Background
The mountain yellow-legged frog is a true frog in the family
Ranidae. Mountain yellow-legged frogs were originally described by Camp
in 1917 (as cited by Zweifel 1955) as a subspecies of Rana boylii.
Zweifel (1955) demonstrated that frogs from the high Sierra and the
mountains of southern California were somewhat similar to each other
yet were distinct from the rest of the R. boylii (=boylei) group. Since
that time, most authors have followed Zweifel, treating the mountain
yellow-legged frog as a full species, Rana muscosa.
Mountain yellow-legged frogs are moderately sized, about 40 to 80
millimeters (mm) (1.5 to 3 inches (in)) from snout to urostyle (the
pointed bone at the base of the backbone) (Jennings and Hayes 1994;
Zweifel 1955). The pattern is variable, ranging from discrete dark
spots that can be few and large, to smaller and more numerous spots
with a mixture of sizes and shapes, to irregular lichen-like patches or
a poorly defined network (Zweifel 1955). The body color is also
variable, usually a mix of brown and yellow, but often with gray, red,
or green-brown. Some individuals may be dark brown with little pattern
(Jennings and Hayes 1994). The back half of the upper lip is pale.
Folds are present on each side of the back, but usually they are not
prominent (Stebbins 1985). The throat is white or yellow, sometimes
with mottling of dark pigment (Zweifel 1955). The belly and
undersurface of the high limbs are yellow, which ranges in hue from
pale lemon yellow to an intense sun yellow. The iris is gold with a
horizontal, black counter shading stripe (Jennings and Hayes 1994).
In the Sierra Nevada Mountains of California, the mountain yellow-
legged frog ranges from southern Plumas County to southern Tulare
County (Jennings and Hayes 1994), at elevations
[[Page 71715]]
mostly above 1,820 meters (m) (6,000 feet (ft)). The frogs of the
Sierra Nevada are isolated from the frogs of the mountains of southern
California by the Tehachapi Mountains and a distance of about 225
kilometers (km) (140 miles (mi)). The southern California frogs now
occupy portions of the San Gabriel, San Bernardino, and San Jacinto
Mountains. Zweifel (1955) noted the presence of an isolated southern
population on Mt. Palomar in northern San Diego County, but this
population appears to be extinct (Jennings and Hayes 1994). In southern
California, the elevation range reported by Stebbins (1985) is 182 m
(600 ft) to 2,273 m (7,500 ft). Representative localities, including
some that are no longer occupied, which demonstrate the wide elevation
range that mountain yellow-legged frogs inhabited in southern
California, include Eaton Canyon, Los Angeles County (370 m (1,220 ft))
and Bluff Lake, San Bernardino County (2,290 m (7,560 ft)). The
southern California locations now occupied by mountain yellow-legged
frogs range from City Creek, in the San Bernardino Mountains (760 m
(2,500 ft)), to Dark Canyon in the San Jacinto Mountains (1,820 m
(6,000 ft)).
Southern California mountain yellow-legged frogs are diurnal,
highly aquatic frogs, occupying rocky and shaded streams with cool
waters originating from springs and snowmelt. In these areas, juveniles
and adults feed on small, streamside arthropods (Jennings and Hayes
1994). They do not occur in the smallest creeks. The coldest winter
months are spent in hibernation, probably under water or in crevices in
the bank. Mountain yellow-legged frogs emerge from overwintering sites
in early spring, and breeding soon follows. Eggs are deposited in
shallow water where the egg mass is attached to vegetation or the
substrate. In the Sierra Nevada, larvae select warm microhabitats
(Bradford 1984 cited in Jennings and Hayes 1994), and the time to
develop from fertilization to metamorphosis reportedly varies from 1 to
2.5 years (Jennings and Hayes 1994).
Prior to the late 1960s, mountain yellow-legged frogs were abundant
in many southern California streams (G. Stewart, in litt. 1995), but
they now appear to be absent from most places in which they previously
occurred. Jennings and Hayes (1994) believe that mountain yellow-legged
frogs are now absent from more than 99 percent of their previous range
in southern California. This decline is part of a well-known larger
pattern of declines among native ranid frogs in the western United
States (Hayes and Jennings 1986; Drost and Fellers 1996). Some of the
western ranid frog species experiencing noticeable declines are the
California red-legged frog (Rana aurora draytonii) (61 FR 25813), the
spotted frog (R. pretiosa and R. luteventris), the Cascades frog (R.
cascadae), and the Chiricahua leopard frog (R. chiricauhensis) (62 FR
49398). Nowhere have the declines been any more pronounced than in
southern California, where, besides declines in mountain yellow-legged
frogs, the California red-legged frog has been reduced to a few small
remnants (61 FR 25813), and the foothill yellow-legged frog (R. boylii)
may be extinct (Jennings and Hayes 1994.)
The mechanisms causing the declines of western frogs are not well
understood and are certain to vary somewhat among species, but the two
most common and well-supported hypotheses for widespread declines of
western ranid frogs are: (1) Past habitat destruction related to
unregulated activities such as logging and mining and more recent
habitat conversions for water development, irrigated agriculture, and
commercial development (Hayes and Jennings 1986; 61 FR 25813); and (2)
alien predators and competitors (Bradford 1989; Knapp 1996; Kupferberg
1997). Natural populations may be killed off directly by these factors
operating alone or in combination, or these factors so severely disrupt
the normal population dynamics that when local extinctions occur,
regardless of the cause, natural recolonization is impossible. Other
environmental factors that could have adverse effects over a wide
geographic range include pesticides, certain pathogens, and
ultraviolet-B (beyond the visible spectrum) radiation, but their role,
if any, in amphibian declines is not well understood (Reaser 1996).
