[Federal Register: January 16, 2003 (Volume 68, Number 11)]
[Proposed Rules]               
[Page 2283-2303]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; 12-Month Finding 
for a Petition To List the Sierra Nevada Distinct Population Segment of 
the Mountain Yellow-legged Frog (Rana muscosa).

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding for a petition to list the Sierra Nevada distinct 
population segment of the mountain yellow-legged frog (Rana muscosa) 
under the Endangered Species Act of 1973, as amended. After review of 
all available scientific and commercial information, we find that the 
petitioned action is warranted, but precluded by higher priority 
actions to amend the Lists of Endangered and Threatened Wildlife and 
Plants. Upon publication of this 12-month petition finding, this 
species will be added to our candidate species list. We will develop a 
proposed rule to list this population pursuant to our Listing Priority 

DATES: The finding announced in this document was made on January 10, 
2003. Comments and information may be submitted until further notice.

ADDRESSES: You may send data, information, comments, or questions 
concerning this finding to the Field Supervisor (Attn: MYLF), 
Sacramento Fish and Wildlife Office, U.S. Fish and Wildlife Service, 
2800 Cottage Way, Room W-2605, Sacramento, California 95825. You may 
inspect the petition, administrative finding, supporting information, 
and comments received, during normal business hours by appointment, at 
the above address.

FOR FURTHER INFORMATION CONTACT: Peter Epanchin, Susan Moore, or Chris 
Nagano at the above address (telephone, (916) 414-6600; fax, (916) 414-



    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the List of Threatened and Endangered Species that contains 
substantial scientific and commercial information that listing may be 
warranted, we make a finding within 12 months of the date of the 
receipt of the petition on whether the petitioned action is: (a) Not 
warranted, or (b) warranted, or (c) warranted but that the immediate 
proposal of a regulation implementing the petitioned action is 
precluded by other pending proposals to determine whether any species 
is threatened or endangered, and expeditious progress is being made to 
add or remove qualified species from the List of Threatened and 
Endangered Species. Section 4(b)(3)(C) of the Act requires that a 
petition for which the requested action is found to be warranted but 
precluded shall be treated as though resubmitted on the date of such 
finding, i.e., requiring a subsequent finding to be made within 12 
months. Such 12-month findings are to be published promptly in the 
Federal Register.

[[Page 2284]]


    Camp (1917) described the mountain yellow-legged frog as two 
subspecies of Rana boylii: R. b. sierrae in the Sierra Nevada, and R. 
b. muscosa in southern California. On the basis of the similar 
morphological (body structure) characteristics of the two subspecies, 
the small number of sites where both were found, and breeding 
experiments, R. b. muscosa and R. b. sierrae were split from the R. 
boylii group and combined under a single species, R. muscosa (Zweifel 
1955). Genetic studies also have concluded that R. muscosa and R. 
boylii are distinct species (Case 1978; Davis 1986; Green 1986a, 1986b; 
Hillis and Davis 1986; Macey et al. 2001).


    The body length (snout to vent) of the mountain yellow-legged frog 
ranges from 40 to 80 millimeters (mm) (1.5 to 3.25 inches (in)) 
(Jennings and Hayes 1994). Females average slightly larger than males 
and males have a swollen, darkened thumb base (Wright and Wright 1949; 
Stebbins 1951; Zweifel 1955, 1968). Dorsal (upper) coloration in adults 
may be variable, exhibiting a mix of brown and yellow, but it also can 
be grey, red, or green-brown, and usually patterned with dark spots 
(Stebbins 1985; Jennings and Hayes 1994). These spots may be large (6 
mm (0.25 in)) and few, smaller and more numerous, or a mixture of both 
(Zweifel 1955). Irregular lichen or moss-like patches (to which the 
name muscosa refers) also may be present on the dorsal surface (Zweifel 
1955; Stebbins 1985). The belly and undersurfaces of the hind limbs are 
yellow or orange, and this pigmentation on the abdomen may extend 
forward to the forelimbs (Wright and Wright 1949; Stebbins 1985). This 
species may produce a distinctive mink or garlic-like odor when 
disturbed (Wright and Wright 1949; Stebbins 1985). Although the species 
lacks vocal sacks, it can make both terrestrial and underwater 
vocalizations, which have been described as a flat clicking sound 
(Zweifel 1955; Stebbins 1985; Ziesmer 1997). The mountain yellow-legged 
frog has smoother skin, generally heavier spotting and mottling 
dorsally, and darker toe tips than the foothill yellow-legged frog (R. 
boylii) (Zweifel 1955; Stebbins 1985).
    Eggs of the mountain yellow-legged frog are laid in globular 
clumps, which are often somewhat flattened, roughly 2.5 to 5 cm (1 to 2 
in) across (Stebbins 1985). When eggs are close to hatching, egg mass 
volume may average 198 cubic cm (78 cubic in) (Pope 1999a). Eggs have 
three firm jelly-like transparent envelopes surrounding a grey-tan or 
black vitelline (egg yolk) capsule (Wright and Wright 1949).
    The larvae (tadpoles) of this species generally are mottled brown 
in dorsal coloration with a golden tint and a faintly-yellow venter 
(underside) (Zweifel 1955; Stebbins 1985). Total tadpole length reaches 
72 mm (2.8 in), its body is flattened, and the tail musculature is 
wide, about 2.5 centimeters (cm) (1 in) or more, before tapering into a 
rounded tip (Wright and Wright 1949). The mouth has a maximum of 7 
labial (lip) tooth rows (2-3 upper and 4 lower) (Stebbins 1985). Larvae 
often take 2 to 4 years or more to reach metamorphosis (transformation 
from larvae to frogs) (Wright and Wright 1949; Cory 1962b; Bradford 
1983; Bradford et al. 1993; Knapp and Matthews 2000).