These factors, acting singly or in combination, may be contributing to
widespread, systematic declines of western ranid frogs. Determining
their effects, however, is not an easy task (Reaser 1996; Wake 1998),
and the Department of the Interior (USDOI) currently supports an
initiative to fund research on the causes of amphibian declines (see
examples in USDOI 1998).
Some of the same factors that are hypothesized to have caused
declines of other western ranid frogs are likely to be responsible for
the reduction of the mountain yellow-legged frog in southern
California. Because the declines have been so precipitous, and have
spared only a small number of frogs in a few localities, the factors,
and their interactions, that caused the decline may never be fully
understood. We believe that these factors are still operating, and
unless reversed, a high probability exists that this frog may be
extinct in southern California within a few decades. In the case of the
mountain yellow-legged frog, the only factor listed above that we
believe can be ruled out as a likely cause of decline is habitat
destruction related to activities such as logging, mining, irrigated
agriculture, and commercial development. The range of the mountain
yellow-legged frog in southern California is mainly on public land
administered by the U.S. Forest Service (FS). Most of the rugged
canyons and surrounding mountainous terrain have been altered little
and look much the same today as they did when earlier naturalists such
as Lawrence Klauber collected mountain yellow-legged frogs there in the
early decades of the 1900s.
Current Range and Status
In southern California, mountain yellow-legged frogs can still be
found in four small streams in the San Gabriel Mountains, the upper
reaches of the San Jacinto River system in the San Jacinto Mountains,
and at a single locality on City Creek, a tributary of the Santa Ana
River, in the San Bernardino Mountains (Jennings and Hayes 1994; M. D.
Wilcox in litt., 1998). These areas along with the numbers of frogs
most recently observed in each area are described below.
San Gabriel Mountains: Surveys conducted from 1993 to 1997 revealed
small isolated populations in the upper reaches of Prairie Creek/
Vincent Gulch, Devil's Canyon, and Alder Creek/East Fork, on the East
Fork of the San Gabriel River, and Little Rock Creek on the Mojave
River (Jennings and Hayes 1994 and references therein; Jennings 1995;
Jennings 1998). The surveys involved one to three field biologists and
were conducted over 1-5 days per site. Over the course of these field
studies, 15 adults or fewer were observed at any 1 site, and, after the
1995 season, Jennings (1995) concluded that the actual population at
each of the sites was only 10-20 adults.
San Jacinto Mountains: Small populations of mountain yellow-legged
frogs also occur in four tributaries in the upper reaches of the North
Fork, San Jacinto River on Mount San Jacinto: Dark Canyon, Hall Canyon,
Fuller Mill Creek, and the main North Fork, San Jacinto River (Jennings
and Hayes 1994; Jennings 1995; Jennings 1998). The number of frogs
occupying these sites is not known, but fewer than 10 adult frogs per
site per year have been observed in surveys from 1995 to the present.
San Bernardino Mountains: A few tadpoles and 26 recently
transformed
[[Page 71716]]
juveniles, but no adults, were rediscovered on a roughly 1-mile reach
of the East Fork, City Creek during the summer of 1998 (M. D. Wilcox in
litt., 1998). Previous to this finding, mountain yellow-legged frogs
had not been observed in the San Bernardino Mountains since the 1970s
(Jennings and Hayes 1994), even though surveys were conducted during
the summer and fall of 1997 and 1998 (Holland 1997; Tierra Madre 1999).
When frogs were encountered during field surveys accomplished
between 1988 and 1995, only a few individuals were observed. Jennings
and Hayes (1994) and Jennings (1995) suggested that the entire
population of mountain yellow-legged frogs in the San Gabriel and San
Jacinto Mountains (8 more or less isolated sites) was probably fewer
than 100 adult frogs. Their rough estimate is based on a compilation of
the results of visual surveys generally conducted on a single day, not
on formal population abundance estimation techniques. While the precise
number of adult frogs may be greater than 100, we concur with Jennings
and Hayes (1994) that, in the San Gabriel and San Jacinto Mountains,
the available data indicate that this once widespread species is now
found in only a small number of relatively isolated populations. We do
not know the population size of adult frogs at the recently
rediscovered site on the east fork of City Creek in the San Bernardino
Mountains, but because no adults and only a few juveniles and tadpoles
were encountered, the adult population is probably small. Thus, we
conclude that each of the three mountain ranges (San Gabriel, San
Jacinto, San Bernardino) contains a small number of small, relatively
isolated populations.
Distinct Vertebrate Population Segment
We analyzed the mountain yellow-legged frog according to the joint
Service and National Marine Fisheries Service Policy Regarding the
Recognition of Distinct Vertebrate Populations, published in the
Federal Register on February 7, 1996 (61 FR 4722). We consider three
elements in determining whether a vertebrate population segment could
be treated as threatened or endangered under the Act: discreteness,
significance, and conservation status in relation to the standards for
listing. Discreteness refers to the isolation of a population from
other members of the species and is based on two criteria: (1) Marked
separation from other populations of the same taxon resulting from
physical, physiological, ecological, or behavioral factors, including
genetic discontinuity, or (2) populations delimited by international
boundaries. We determine significance either by the importance or
contribution, or both, of a discrete population to the species
throughout its range. Our policy lists four examples of factors that
may be used to determine significance: (1) Persistence of the discrete
population segment in an ecological setting unusual or unique for the
taxon; (2) evidence that loss of the discrete population segment would
result in a significant gap in the range of the taxon; (3) evidence
that the discrete population segment represents the only surviving
natural occurrence of the taxon that may be more abundant elsewhere as
an introduced population outside its historic range; and (4) evidence
that the discrete population segment differs markedly from other
populations of the taxon in its genetic characteristics. If we
determine that a population segment is discrete and significant, we
evaluate it for endangered or threatened status based on the Act's
standards.
Discreteness: The range of the mountain yellow-legged frog is
divided by a natural geographic barrier, the Tehachapi Mountains, which
isolate Sierran frogs from those in the mountains of southern
California. The distance of the separation is about 225 km (140 mi),
but the separation may not have been this great in the recent past
because a frog collected in 1952 on Breckenridge Mountain in Kern
County was identified by Jennings and Hayes (1994) as a mountain
yellow-legged frog. The geographic separation of the Sierran and
southern California frogs was recognized in the earliest description of
the species by Camp (1917, cited in Zweifel 1955), who treated frogs
from the two localities as separate subspecies within the R. boylii
group. He designated the Sierran frogs R. b. sierrae and the southern
California frogs R. b. muscosa, based on geography and subtle
morphological differences. Zweifel (1955) reevaluated the morphological
evidence and found it insufficient to warrant Camp's recognition of two
subspecies, the chief difference between the two being hind-limb
length.
More recently, Ziesmer (1997) analyzed the calls of Sierran (Alpine
and Mariposa Counties) and southern California (San Jacinto Mountains
and Riverside County) mountain yellow-legged frogs. He found that the
calls of Sierran frogs differed from southern California frogs in pulse
rate, harmonic structure, and dominant frequency. Based on a limited
sample, Ziesmer concluded that the results supported the hypothesis
that mountain yellow-legged frogs from the Sierra Nevada and southern
California are separate species.
Allozyme (a form of an enzyme produced by a gene) variation
throughout the range of the mountain yellow-legged frog has been
examined, but the results are open to interpretation (Jennings and
Hayes 1994 and references therein). In the work most applicable to the
question of the distinctiveness of the Sierran and southern California
frogs, David Green (pers. comm., 1998) analyzed allozyme variation in
central Sierran mountain yellow-legged frogs (four individuals,
Tuolumne County) and southern California mountain yellow-legged frogs
(two individuals, Riverside County). He found fixed differences at 6 of
28 loci (sites on a chromosome occupied by specific genes). These
limited, unpublished data suggest that Sierran and southern California
mountain yellow-legged frogs are different at a level that could
support the recognition of full species. However, because of the small
number of individuals per sample and the limited number of samples, we
view these results cautiously. It is possible that existing variation
at those six loci may not have been detected with such a small number
of individuals sampled. To better understand whether a genetic
discontinuity significant enough to warrant full species rank exists
between Sierran frogs and those from the mountains of southern
California, samples of frogs from the southern Sierra Nevada,
especially the Greenhorn Mountains, would be of particular interest.
Although Green's limited allozyme analysis may not be sufficient to
support recognizing the Sierran and southern California populations as
separate species, it does support the conclusion of significant
geographic separation. This conclusion is also supported by earlier
observations of morphological differences (Zweifel 1955, and references
therein) and differences in vocalizations (Ziesmer 1997). Considered
together, the evidence supports an interpretation of isolation between
the two populations of frogs over a very long period. We find that the
southern California frogs meet the criterion of ``marked separation
from other populations of the same taxon'' and qualify as discrete
according to the Policy Regarding the Recognition of Distinct
Vertebrate Populations (61 FR 4722).
Significance: One of the most striking differences between Sierran
and southern California mountain yellow-legged frogs is the habitats
they occupy. Zweifel (1955) observed that the frogs in southern
California are typically found
[[Page 71717]]
in steep gradient streams in the chaparral belt, even though they may
range up into small meadow streams at higher elevations. In contrast,
Sierran frogs are most abundant in high elevation lakes and slow-moving
portions of streams. Bradford's (1989) southern Sierra Nevada study
site, for example, was in Sequoia and Kings Canyon National Parks at
high elevations (between 2,910-3,430 m (9,600-11,319 ft)). The rugged
canyons of the arid mountain ranges of southern California bear little
resemblance to the alpine lakes of the Sierra Nevada. On the basis of
habitat alone, one might easily conclude that these are two very
different frogs.
The mountain yellow-legged frogs of southern California comprise
the southern portion of the species' range. The extinction of this
southern group would be significant because it would substantially
reduce the overall range as it is currently understood, and what is now
a gap in the distribution, the Tehachapi Mountains, would become the
southern limit of the species' range.
In addition, evidence exists that the mountain yellow-legged frog
is not simply a single species with a disjunct distribution (cited in
Zweifel 1955; Stebbins 1985). As discussed above, vocal and genetic
differences exist between Sierran and southern California mountain
yellow-legged frogs. Although the data are limited and some important
variation may have been missed, they are consistent with the earlier
interpretation by Camp (1917 cited in Zweifel 1955) and numerous other
authors prior to Zweifel (e.g., Stebbins 1954) who treated the two
forms as taxonomically distinct. If the differences in vocalization
described by Ziesmer (1997) and the allozyme variation described by
Green (per. comm., 1998) accurately characterize differences between
the two forms, then the Sierran and southern California frogs are quite
different and have been isolated for a very long time.