    The mountain yellow-legged frog is restricted to two disjunct areas 
in California and a portion of Nevada. One area is in the Sierra Nevada 
and the other area is in the San Gabriel, San Bernardino, and San 
Jacinto mountain ranges of southern California (Los Angeles, San 
Bernardino, Riverside, and San Diego counties) (Zweifel 1955; Jennings 
and Hayes 1994). The southern California population is isolated from 
the Sierra Nevada population by the Tehachapi mountain range, with a 
distance of about 225 kilometers (km) (140 miles (mi)) between the two 
    In the Sierra Nevada, the historic distribution of the mountain 
yellow-legged frog was more or less continuous from the vicinity of La 
Porte in southern Plumas County southward to Taylor and French Joe 
Meadows in southern Tulare County (Jennings and Hayes 1994). Records 
for this species in the Sierra Nevada document its occurrence on the 
east and west sides of the crest in all major drainages from Plumas to 
Tulare counties, with a single record from Kern County (Zweifel 1955; 
Jennings and Hayes 1994; Knapp 1996). Except for historic populations 
in extreme western Nevada in Washoe and Douglas counties, on Mt. Rose 
near Lake Tahoe, possibly Edgewood Creek, and elsewhere around Lake 
Tahoe, the species is confined to California (Zweifel 1955). The 
elevational range for the mountain yellow-legged frog in the Sierra 
Nevada ranges from approximately 1,370 meters (m) (4,500 feet (ft)) at 
San Antonio Creek, near Dorrington in Calaveras County, to over 3,650 m 
(12,000 ft) at Desolation Lake in Fresno County, though populations 
typically are encountered in the upper half of that elevation range 
(Zweifel 1955; Mullally and Cunningham 1956; Stebbins 1985).

Habitat Requirements

    Mountain yellow-legged frogs rarely are found more than 1 m (3.3 
ft) from water (Stebbins 1951; Mullally and Cunningham 1956; Bradford 
et al. 1993). At the lower elevations in the Sierra Nevada, the species 
usually is associated with rocky stream beds and wet meadows surrounded 
by coniferous forest (Zweifel 1955; Zeiner et al. 1988). At higher 
elevations, the species occupies lakes, ponds, tarns, and streams 
(Zweifel 1955; Mullally and Cunningham 1956; Stebbins 1985). The 
borders of alpine (above treeline) lakes and montane (mountain) meadow 
streams used by mountain yellow-legged frogs are frequently grassy or 
muddy; this differs from the sandy or rocky shores that are inhabited 
by the amphibian in lower elevation streams (Zweifel 1955). Adults 
typically are found sitting on rocks along the shoreline, usually where 
there is little or no vegetation (Mullally and Cunningham 1956). 
Although the species may use a variety of shoreline habitats, both 
larvae and adults are less common at shorelines which drop abruptly to 
a depth of 60 cm (2 ft) than at open shorelines that gently slope up to 
shallow waters of only 5-8 cm (2-3 in) deep (Mullally and Cunningham 
1956; Jennings and Hayes 1994). Mountain yellow-legged frogs also use 
stream habitats, especially in the northern part of their range. 
Streams utilized by adults vary from those having high gradients with 
numerous pools, rapids, and small waterfalls, to those with low 
gradients with slow flows, marshy edges, and sod banks (Zweifel 1955). 
Aquatic substrates vary from bedrock to fine sand, rubble (rock 
fragments), and boulders (Zweifel 1955). Mountain yellow-legged frogs 
seem to be absent from the smallest creeks, probably because these have 
insufficient depth for adequate refuge and overwintering habitat 
(Jennings and Hayes 1994).
    Both adults and larvae overwinter for up to 9 months in the bottoms 
of lakes that are at least 1.7 m (5.6 ft) deep; however, overwinter 
survival may be greater in lakes that are at least 2.5 m (8.2 ft) deep, 
under ledges of stream or lake banks, or in rocky streams (Bradford 
1983; V. Vredenburg et al. (in press)). In some instances, frogs have 
been found to overwinter in underwater bedrock crevices between 0.2 m 
(0.7 ft) and 1 m (3.3 ft) below the water surface (Matthews and Pope 
1999) and the use

[[Page 2285]]