Our conclusion that Sierran and southern California frogs are very
different from each other, and may even merit recognition as separate
subspecies or possibly even species, is based on the cumulative weight
of the available evidence. We find that the mountain yellow-legged
frogs inhabiting the mountains of southern California meet the
significance criteria under our Policy Regarding the Recognition of
Distinct Vertebrate Populations (61 FR 4722) on the basis of the
geographical, ecological, vocal, and genetic discontinuities described
above.
In the remainder of this proposed rule, we evaluate the southern
California mountain yellow-legged frog for endangered status based on
the Act's standards. For clarity, we refer to all mountain yellow-
legged frogs south of the Tehachapi Mountains as the southern
California DPS. We use the word ``population'' to describe all of the
frogs living in a particular place.
Previous Federal Action
On July 13, 1995, we received a petition dated July 10, 1995, from
D.C. ``Jasper'' Carlton (of the Biodiversity Legal Foundation), Bonnie
M. Dombrowski, and Michael C. Long to list as threatened or endangered
the southern California populations of the mountain yellow-legged frog
(Rana muscosa) pursuant to the Act. Accompanying the petition was
supporting information related to the taxonomy, ecology, and the past
and present distribution of the species. We reviewed the petition,
supporting documentation, and other information cited in this proposed
rule to determine if substantial information was available to indicate
that the requested action may be warranted. On July 8, 1997, we
published a 90-day finding for the petition to list the southern
California populations of the mountain yellow-legged frog (62 FR
36481). We found the southern California population to be a DPS and
furthermore found the petition presented substantial information
indicating the listing of the species (DPS) may be warranted. Once we
made the finding that the petition presented substantial information,
we commenced a status review pursuant to section 4(b)(3)(A) of the Act.
However, consistent with the applicable Listing Priority Guidances (62
FR 55268; 63 FR 25502), our Carlsbad Field Office completed work on
higher priority listing actions before completing this 12-month finding
and proposed rule to list this DPS of the mountain yellow-legged frog.
The processing of this proposed rule conforms with our Listing
Priority Guidance published in the Federal Register on October 22, 1999
(64 FR 57114). The guidance clarifies the order in which we will
process rulemakings. Highest priority is processing emergency listing
rules for any species determined to face a significant and imminent
risk to its well-being (Priority 1). Second priority (Priority 2) is
processing final determinations on proposed additions to the lists of
endangered and threatened wildlife and plants. Third priority is
processing new proposals to add species to the lists. The processing of
administrative petition findings (petitions filed under section 4 of
the Act) is the fourth priority. The processing of critical habitat
determinations (prudency and determinability decisions) and proposed or
final designations of critical habitat will be funded separately from
other section 4 listing actions and will no longer be subject to
prioritization under the Listing Priority Guidance. The processing of
this proposed rule is a Priority 3 action.
Summary of Factors Affecting the Species
Section 4 of the Endangered Species Act (16 U.S.C. 1531 et seq.)
and the regulations (50 CFR part 424) that implement the listing
provisions of the Act set forth the procedures for adding species to
the Federal lists. A species may be determined to be an endangered or
threatened species due to one or more of the five factors described in
section 4(a)(1). These factors and their application to the southern
California DPS of mountain yellow-legged frogs are as follows:
A. The Present or Threatened Destruction, Modification, or Curtailment
of its Habitat or Range.
All nine known populations of southern California Rana muscosa
occur on lands owned and managed by the FS and are clustered within
three drainages, one in the San Gabriel Mountains, one in the San
Bernardino Mountains, and another on Mount San Jacinto. As such, the
habitats in which they live are protected against wholesale conversions
to other uses. However, with so few populations remaining, and with
each of those numbering only a few individuals, localized habitat
alterations, which would not be appreciable if the DPS were more wide-
ranging and abundant, threaten the DPS. Local habitat changes caused by
recreational suction dredging for gold and human use around
campgrounds, picnic grounds, and heavily used trails may harm the
habitat and contribute to local extinctions wherever these activities
intersect with mountain yellow-legged frogs.
Jennings (1995) observed suction dredging within the Wilderness
Area where mountain yellow-legged frogs occur on the East Fork, San
Gabriel River. He reported observing large quantities of trash and
toxic materials being dumped into the stream bed. If this practice is
continued, it could have harmful effects on the population inhabiting
the East Fork, San Gabriel River. The consequences for populations on
other San Gabriel River tributaries is difficult to predict, but any
losses would further isolate the remaining populations and probably
[[Page 71718]]
reduce the time to extinction for the DPS. Other than the East Fork,
San Gabriel River site, we do not know if recreational gold mining
occurs or at what level on or near sites occupied by frogs. Extensive
suction dredging activity at or near a breeding site could have the
harmful effect of killing eggs or larvae or changing the hydrology,
rendering it unsuitable for breeding. Some of the habitat effects of
suction dredging on streams are described by Harvey (1986), who found
dredging altered substrates and changed the habitat for fish and
invertebrates.
Fairly heavy camping and day use coincides with frog habitat along
the East Fork, San Gabriel River (dispersed camping), Prairie Fork
Creek (campground, recently burned and presently closed by the FS),
Little Rock Creek (trail, rock climbing), Dark Canyon (campground), and
Fuller Mill Creek (picnic ground). In areas occupied by frogs, human
presence in and along streams can disrupt the lives of eggs, larvae,
and adult frogs and change the entire character of the stream and its
bank and associated vegetation in ways that make whole sections of
stream less suitable for frogs. Only nine very small populations
remain, and at least four of these are in areas that receive reasonably
heavy human camping or day use. The loss of even small numbers of frogs
from any of these populations due to human camping or day use, either
alone or in combination with other factors, will increase the
probability of local extinction. Any local extinctions will further
isolate the remaining populations and probably reduce the time to
extinction for the DPS.
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Numerous museum specimens from many localities (Jennings and Hayes
1994) attest to the fact that, for decades, mountain yellow-legged
frogs from the southern DPS have been collected for scientific
purposes. These collections probably did not have an appreciable
effect. Now that the DPS has declined precipitously, populations are so
few in number, and the size of each population is so small, very little
or no scientific collecting of the southern DPS occurs. Collecting,
scientific or amateur, if it did occur, could seriously increase the
probability of extinction of any of the remaining populations. Any
local extinctions will further isolate the remaining populations and
probably reduce the time to extinction for the DPS.
C. Disease or Predation
Predation by introduced trout, including rainbow trout
(Oncorhynchus mykiss), is one of the best documented causes of the
decline of Sierran mountain yellow-legged frogs. Careful study of the
distributions of introduced trout and mountain yellow-legged frogs for
several years has shown conclusively that introduced trout have had
negative impacts on mountain yellow-legged frogs over much of the
Sierra Nevada (Bradford 1989; Knapp 1996). Bradford (1989) and Bradford
et al. (1993) concluded that introduced trout eliminate many
populations of mountain yellow-legged frogs and the presence of trout
in intervening streams sufficiently isolates other frog populations so
that recolonization after stochastic (random, naturally occurring)
local extinctions is essentially impossible. This mechanism is
sufficient to explain the elimination of Sierran mountain yellow-legged
frogs from the majority of sites they once inhabited, and, alone or in
combination with other factors, introduced trout have almost certainly
contributed to the widespread and systematic decline of the southern
DPS as well.
Virtually all streams in the mountains of southern California
contain populations of introduced rainbow trout, and trout are
routinely planted in Dark Canyon, Fuller Mill Creek in the San Jacinto
Mountains, and City Creek in the San Bernardino Mountains. Most of the
other streams still occupied by mountain yellow-legged frogs have
histories of trout introductions and probably contain naturally
reproducing, sustainable populations at, or very near, the sites
occupied by the frogs. Wherever the two species co-occur, trout are
likely to eliminate mountain yellow-legged frogs or keep populations
low and limit dispersal. The widespread occurrence of introduced trout
in the mountains of southern California may make it very difficult to
reverse the decline to extinction of the DPS.
Another introduced predator that could have effects on the DPS
similar to those of the trout, yet on a more limited scale, is the
bullfrog, Rana catesbeiana. Bullfrogs have been listed among the
threats to other western frogs (61 FR 25813; Kiesecker and Blaustein
1998) and toads (59 FR 64859). Bullfrogs are now widespread in southern
California and occur in many drainages formerly and currently occupied
by mountain yellow-legged frogs. The negative effects of bullfrogs on
mountain yellow-legged frogs in the mountains of southern California
are probably less widespread than those of introduced trout because
there is less overlap in their occurrence. Any habitat alterations that
are favorable to bullfrogs, however, will cause them to become abundant
locally. In areas where mountain yellow-legged frogs occur, this
increase could lead to local extinctions and increased isolation of the
remaining populations, which would probably reduce the time to
extinction for the entire DPS.
Bradford (1991) documented the loss of a Sierran population of Rana
muscosa due to the combined effect of ``red-leg'' disease (caused by
the bacterium Aeromonas hydrophila) and predation by Brewer's
blackbirds, Euphagus cyanocephalus. Another pathogen that is generating
concern among those who study amphibian declines is the chytrid fungus.
Chytrids may be seriously affecting amphibians in many places around
the world, and they have recently been discovered on larval mountain
yellow-legged frogs in the Sierra Nevada (Gary Fellers, pers. comm.
1999). Because of the small and isolated nature of the remaining
populations, disease could be serious. Any local extinctions caused by
disease would further isolate the remaining populations and probably
reduce the time to extinction for the entire DPS.
D. The Inadequacy of Existing Regulatory Mechanisms
Existing regulatory mechanisms have not stopped the decline of
mountain yellow-legged frogs in southern California. Existing
regulatory mechanisms that could provide some protection for the
mountain yellow-legged frog include: (1) Consideration under the
California Environmental Quality Act (CEQA); (2) consideration under
section 404 of the Clean Water Act (CWA); and (3) co-occurrence with
other species protected by the Endangered Species Act of 1973.
The State of California considers mountain yellow-legged frogs a
species of special concern, but it is not a threatened or endangered
species and receives no protection under the California Endangered
Species Act. California Sport Fishing Regulations include the mountain
yellow-legged frog as a protected species that may not be taken or
possessed at any time except under special permit from the California
Department of Fish and Game. This prohibition may help prevent threats
from collecting, but this threat is not a significant cause of the
decline, and the DPS is expected to continue declining toward
extinction even in the absence of collecting.
The CEQA requires a full public disclosure of the potential
environmental impact of proposed
[[Page 71719]]
projects. The public agency with primary authority or jurisdiction over
the project is designated as the lead agency and is responsible for
conducting a review of the project and consulting with other agencies
concerned with resources affected by the project. Section 15065 of the
CEQA guidelines require a finding of significance if a project has the
potential to ``reduce the number or restrict the range of a rare or
endangered plant or animal.'' Species that are eligible for listing as
rare, threatened, or endangered but are not so listed are given the
same protection as those species that are officially listed with the
State. Once significant impacts are identified, the lead agency has the
option to require mitigation for effects through changes in the project
or to decide that overriding considerations make mitigation infeasible.