of such crevices appears to allow them to survive in shallower water 
bodies that freeze to the bottom in winter (Pope 1999a). In lakes and 
ponds that do not freeze to the bottom in winter, mountain yellow-
legged frogs may overwinter in the shelter of bedrock crevices as a 
behavioral response to the presence of introduced fishes (V. Vredenburg 
et al. (in press)).
    Adult mountain yellow-legged frogs breed in the shallows of ponds 
or in inlet streams and are often seen on wet substrates within 1 m (3 
ft) of the water's edge (Zweifel 1955). Adults emerge from 
overwintering sites immediately following snowmelt and will move over 
ice to get to breeding sites (Pope 1999a; V. Vredenburg in litt. 2002). 
Mountain yellow-legged frogs in the Sierra Nevada deposit their eggs 
underwater in clusters, which they attach to rocks, gravel, vegetation, 
or under banks (Wright and Wright 1949; Stebbins 1951; Zweifel 1955; 
Pope 1999a). Clutch size varies from 15 to 350 eggs per egg mass 
(Livezey and Wright 1945; V. Vredenburg et al. (in press)). In 
laboratory breeding experiments, egg hatching times ranged from 18 to 
21 days at temperatures ranging from 5 to 13.5 Celsius ([deg]C ) (41 to 
56 Fahrenheit ([deg]F)) (Zweifel 1955). Field observations are similar 
(Pope 1999a).
    The time required to develop from fertilization to metamorphosis is 
believed to vary between 1 and 4 years (Storer 1925; Wright and Wright 
1949; Zweifel 1955; Cory 1962b; V. Vredenburg et al. (in press)). Since 
larvae must overwinter at least two or three times before 
metamorphosis, successful breeding sites are located in, or connected 
to, lakes and ponds that do not dry in the summer, and that are 
sufficiently deep so as to not completely freeze through in winter 
(Bradford 1983). Larval survival to metamorphosis is possible in lakes 
that do not dry out during the summer. Knapp and Matthews (2000) found 
the number of larvae was larger in fishless water bodies deeper than 2 
m (6.5 ft). Bradford (1983) found that mountain yellow-legged frog die-
offs sometimes result from oxygen depletion during winter in lakes less 
than 4 m (13 ft) deep. However, larvae may survive for months in nearly 
anoxic (oxygen-deficient) conditions when shallow lakes are frozen to 
the bottom. Recent studies have reported populations of mountain 
yellow-legged frogs overwintering in lakes less than 1.5 m (5 ft) deep 
that were assumed to have frozen to the bottom, and yet healthy frogs 
were documented to emerge the following July (Matthews and Pope 1999; 
Pope 1999a). Radio telemetry indicated that the mountain yellow-legged 
frogs were utilizing rock crevices near shore, crevices, holes, and 
ledges where water depths ranged from 0.2 m (0.7 ft) to 1.5 m (5 ft) 
(Matthews and Pope 1999). The granite surrounding these overwintering 
habitats may insulate the mountain yellow-legged frogs from the extreme 
winter temperatures, providing that there is an adequate supply of 
oxygen either in the water or air (Matthews and Pope 1999).
    Larvae maintain a relatively high body temperature by selecting 
warmer microhabitats (Bradford 1984). During winter, larvae remain in 
warmer water below the thermocline (thermally stratified water); after 
spring overturn (thaw and thermal mixing of the water), they continue 
to behaviorally modulate their body temperature by daily movements: 
during the day, larvae move to warm, shallow, nearshore water, and 
during the late afternoon and evening, they retreat to the warmer 
waters off shore (Bradford 1984).
    The time required to reach reproductive maturity is thought to vary 
between 3 and 4 years after metamorphosis (Zweifel 1955). Longevity of 
adults is unknown, but adult survivorship from year to year is very 
high, so they are undoubtedly long-lived amphibians (Matthews and Pope 
1999; Pope 1999a). Although data currently are limited, evidence exists 
that mountain yellow-legged frogs display strong site fidelity and 
return to the same overwintering and summer habitats from year to year 
(Pope 1999a).
    In aquatic habitats, mountain yellow-legged frog adults typically 
move only a few hundred meters (few hundred yards) (Matthews and Pope 
1999; Pope 1999a), but distances of up to 1 km (0.62 mi) have been 
recorded (V. Vredenburg et al. (in press)). Adults tend to move between 
selected breeding, feeding, and overwintering habitats during the 
course of the year. Though adults are typically found within 1 m (3.3 
ft) of water, overland movements of over 65 m (215 ft) have been 
recorded (Pope 1999a); the furthest reported distance of a mountain 
yellow-legged frog from water is 400 m (1,300 ft) (V. Vredenburg et al. 
(in press). Almost no data exist on the dispersal of juvenile mountain 
yellow-legged frogs away from breeding sites (Bradford 1991). However, 
juveniles that may be dispersing to permanent water have been observed 
in small intermittent streams (Bradford 1991). Mountain yellow-legged 
frog population dynamics are thought to have a metapopulation structure 
(Bradford et al. 1993; Drost and Fellers 1996; Knapp and Matthews 
2000). In describing the metapopulation concept, Hanski and Simberloff 
(1997) stated: ``* * *the two key premises in this approach to 
population biology are that populations are spatially structured in 
assemblages of local breeding populations and that migration among the 
local populations has some effect on local dynamics, including the 
possibility of population reestablishment following extinction.''
    Adult mountain yellow-legged frogs are thought to feed 
preferentially upon terrestrial insects and adult stages of aquatic 
insects while on the shore and in shallow water (Bradford 1983). 
Feeding studies on Sierra Nevada mountain yellow-legged frogs are 
limited. Remains found inside the stomachs of mountain yellow-legged 
frogs in southern California include a wide variety of invertebrates, 
including beetles, ants, bees, wasps, flies, true-bugs, and dragonflies 
(Long 1970). Larger frogs take more aquatic true bugs (insects in the 
taxonomic order Hemiptera) probably because of their more aquatic 
behavior (Jennings and Hayes 1994). Adult mountain yellow-legged frogs 
have been observed eating Yosemite toad (Bufo canorus) and Pacific 
treefrog (Pseudacris regilla) larvae (Mullally 1953; Zeiner et al. 
1988; Pope 1999b; Feldman and Wilkinson 2000) and can be cannibalistic 
(Heller 1960). Mountain yellow-legged frog larvae graze on benthic 
detritus, algae, and diatoms along rocky bottoms in streams, lakes, and 
ponds (Bradford 1983; Zeiner et al. 1988). Larvae have also been 
observed cannibalizing conspecific (of the same species) eggs 
(Vredenburg 2000). In addition, larvae have been seen feeding on the 
carcasses of dead metamorphosed frogs (V. Vredenburg et al. (in 


    The distribution of the Sierra Nevada mountain yellow-legged frog 
is restricted primarily to publicly managed lands at high elevations, 
including streams, lakes, ponds, and meadow wetlands located on 
national forests, including wilderness and non-wilderness on the 
forests, and national parks. Approximately 210 known mountain yellow-
legged frog populations (or populations within metapopulations) exist 
on the national forests within the Sierra Nevada, though not all of 
these populations may be reproducing successfully. In the national 
parks of the Sierra Nevada, there are 758 known sites with mountain 
yellow legged-frogs, most of which occur within 59 different basins 
that have multiple breeding populations that are connected 
hydrologially, so that populations in each basin function as

[[Page 2286]]