In the latter case, projects may be approved that cause significant
environmental damage, such as destruction of endangered species.
Protection of listed species through CEQA is, therefore, at the
discretion of the lead agency involved. The CEQA provides that, when
overriding social and economic considerations can be demonstrated,
project proposals may go forward, even in cases where the continued
existence of the species may be threatened, or where adverse impacts
are not mitigated to the point of insignificance.
Besides the Act, the primary Federal law that potentially affords
some protection for the mountain yellow-legged frog is section 404 of
the CWA. The CWA may provide some general protections for species,
however, this DPS has declined precipitously under this Federal law.
The arroyo toad (Bufo microscaphus californicus), a federally
listed endangered species, is present in the San Gabriel Mountains, but
there is no benefit to the mountain yellow-legged frog because the two
species occupy different areas in the San Gabriel Mountains and the
arroyo toads are not known to occur elsewhere in the limited range of
the mountain yellow-legged frog.
The Angeles and San Bernardino National Forests manage all known
locations of mountain yellow-legged frogs in southern California.
However, the FS does not include Rana muscosa on its list of sensitive
species, although the Angeles and San Bernardino National Forests
manage the frog as if it were sensitive (M. Rogers, in litt., 1997).
Nevertheless, the FS does not have a management plan for the mountain
yellow-legged frog or an adaptive management strategy that addresses
the specific conservation and recovery needs of the species. As noted
in the discussion of factors A through C above, the presence of
introduced trout on FS lands is a serious threat, and, now that the DPS
has been reduced to small isolated remnants, some other legal
recreational activities occurring on FS lands may threaten the
remaining frogs. The perilous status of the mountain yellow-legged frog
reflects the overall failure or inability of existing CEQA, National
Environmental Policy Act, and other Federal, State, and local
ordinances and statutes to protect and provide for the conservation of
this DPS.
E. Other Natural or Manmade Factors Affecting its Continued Existence
Because the remaining populations of the DPS are small, isolated
remnants, they are vulnerable to random natural events that could
quickly eliminate them. It is a widely recognized principle that, in
general, small populations are more vulnerable to extinction than large
ones (Pimm 1991; Noss and Cooperrider 1994). Noss and Cooperrider
(1994) identified four major factors that predispose small populations
to extinction: (1) Environmental variation and natural catastrophes
like unusually harsh weather, fires, or other unpredictable
environmental phenomena; (2) chance variation in age and sex ratios or
other population parameters (demographic stochastisity); (3) genetic
deterioration resulting in inbreeding depression and genetic drift
(random changes in gene frequencies); and (4) disruption of
metapopulation dynamics (i.e., some species are distributed as systems
of local populations linked by occasional dispersal, which wards off
demographic or genetic deterioration).
It is likely that some or a combination of these factors contribute
to an increased probability of extinction of the remaining populations
and the entire DPS. For example, Stewart (in litt., 1995) and Jennings
(in litt., 1995) believe that flooding and fires could easily eliminate
entire populations of mountain yellow-legged frogs, and Stewart (in
litt., 1995) believes flooding during the winter of 1969 was the major
factor in the loss of mountain yellow-legged frogs from Evey Canyon in
the San Gabriel Mountains. An illustration of possible demographic
effects is seen in the results of a limited survey by Jennings (1995),
who found skewed sex ratios in the San Gabriel Mountains populations.
If the results accurately reflect the real sex ratios in these
populations, the effective population sizes are much lower than the
census populations. When effective population size is small, the
negative consequences can be demographic (e.g., not enough individuals
of a given sex) or genetic (e.g., inbreeding depression), and can
predispose these populations to a higher risk of extinction. The
population genetics and metapopulation dynamics of the southern
mountain yellow-legged frog have not been investigated, but we believe
that the connectivity of populations within the DPS is substantially
reduced compared to the recent past.
Because the southern DPS consists of small, isolated populations,
it is particularly vulnerable to some or all of the effects of chance
listed above. Given the low probability of improving the status of the
DPS under the status quo, the probability of small population size
playing a role in the extinction of one or more local populations
within the next few years is high. Any local extinctions will further
isolate the remaining populations and probably reduce the time to
extinction for the entire DPS.
In summary, in southern California the mountain yellow-legged frog
DPS is threatened by predation from introduced trout and possibly by
other factors (e.g., airborne contaminants, pathogens) that are
difficult to pinpoint and are currently the subject of national and
worldwide investigations. Other local factors (recreational dredging,
camping, day use), that would not cause appreciable harm if the DPS had
not been reduced to small remnants, now represent serious actual or
potential local threats. Compounding the effects of the large-scale
(trout) and local (recreation) threats, the DPS has been reduced to
very small isolated or semi-isolated populations that random events are
now likely to contribute to local extinctions, which will reduce the
time to extinction of the entire DPS. Even though we may never fully
understand all the causes of decline, the available information
suggests a high probability that this frog may be extinct in southern
California within a few decades. We have carefully assessed the best
scientific and commercial information available regarding the past,
present, and future threats facing the DPS in determining to propose
listing. Based on this evaluation, we propose to list the southern
California DPS of mountain yellow-legged frog as endangered. We
considered but did not select other alternatives to this action because
not listing this DPS as endangered, or listing it as threatened, would
not provide adequate protection and would not be in keeping with the
purpose of the Act or the definitions therein. This DPS consists of 9
small, relatively isolated
[[Page 71720]]
populations from which a combined total of fewer than 100 adults have
been observed in recent surveys. Although all of the factors that have
caused it to decline to this low level may never be known, the DPS is
in immediate danger of extinction.