metapopulations). Within these 758 sites, 330 populations exist for 
which we have evidence of successful reproduction. Overall, we estimate 
that 22 percent of the remaining mountain yellow-legged frog sites 
within the Sierra Nevada are found within the national forests 
(including those with and those without evidence of successful 
reproduction), while 78 percent are found within the national parks 
(including those with and those without evidence of successful 
reproduction). These percentages represent the number of sites within 
the national forests and the national parks of the Sierra Nevada; they 
do not represent the number of individuals present at each site. The 
methods for measuring the numbers of populations and metapopulations in 
the national forests and the national parks have not been standardized 
and, therefore we must use caution when we compare national forests 
numbers to national park numbers. However, the remaining populations of 
mountain yellow-legged frogs are more numerous and larger in size in 
the national parks than in the national forests.
    National forests with extant populations of mountain yellow-legged 
frogs include the Plumas National Forest, Tahoe National Forest, 
Humboldt-Toiyabe National Forest, Lake Tahoe Basin Management Unit 
(managed by the U.S. Forest Service (USFS)), Eldorado National Forest, 
Stanislaus National Forest, Sierra National Forest, Sequoia National 
Forest, and Inyo National Forest. National parks with extant 
populations of mountain yellow-legged frogs include Yosemite National 
Park, Kings Canyon National Park, and Sequoia National Park.
    Grinnell and Storer (1924) first observed declines of mountain 
yellow-legged frog populations. Since then, a number of researchers 
have reported that the mountain yellow-legged frog has disappeared from 
a significant portion of its historic range in the Sierra Nevada (Hayes 
and Jennings 1986; Bradford 1989; Jennings and Hayes 1994; Bradford et 
al. 1994a; Jennings 1995, 1996; Stebbins and Cohen 1995; Drost and 
Fellers 1996; Knapp and Matthews 2000). The observed declines of 
mountain yellow-legged frog populations in the 1970s were small 
relative to the declines observed during the 1980s and 1990s. 
Rangewide, it is estimated that mountain yellow-legged frog populations 
have undergone a 50 to 80 percent reduction in size (Bradford et al. 
1994a; Jennings 1995; Stebbins and Cohen 1995; Drost and Fellers 1996; 
Jennings 1996; Knapp and Matthews 2000). The most pronounced declines 
have occurred north of Lake Tahoe in the northernmost 125 km (78 mi) 
portion of the range, and south of Sequoia and Kings Canyon National 
Parks in Tulare County in the southernmost 50 km (31 mi) portion, where 
only a few populations remain (Fellers 1994; Jennings and Hayes 1994). 
Based on available USFS survey and observation data, there appear to be 
very few or no known large populations north of the Plumas National 
    Mountain yellow-legged frogs historically occurred in Nevada on the 
slopes of Mount Rose in Washoe County and probably in the vicinity of 
Lake Tahoe in Douglas County (Linsdale 1940; Zweifel 1955; Jennings 
1984). In 1994 and 1995, mountain yellow-legged frog surveys were 
conducted by Panik (1995) at 54 sites in the Carson Range of Nevada and 
California, including eight historic locations; no mountain yellow-
legged frogs were observed. A few scattered and unconfirmed sightings 
were reported in Nevada in the late 1990s, but any populations 
remaining in this State are likely to be extremely small and the 
species is thought to be extirpated from Nevada (R. Panik, Western 
Nevada Community College, in litt., 2002).
    The number of extant populations of the mountain yellow-legged 
frogs in the Sierra Nevada is greatly reduced. Remaining populations 
are patchily scattered throughout nearly all their historic range 
(Jennings and Hayes 1994; Jennings 1995, 1996). At the northernmost 
portions of the range in Butte and Plumas counties, few populations 
have been seen or discovered since 1970 (Jennings and Hayes 1994). 
Declines have also been noted in the central and southern Sierra (Drost 
and Fellers 1996). In the southern Sierra Nevada (Sierra, Sequoia, and 
Inyo National Forests; and Sequoia, Kings Canyon, and Yosemite National 
Parks), there are relatively large populations (e.g., breeding 
populations of over 20 adults) of mountain yellow-legged frogs; 
however, in recent years, some of the largest of these populations have 
been extirpated (Bradford 1991; Bradford et al. 1994a; R. Knapp, Sierra 
Nevada Aquatic Research Laboratory, in litt. 2002). Mountain yellow-
legged frog populations are more numerous and larger in size in the 
national parks of the Sierra Nevada than in the surrounding USFS lands 
(Bradford et al. 1994a; Knapp and Matthews 2000).
    Between 1988 and 1991, Bradford et al. (1994a) resurveyed sites 
known historically (between 1955 and 1979) to have contained mountain 
yellow-legged frogs. They resurveyed 27 historic sites on the Kaweah 
River, a western watershed within Sequoia National Park, and did not 
detect mountain yellow-legged frogs at any of these locations. They 
resurveyed 21 historic sites within the Kern, Kings, and San Joaquin 
River watersheds in Sequoia and Kings Canyon National Parks, and 
detected mountain yellow-legged frogs at 11 of these sites. Frogs were 
detected at three locations out of 24 historic sites outside of Sequoia 
and Kings Canyon National Parks. Rangewide, their resurvey effort 
detected mountain yellow-legged frogs at 14 of 72 historic sites, 
representing an 80 percent population decline. On the basis of these 
results, Bradford et al. (1994a) estimated a 50 percent population 
decline in Sequoia and Kings Canyon National Parks, with more 
pronounced declines elsewhere in the mountain yellow-legged frog's 
    Drost and Fellers (1996) surveyed for mountain yellow-legged frogs 
at sites documented by Grinnell and Storer (1924) in the early part of 
the 20th Century. The frog was reported to be the most common amphibian 
where they surveyed in the Yosemite area (Grinnell and Storer 1924). 
Drost and Fellers (1996) repeated Grinnell and Storer's 1924 survey and 
reported mountain yellow-legged frog presence at only 2 of the 14 sites 
where this animal had been previously detected. These two positive 
sightings consisted of a single larva at one site and a single adult 
female at another site. Drost and Fellers (1996) identified and 
surveyed 17 additional sites with suitable mountain yellow-legged frog 
habitat, and these surveys resulted in the detection of three 
additional populations.
    For the 86 historically occupied mountain yellow-legged frog sites 
documented between 1915 and 1959 and resurveyed by Bradford et al. 
(1994a) and Drost and Fellers (1996), an 80 percent decline occurred in 
the number of historical frog populations. Of the 86 historic sites, 
only 16 remained occupied at the time of resurvey.
    Knapp and Matthews (2000) surveyed more than 1,700 high elevation 
(averaging 3,400 m (11,150 ft)) lakes and ponds in the Sierra National 
Forest's John Muir Wilderness Area and in Kings Canyon National Park, 
encompassing a total of approximately 100,000 hectares (ha) (247,000 
acres (ac)). They found a strong negative correlation between 
introduced trout and the distribution of mountain yellow-legged frogs. 
In the summer of 2002, Knapp (in litt. 2002) resurveyed 302 water 
bodies determined by 1995 to 1997 surveys to be occupied by mountain 
yellow-legged frogs, and

[[Page 2287]]