Critical Habitat
Critical habitat is defined in section 3 of the Act as: (i) the
specific areas within the geographical area occupied by a species, at
the time it is listed in accordance with the provisions of section 4 of
the Act, on which are found those physical or biological features (I)
essential to the conservation of the species and (II) that may require
special management considerations or protection, and (ii) specific
areas outside the geographical area occupied by a species at the time
it is listed, upon a determination by the Secretary that such areas are
essential for the conservation of the species (16 U.S.C. 1532(5)).
``Conservation'' means the use of all methods and procedures needed to
bring an endangered or threatened species to the point at which
protection under the Act is no longer necessary.
Due to the small number of populations, the mountain yellow-legged
frog is vulnerable to unrestricted collection, vandalism, or other
disturbance. We are concerned that these threats might be exacerbated
by the publication of critical habitat maps and further dissemination
of locational information. However, we have examined the evidence
available for the mountain yellow-legged frog and have not found
significant specific evidence of taking, vandalism, collection, or
trade of this species or any similarly situated species. Consequently,
consistent with applicable regulations (50 CFR 424.12(a)(1)(i)) and
recent case law, we do not expect that the identification of critical
habitat will increase the degree of threat to this species of taking or
other human activity.
In the absence of a finding that critical habitat would increase
threats to a species, if there are any benefits to critical habitat
designation, then a prudent finding is warranted. In the case of this
species, there may be some benefits to designation of critical habitat.
The primary regulatory effect of critical habitat is the section 7
requirement that Federal agencies refrain from taking any action that
destroys or adversely modifies critical habitat. While a critical
habitat designation for habitat currently occupied by this species
would not be likely to change the section 7 consultation outcome
because an action that destroys or adversely modifies such critical
habitat would also be likely to result in jeopardy to the species,
there may be instances where section 7 consultation would be triggered
only if critical habitat is designated. Examples could include
unoccupied habitat or occupied habitat that may become unoccupied in
the future. There may also be some educational or informational
benefits to designating critical habitat. Therefore, we find that
critical habitat is prudent for this DPS of the mountain yellow-legged
frog.
The Final Listing Priority Guidance for FY 2000 (64 FR 57114)
states, ``The processing of critical habitat determinations (prudency
and determinability decisions) and proposed or final designations of
critical habitat will be funded separately from other section 4 listing
actions and will no longer be subject to prioritization under the
Listing Priority Guidance. Critical habitat determinations, which were
previously included in final listing rules published in the Federal
Register, may now be processed separately, in which case stand-alone
critical habitat determinations will be published as notices in the
Federal Register. We will undertake critical habitat determinations and
designations during FY 2000 as allowed by our funding allocation for
that year.'' As explained in detail in the Listing Priority Guidance,
our listing budget is currently insufficient to allow us to immediately
complete all of the listing actions required by the Act. Deferral of
the critical habitat designation for this DPS of the mountain yellow-
legged frog will allow us to concentrate our limited resources on
higher priority critical habitat and other listing actions, while
allowing us to put in place protections needed for the conservation of
the mountain yellow-legged frog without further delay.
We plan to employ a priority system for deciding which outstanding
critical habitat designations should be addressed first. We will focus
our efforts on those designations that will provide the most
conservation benefit, taking into consideration the efficacy of
critical habitat designation in addressing the threats to the species,
and the magnitude and immediacy of those threats. We will develop a
proposal to designate critical habitat for this DPS of the mountain
yellow-legged frog as soon as feasible, considering our workload
priorities.
Available Conservation Measures
Conservation measures provided to species listed as endangered or
threatened under the Act include requirements for Federal protection,
prohibitions against certain practices, and recovery actions. The Act
provides for possible land acquisition/exchange and cooperation with
the States. The protection required of Federal agencies and the
prohibitions against certain activities involving listed species are
discussed, in part, below. Listing of the southern California DPS as
endangered will provide for the development of a recovery plan. Such a
plan will bring together both State and Federal efforts for the
mountain yellow-legged frog's conservation. The plan will establish a
framework for cooperation and coordination among agencies in
conservation efforts. The plan will set recovery priorities and
estimate costs of various tasks necessary to accomplish them. It will
also describe site-specific management actions necessary to achieve
conservation and survival of the southern California DPS of the
mountain yellow-legged frog.
Section 7(a) of the Act, as amended, 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 being designated. Regulations implementing this
interagency cooperation provision of the Act are codified at 50 CFR
part 402. Section 7(a)(4) requires Federal agencies to confer
informally with the Service on any action that is likely to jeopardize
the continued existence of a proposed species or result in destruction
or adverse modification of its proposed critical habitat. If a species
is listed subsequently, Section 7(a)(2) requires Federal agencies to
ensure that activities they authorize, fund, or carry out are not
likely to jeopardize the continued existence of such a species or to
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 agencies expected to have involvement with section 7
regarding the southern California DPS of mountain yellow-legged frog
include the U.S. Forest Service through its management activities and
the U.S. Army Corps of Engineers through its permit authority under
section 404 of the Clean Water Act. These agencies either administer
lands containing the DPS or authorize, fund, or otherwise conduct
activities that may affect the DPS.
The Act and implementing regulations found at 50 CFR 17.21 set
forth a series of general prohibitions and exceptions that apply to all
endangered wildlife. These prohibitions, in part,
[[Page 71721]]
make it illegal for any person subject to the jurisdiction of the
United States to take (including harass, harm, pursue, hunt, shoot,
wound, kill, trap, capture, collect, or attempt any such conduct),
import or export, transport in interstate or foreign commerce in the
course of commercial activity, or sell or offer for sale in interstate
or foreign commerce any listed species. 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.