resurveyed 744 of over 1,400 sites where frogs were not previously 
detected. Knapp found no change in status at 59 percent of these sites, 
but found that 41 percent of the sites had gone extinct, while 8 
percent of previously unoccupied sites were colonized. These data 
indicate an extinction rate that is 5 to 6 times higher than the 
colonization rate within this study area. This high rate of extinction 
over a 5- to-7-year time frame suggests the species may become extinct 
within a few decades (assuming that the rate of extinction and 
recolonization observed over this time period accurately reflects the 
long-term rates). The documented extinctions appeared to occur 
nonrandomly across the landscape, are spatially clumped typically, and 
involve the disappearance of all or nearly all mountain yellow-legged 
frog populations in a watershed (R. Knapp in litt. 2002). The 
colonization sites also appeared to be nonrandomly distributed, 
occurring primarily in watersheds with large mountain yellow-legged 
frog populations (R. Knapp in litt. 2002).
    A recent review of the current status of 255 previously documented 
mountain yellow-legged frog locations (based on Jennings and Hayes 
(1994)) throughout its historic range concluded that 83 percent of 
these sites are no longer occupied by this species (Davidson et al. 
2002). Each national forest and national park is discussed individually 
    Lassen National Forest: Historically, mountain yellow-legged frogs 
occurred on the Lassen National Forest within multiple watersheds, 
including Butte Creek, the West Branch Feather River, and the Middle 
Fork Feather River (M. McFarland, in litt. 2002). The last confirmed 
mountain yellow-legged frog sighting on the Lassen National Forest was 
made in 1966 in the area of Snag Lake in the West Branch Feather River 
watershed. Since 1993, the Lassen National Forest has conducted or 
funded informal and formal systematic amphibian surveys to assess the 
relative distribution and abundance of amphibian species, including the 
mountain yellow-legged frog. On the Lassen National Forest, mountain 
yellow-legged frogs have not been detected or confirmed during any of 
these surveys (M. McFarland in litt. 2002).
    Plumas National Forest: Based on resurvey efforts, Jennings and 
Hayes (1994) noted that the mountain yellow-legged frog was extirpated 
at a number of locations in the Plumas National Forest. As survey 
efforts continue by the Plumas National Forest, more mountain yellow-
legged frog populations are being documented. However, most of the 
estimated 55 populations are small, consisting of only a few 
individuals (T. Hopkins, USFS, pers. comm., 2002). The species appears 
to have disappeared from a significant number of historic locations, 
and the abundance of the species at known sites appears to be quite 
    Tahoe National Forest: Mountain yellow-legged frogs were present 
historically throughout the Tahoe National Forest and the surrounding 
areas of Sierra, Nevada, and Placer counties. Jennings and Hayes (1994) 
conclude that, based on their re-surveys of historic locations, 1992, 
the species had been extirpated in a number of locations by 1992.
    The Tahoe National Forest has been conducting some amphibian 
surveys. Approximately four or five extant populations exist in which 
mountain yellow-legged frog breeding has been documented (A. Carlson, 
USFS, pers. comm. 2002). Extant mountain yellow-legged frog populations 
on the Tahoe National Forest have been observed in both stream and pond 
habitats. One extant breeding population inhabits an old mining tailing 
pond that has been restored naturally to a forested wetland condition 
with an abundance of bankside and emergent vegetation (A. Carlson, 
pers. comm. 2002). The largest Tahoe National Forest population 
observed in recent surveys consists of fewer than 10 individuals. The 
species appears to have disappeared from a significant number of 
historic locations within the Tahoe National Forest and is in low 
abundance where it still persists (A. Carlson, pers. comm. 2002).
    Lake Tahoe Basin Management Unit: Historic sightings of the 
mountain yellow-legged frog in the Lake Tahoe Basin Management Unit are 
numerous, indicating that the species was abundant in the Lake Tahoe 
area (J. Reiner, USFS, pers. comm. 2002). Today, only one known 
population of mountain yellow-legged frogs remains on this national 
forest, although in 1997, the USFS saw evidence of limited breeding in 
the Desolation Wilderness (J. Reiner, pers. comm. 2002; J. Reiner and 
M. Schlesinger, USFS, in litt. 2000). The known population is small, as 
some adults were seen in 1999 but were not detected during 2002 
surveys, though larvae were detected. The habitat at this site is a 
meadow and stream complex that is large (approximately 24 ha (60 ac)) 
and in good condition (J. Reiner, pers. comm. 2002).
    Humboldt-Toiyabe National Forest: Only the westernmost portion of 
the Humboldt-Toiyabe National Forest is within the historic range of 
the mountain yellow-legged frog (Stebbins 1985). A distributional map 
of mountain yellow-legged frogs produced by Jennings and Hayes (1994) 
indicates historic collections of this species within the Humboldt-
Toiyabe National Forest in California. Resurveys of locations where 
mountain yellow-legged frogs occurred indicate that the species had 
become extirpated by 1992 at a number of locations in Humboldt-Toiyabe 
National Forest (Jennings and Hayes 1994). Surveys in California are 
ongoing. Approximately four populations (all in California) exist on 
this national forest (C. Milliron, California Department of Fish and 
Game (CDFG), in litt. 2002; L. Murphy, USFS, pers. comm. 2002). Chytrid 
fungus (see Factor C, Disease, below) has been documented at one of 
these populations (C. Milliron, in litt. 2002).
    Eldorado National Forest: The mountain yellow-legged frog is 
distributed across the Eldorado National Forest with populations or 
metapopulations (multiple breeding populations within the same basin 
that have hydrologic connectivity between them) within the headwaters 
and headwater tributaries of several watersheds, including the Rubicon 
River, the South Fork American River, the North Fork Cosumnes River, 
and the North Fork Mokelumne River (J. Williams, USFS, in litt. 2002).
    Numerous surveys for mountain yellow-legged frogs have been 
conducted on this national forest by the USFS, the CDFG, and several 
contractors between 1990 and 2002. Reproducing populations have been 
found at a variety of locations in high elevation areas of this 
national forest. Surveys for amphibians within the Eldorado National 
Forest in 1992 resulted in no detections of mountain yellow-legged 
frogs, though this may be a function of the limited area and habitat 
type that was surveyed (Martin 1992). Jennings and Hayes (1994) 
indicate both extirpated populations and extant populations on the 
Eldorado National Forest. Intensive surveys by CDFG and USFS in 2001 
and 2002 resulted in an estimated 18 extant populations or 
metapopulations of mountain yellow-legged frogs on the Eldorado 
National Forest, although both the mean number of populations and 
population size are generally low relative to historic reports (J. 
Williams, in litt. 2002). Currently, approximately four populations 
exist with between 25 and 50 mountain yellow-legged frogs; these are 
the largest populations on the Eldorado National Forest (J. Williams, 
in litt. 2002).

[[Page 2288]]

    Stanislaus National Forest: A 1992 survey (Martin 1992) in the 
Stanislaus National Forest located mountain yellow-legged frogs at only 
2 of 16 locations surveyed, and at these locations, the numbers of 
adults detected were small (under five). Jennings and Hayes (1994) 
indicate that the species has been extirpated from a number of historic 
locations. There are approximately 80 extant populations of mountain 
yellow-legged frogs on the Stanislaus National Forest; of these, only 
about 8 appear to have more than 10 adults, and only 2 populations are 
known to have 25 to 30 adults (L. Conway, USFS, pers. comm. 2002).
    Yosemite National Park: From 1914 to 1920, Grinnell and Storer 
conducted a biological survey along a transect across the Sierra 
Nevada. They documented mountain yellow-legged frogs at 14 sites 
throughout Yosemite National Park and noted the species was abundant in 
this area. Numerous frogs were found in lakes and streams at high 
elevations (Grinell and Storer 1924). ``Hundreds of frogs'' were found 
at Young Lake and frogs were ``very numerous'' at Westfall Meadow 
(Camp1915, as cited in Drost and Fellers 1994). Large numbers of 
specimens were collected; for example, 25 were taken at Vogelsang Lake 
(Grinnell 1915, as cited in Drost and Fellers 1994).
    The mountain yellow-legged frog was documented at several 
additional locations in Yosemite National Park from 1957 to 1960 
(Heller 1960). At Johnson Lake, Mullally and Cunningham (1956) reported 
a mountain yellow-legged frog population decline between 1950 and 1955, 
though they did not quantify the decline. They attributed this decline 
to the unusually long and cold winter of 1951-1952. Some of Yosemite's 
``densest aggregations of frogs ever noted'' by Mullally and Cunningham 
(1956) were in lakes near Ostrander Lake south of Glacier Point; they 
attributed the absence of frogs in Ostrander Lake to the presence of 
non-native trout.
    Between 1988 and 1991, Bradford et al. (1994a) randomly selected 
and surveyed four mountain yellow-legged frog populations documented in 
Yosemite between 1955 to 1979. Although they did not resurvey all of 
the mountain yellow-legged frog populations previously reported from 
within the park, they reported that the four resurveyed populations 
were extirpated (Bradford et al.1994a). In 1992 and 1993, Drost and 
Fellers (1996) revisited 38 of the original 40 sites surveyed by 
Grinnell and Storer from 1914 to1920, and surveyed other sites with 
potential mountain yellow-legged frog habitat. The mountain yellow-
legged frog had declined by approximately 80 percent from the locations 
documented by the 1924 study (Drost and Fellers 1996). A distribution 
map of mountain yellow-legged frogs produced by Jennings and Hayes 
(1994) also documents extinctions and indicates a population decline of 
this species from Yosemite National Park. Colwell and Beatty (2002) 
surveyed 35 lakes with appropriate mountain yellow-legged frog habitat 
within the Tuolumne and Merced River drainages of Yosemite National 
Park in 1992 and 1993; only 3 lakes were found to have mountain yellow-
legged frogs.
    Currently in Yosemite National Park, 251 mountain yellow-legged 
frog sites exist, most of which occur within 23 different basins that 
have multiple breeding populations with habitat that is connected 
hydrologically, so that the populations in each basin function as a 
metapopulation (R. Knapp in litt. 2002). Six sites have populations 
with over 100 adult mountain yellow-legged frogs each, 1 site has a 
population with between 51 and 100 adults, and 41 sites have 
populations between 10 and 50 adults each. In addition, 203 sites have 
fewer than 10 adults each. Of the 251 mountain-yellow legged frog sites 
in the park, evidence of breeding has been found in 71 populations.
    Inyo National Forest: Jennings and Hayes (1994) document the 
extirpation of some mountain yellow-legged frog populations from the 
Inyo National Forest. In 1994, 15 known locations had mountain yellow-
legged frog populations (Parker 1994). Currently, 7 basins within the 
Inyo National Forest have known extant mountain yellow-legged frog 
populations or populations that function as metapopulations (C. 
Milliron, in litt. 2002). Some of these populations are stable, 
consisting of several hundred individuals representing all age classes 
(L. Sims, USFS, in litt. 2002). Chytrid fungus (see Factor C, Disease, 
below) has been documented at an additional population location that is 
now extinct (C. Milliron, in litt. 2002).
    Sierra National Forest: In 1955, Mullally and Cunningham (1956) 
reported encountering mountain yellow-legged frogs along Paiute Creek 
``very sparingly'' at approximately 2,300 m (7,700 ft), with frogs 
becoming more abundant at higher elevations. The ``densest 
populations'' were found above 3,050 m (10,000 ft) in the Humphrey's 
Basin area, and a ``great many, including tadpoles'' were noted at and 
near Pine Creek Pass, with frogs also seen at Golden Trout and 
Desolation Lakes.
    Jennings and Hayes (1994) indicated that the mountain yellow-legged 
frog has become extirpated at a number of historical locations in the 
Sierra National Forest. Knapp and Matthews (2000) report on mountain 
yellow-legged frog population declines associated with fish stocking 
within the John Muir Wilderness Area of the Sierra National Forest (see 
Factor C, Disease, below). In 1995 and 1996, Knapp and Matthews (2000) 
surveyed 669 lakes, ponds, and other water bodies in the John Muir 
Wilderness Area. Mountain yellow-legged frog adults were found in 4 
percent of these water bodies, and frog larvae in 3 percent (Knapp and 
Mathews 2000). In 2002, Knapp conducted resurveys at the 28 water 
bodies that had been occupied by mountain yellow-legged frogs in 1997, 
and also at 118 of the 641 sites where frogs were not detected in 1997. 
Knapp found no change in mountain yellow-legged frog status at 39 
percent of these 28 previously occupied water bodies, but found that 
the frogs at 61 percent of the 28 previously occupied sites had gone 
extinct, while colonization had occurred at 10 percent of 118 
previously unoccupied sites (R. Knapp in litt. 2002).
    Although not all potential mountain yellow-legged frog habitats 
have been surveyed within the Sierra National Forest, approximately six 
subwatersheds have extant metapopulations (H. Eddinger, USFS, in litt. 
2002). These subwatersheds are in the upper headwaters of the South 
Fork Merced River, South Fork San Joaquin River, and North Fork Kings 
River. They include the Mono Creek Basin, the Bear Creek Basin, the 
Paiute Creek Basin, the Humphreys Creek Basin, the Big Creek Basin, and 
the Dinkey Creek Basin.
    Sequoia and Kings Canyon National Parks: Relatively few records 
exist for mountain yellow-legged frog prior to 1955 in the Sequoia and 
Kings Canyon National Parks. From 1955 to 1979, the species is known to 
have occurred in at least 21 sites scattered throughout Sequoia and 
Kings Canyon National Parks, although historic abundance is not known 
(Bradford et al. 1994a). In 1978-1979, the headwaters of seven creek 
systems were surveyed for mountain yellow-legged frogs in the national 
parks. Frogs were found at 27 sites greater than 200 m (660 ft) apart 
(Bradford et al. 1994a). A distributional map of mountain yellow-legged 
frogs produced by Jennings and Hayes (1994) indicates numerous historic 
sightings and collections of the species within both national parks, as 
well as numerous extinctions. The species was already noted to have 
disappeared from