It is the policy of the Service published in the Federal Register
on July 1, 1994 (59 FR 34272), to identify to the maximum extent
practical 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
listing on proposed and ongoing activities within a species' range. If
the DPS is eventually listed, we believe the following actions would
not be likely to result in a violation of section 9:
Possession, delivery, or movement, including interstate transport
and import into or export from the United States, involving no
commercial activity, of dead specimens of this taxa that were collected
prior to the date of publication in the Federal Register of the final
regulation adding this taxa to the list of endangered species.
Activities that the Service believes could potentially harm the
southern California DPS of mountain yellow-legged frog and result in a
violation of section 9 of the Act include, but are not limited to:
(1) Take of southern California mountain yellow-legged frogs
without a permit, which includes harassing, harming, pursuing, hunting,
shooting, wounding, killing, trapping, capturing, or collecting, or
attempting any of these actions;
(2) Possessing, selling, delivering, carrying, transporting, or
shipping illegally taken mountain yellow-legged frogs;
(3) Interstate and foreign commerce (commerce across State and
international boundaries) and import/export (as discussed earlier in
this section);
(4) Introduction of nonnative species that compete or hybridize
with, or prey on, mountain yellow-legged frogs; and
(5) Destruction or alteration of mountain yellow-legged frog
habitat by dredging, channelization, diversion, in-stream vehicle
operation or rock removal, or other activities that result in the
destruction or significant degradation of cover, channel stability,
substrate composition, temperature, and habitat used by the species for
foraging, cover, migration, and breeding; and
(6) Discharges or dumping of toxic chemicals, silt, or other
pollutants into waters supporting mountain yellow-legged frogs by
mining, or other developmental or land management activities that
result in destruction or significant degradation of cover, channel
stability, substrate composition, temperature, and habitat used by the
species for foraging, cover, migration, and breeding.
Questions regarding whether specific activities may constitute a
violation of section 9 should be directed to the Field Supervisor of
our Carlsbad Fish and Wildlife Office (see ADDRESSES section). Requests
for copies of the regulations and inquiries regarding them may be
addressed to the U.S. Fish and Wildlife Service, Ecological Services,
Endangered Species Permits, 911 Northeast 11th Avenue, Portland, Oregon
97232-4181 (503/231-6241; FAX 503/231-6243).
Permits may be issued to carry out otherwise prohibited activities
involving endangered wildlife species under certain circumstances.
Regulations governing these permits are at 50 CFR 17.22 and 17.23. Such
permits are available for scientific purposes, to enhance the
propagation or survival of the species, for incidental take in
connection with otherwise lawful activities, and/or for economic
hardship.
Public Comments Solicited
The Service intends that any final action resulting from this
proposal will be as accurate and as effective as possible. Therefore,
comments or suggestions from the public, other concerned governmental
agencies, the scientific community, industry, or any other interested
party concerning this proposed rule are hereby solicited. Comments
particularly are sought concerning:
(1) Biological, commercial trade, or other relevant data concerning
any threat (or lack thereof) to this species;
(2) The distribution of resident rainbow trout in the mountains of
southern California prior to the stocking programs of the California
Department of Fish and Game;
(3) The location of any additional occurrences of this species and
the reasons why any habitat should or should not be determined to be
critical habitat as provided by section 4 of the Act;
(4) Additional information concerning the range, distribution, and
population size of this species; and
(5) Current or planned activities in the subject area and their
possible impacts on the southern California population of mountain
yellow-legged frogs.
Final promulgation of the regulation(s) on this species will take
into consideration the comments and any additional information received
by the Service. Such communications may lead to a final regulation that
differs from this proposal.
The Endangered Species Act provides for one or more public hearings
on this proposal, if requested. Requests must be received within 45
days of the date of publication of the proposal in the Federal
Register. Such requests must be made in writing and addressed to
Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife
Office (see ADDRESSES section).
National Environmental Policy Act
The U.S. Fish and Wildlife Service has determined that
environmental assessments and environmental impact statements, as
defined under the authority of the National Environmental Policy Act of
1969, need not be prepared in connection with regulations adopted
pursuant to section 4(a) of the Endangered Species Act of 1973, as
amended. A notice outlining the Service's reasons for this
determination was published in the Federal Register on October 25, 1983
(48 FR 49244).
References Cited
A complete list of all references cited herein are available upon
request from the Carlsbad Field Office (see ADDRESSES above).
Author
The primary author of this document is Paul J. Barrett, Carlsbad
Fish and Wildlife Office (see ADDRESSES section).
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]
1. The authority citation for part 17 continues to read as follows:
Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C.
4201-4245; Pub. L. 99-625, 100 Stat. 3500, unless otherwise noted.
[[Page 71722]]
2. Section 17.11(h) is amended by adding the following, in
alphabetical order under AMPHIBIANS, to the List of Endangered and
Threatened Wildlife 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
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * * * *
Amphibians
* * * * * * *
Frog, mountain yellow-legged..... Rana muscosa........ U.S.A. (California, U.S.A., southern E ........... NA NA
Nevada) including California.
San Diego, Orange,
Riverside, San
Bernardino, and
Los Angeles
Counties.
* * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dated: December 10, 1999.
Jamie Rappaport Clark,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 99-33087 Filed 12-17-99; 11:48 am]
BILLING CODE 4310-55-P