[[Page 2289]]

approximately half of previously occupied locations in Sequoia and 
Kings Canyon Parks by the late 1980s (Bradford et al. 1994a). On the 
basis of surveys, Bradford et al. (1994a) estimate that mountain 
yellow-legged frogs have been extirpated from half of their historic 
locations in Sequoia and Kings Canyon National Parks. For example, 
Fellers (1994) surveyed in Sequoia and Kings Canyon National Parks and 
did not detect the mountain yellow-legged frog in the Kaweah watershed 
where the species was located historically.
    In 1997, Knapp and Matthews (2000) surveyed 1,059 lakes, ponds, and 
other water bodies in Kings Canyon National Park. Mountain yellow-
legged frog adults were found in 31 percent of these water bodies, and 
frog larvae in 20 percent (Knapp and Mathews 2000). Some significant 
frog populations remain in Sequoia and Kings Canyon National Parks, but 
extensive declines have been described. In 2002, Knapp (in litt. 2002) 
resurveyed 274 water bodies occupied by mountain yellow-legged frogs in 
1997, and he also resurveyed 626 of the 785 sites where frogs were not 
detected in 1997. Knapp found no change in status at 60 percent of the 
274 previously occupied sites, but found that 39 percent of the 274 
previously occupied sites had gone extinct, while colonization had 
occurred at 7 percent of 626 previously unoccupied sites.
    Currently in Sequoia and Kings Canyon National Parks, 507 mountain 
yellow-legged frog sites are known, most of which occur within 36 
different basins that have multiple breeding populations that are 
hydrologically connected, so that the populations within each basin 
function as a metapopulation. Fifty-four sites have populations of more 
than 100 adult mountain yellow-legged frogs, 25 sites have populations 
between 51 and 100 adults, 132 sites have populations between 10 and 50 
adults, and 296 sites have fewer than 10 adults. Of the 507 mountain 
yellow-legged frog sites in Sequoia and Kings Canyon National Parks, 
breeding evidence has been found at 259 populations (R. Knapp in litt. 
    Sequoia National Forest: Jennings and Hayes (1994) indicate that 
the mountain yellow-legged frog has been extirpated from a number of 
historical locations in the Sequoia National Forest. Mountain yellow-
legged frogs were collected on several historic locations of the Kern 
Plateau in Sequoia National Forest (Jennings and Hayes 1994). Today, 
two known extant populations exist on the Sequoia National Forest (S. 
Anderson, USFS, in litt. 2002).
    All of the recent mountain yellow-legged frog sightings from the 
Sequoia National Forest have been of single frogs or very small 
populations. In 1992, mountain yellow-legged frogs were not detected 
during amphibian surveys conducted at 17 sites in Sequoia National 
Forest (Martin 1992). The species appears to be severely reduced in 
numbers and range in the Sequoia National Forest.

Distinct Vertebrate Population Segment

    Under the Act, we must consider for listing any species, 
subspecies, or, for vertebrates, any distinct population segment (DPS) 
of these taxa if there is sufficient information to indicate that such 
action may be warranted. To implement the measures prescribed by the 
Act, we, along with the National Marine Fisheries Service (National 
Oceanic and Atmospheric Administration-Fisheries), developed a joint 
policy that addresses the recognition of DPSs for potential listing 
actions (61 FR 4722). The policy allows for a more refined application 
of the Act that better reflects the biological needs of the taxon being 
considered, and avoids the inclusion of entities that do not require 
the Act's protective measures.
    Under our DPS Policy, we use two elements to assess whether a 
population segment under consideration for listing may be recognized as 
a DPS. The elements are: (1) the population segment's discreteness from 
the remainder of the species to which it belongs; and (2) the 
significance of the population segment to the species to which it 
belongs. If we determine that a population segment being considered for 
listing is a DPS, then the level of threat to the population is 
evaluated based on the five listing factors established by the Act to 
determine if listing it as either threatened or endangered is 
    Discreteness. Under our DPS Policy, a population segment of a 
vertebrate species may be considered discrete if it satisfies either 
one of the following two conditions: (1) it is markedly separated from 
other populations of the same taxon as a consequence of physical, 
physiological, ecological, or behavioral factors. Quantitative measures 
of genetic or morphological discontinuity may provide evidence of this 
separation; or (2) it is delimited by international governmental 
boundaries within which significant differences in control of 
exploitation, management of habitat, conservation, status, or 
regulatory mechanisms exist. The proposed DPS, the Sierra Nevada 
mountain yellow-legged frog, is based on the first condition, the 
marked separation from other populations.
    The range of the mountain yellow-legged frog is divided by a 
natural geographic barrier, the Tehachapi Mountains, which 
geographically isolates the populations in the southern Sierra Nevada 
from those in the mountains of southern California. The distance of the 
geographic separation is about 225 km (140 mi). The geographic 
separation of the Sierra Nevada and southern California mountain 
yellow-legged frogs was recognized in the earliest description of the 
species by Camp (1917), who treated specimens from the two areas as 
separate subspecies of R. boylii. Camp (1917) described the two 
subspecies based on differences in their biogeography and morphology.
    Ziesmer (1997) analyzed vocalizations of mountain yellow-legged 
frogs from 86 locations in Alpine and Mariposa counties in the Sierra 
Nevada, and vocalizations of mountain yellow-legged frogs from 23 
locations in the San Jacinto Mountains of Riverside County in southern 
California. The vocalizations of Sierra Nevada frogs differed from 
those of southern California frogs in pulse rate, harmonic structure, 
and dominant frequency. Ziesmer (1997) concluded that the differences 
in vocalization supported the hypothesis that mountain yellow-legged 
frogs from the Sierra Nevada and southern California may represent 
separate species.
    Genetic analyses support the discreteness of the mountain yellow-
legged frog populations in southern California from those in the Sierra 
Nevada. In an allozyme (genetic) study that compared mountain yellow-
legged frogs from the central Sierra Nevada with those from southern 
California, a fairly significant genetic difference was found between 
the two populations (D. Green, McGill University, in litt. 1993). 
However, because there were no frog samples from the southern Sierra 
Nevada for comparison, it was not clear whether the difference 
reflected two ends of a cline (a character gradient), or distinctions 
between the Sierra Nevada and southern California populations. Thus, 
because the data set was incomplete, Green (in litt., 1993) interpreted 
the results cautiously.
    A phylogenetic analysis of mitochondrial deoxyribonucleic acid 
(DNA) sequences of the mountain yellow-legged frog was performed 
throughout its distribution (Macey et al. 2001). This study concluded 
that there are two major genetic lineages of the mountain yellow-legged 
frog (inclusive of the Sierra Nevada populations and

[[Page 2290]]

the southern California populations), with populations in the Sierra 
Nevada falling into three distinct groups and the fourth being the 
southern California population (Macey et al. 2001). Though three 
genetic lineages of mountain yellow-legged frogs have been identified 
in the Sierra Nevada, more genetic sampling is needed to delineate 
specific boundaries of the three genetic lineages before they are 
treated or managed as separate units (Macey et al. 2001). Therefore, 
this finding treats the three genetic lineages of the mountain yellow-
legged frog in the Sierra Nevada as one DPS, discrete from the mountain 
yellow-legged frog DPS in southern California.
    The biogeographic fragmentation within the Sierra Nevada population 
of mountain yellow-legged frogs occurs between Kings Canyon National 
Park and a region slightly north of Yosemite National Park, allowing 
for the central and northern Sierra Nevada populations to share more 
genetic similarities than the southern Sierra Nevada and southern 
California populations (Macey et al. 2001). In fact, this study 
indicates that the southern Sierran group (largely in Fresno County) 
may be more closely related to the southern California mountain yellow-
legged frogs than with those in the central and northern Sierra Nevada 
(Macey et al. 2001). This research suggests that the initial divergence 
between the northern and southern populations of mountain yellow-legged 
frogs occurred 2.2 million years before present. Within each of these 
groups, Macey et al. (2001) have detected a similar pattern of 
divergence that suggests the northern Sierra Nevada and central Sierra 
Nevada mountain yellow-legged frog populations diverged 1.5 million 
years before present, and the southern Sierra Nevada and the southern 
California mountain yellow-legged frog populations diverged from each 
other approximately 1.4 million years before present. Today, these 4 
groups are isolated by arid valleys; this isolation is most pronounced 
between southern California and the southern Sierra Nevada. The 
biogeographic pattern of genetic divergence as detected in the mountain 
yellow-legged frogs of the Sierra Nevada has also been observed in four 
other reptiles and amphibians, suggesting a common event that 
fragmented their ranges (Macey et al. 2001).
    Sierran frogs and southern California mountain yellow-legged frogs 
also differ ecologically in the types of aquatic habitat they occupy. 
Mountain yellow-legged frogs in southern California are typically found 
in steep gradient streams, even though they may range into small meadow 
streams at higher elevations (Zweifel 1955; Mullally 1959). In 
contrast, Sierran frogs are most abundant in high-elevation lakes and 
slow-moving portions of streams (Zweifel 1955; Mullally and Cunningham 
1956), habitat that is distinct from the canyons of southern 
California's arid mountain ranges, which are inhabited by the southern 
California DPS of the mountain yellow-legged frog.
    Significance. Under our DPS Policy, once we have determined that a 
population segment is discrete, we consider its biological and 
ecological significance to the larger taxon to which it belongs. This 
consideration may include, but is not limited to: (1) Evidence of the 
persistence of the discrete population segment in an ecological setting 
that is unusual or unique for the taxon; (2) evidence that loss of the 
population segment would result in a significant gap in the range of 
the taxon; (3) evidence that the population segment represents the only 
surviving natural occurrence of a taxon that may be more abundant 
elsewhere as an introduced population outside its historic range; or 
(4) evidence that the discrete population segment differs markedly from 
other populations of the species in its genetic characteristics.
    We have found substantial evidence that all but one (there are no 
introduced populations of mountain yellow-legged frogs outside of its 
historic range) of these significant factors are met by the population 
of mountain yellow-legged frogs in the Sierra Nevada. Furthermore, it 
is significant because a major reduction in abundance of the species as 
a whole would occur if the Sierra Nevada population were extirpated. 
The extinction of the Sierra Nevada population of the mountain yellow-
legged frog would result in the loss of a genetic entity, a reduction 
in the geographic range of the species, a loss of the species 
persistence in a setting ecologically unique relative to the ecological 
setting of the southern California population, and a reduction in the 
number of breeding populations. As discussed above, the Sierra Nevada 
population appears to be genetically distinct from the southern 
California population of mountain yellow-legged frogs. The mountain 
yellow-legged frogs of the Sierra Nevada comprise the main distribution 
of the species at the northern and central limits of the species' 
range. Loss of the Sierra Nevada population would be significant as it 
would eliminate the species from the majority of its range and would 
reduce the species to fewer than 10 small isolated sites in southern 
California (50 FR 44382). The geographic isolation of the Sierra Nevada 
population from the mountain yellow-legged frogs in southern California 
prevents genetic interchange between these populations.
    Conclusion. We evaluated the Sierra Nevada population of the 
mountain yellow-legged frog to determine whether it meets the 
definition of a DPS, addressing discreteness and significance as 
required by our policy. We conclude that the Sierra Nevada population 
of the mountain yellow-legged frog is discrete from the southern 
California population, on the basis of their geographic separation, 
differences in vocalization, differences between their habitats, and 
apparent genetic differences. We conclude that the Sierra Nevada 
population of the mountain yellow-legged frog is significant because 
the loss of the species from the Sierra Nevada would result in a 
significant reduction in the species' range and its population numbers, 
and would constitute the loss of a genetically discrete population that 
differs markedly from the southern California population of mountain 
yellow-legged frogs. Because the population segment meets both the 
discreteness and significance criteria of our DPS policy, the Sierra 
Nevada portion of the mountain yellow-legged frog's range qualifies for 
consideration for listing. An evaluation of the level of threat to the 
DPS based on the five listing factors established by the Act follows.

Previous Federal Action

    On February 10, 2000, we received a petition, dated February 8, 
2000, from the Center for Biological Diversity and Pacific Rivers 
Council to list the Sierra Nevada population of the mountain yellow-
legged frog as endangered. The petitioners stated that the Sierra 
Nevada population of the mountain yellow-legged frog qualifies for 
listing under our DPS Policy. On October 12, 2000, we published a 90-
day finding on that petition in the Federal Register (65 FR 60603) 
concluding that the petition presented substantial scientific or 
commercial information to indicate that the listing of the Sierra 
Nevada population of the mountain yellow-legged frog may be warranted; 
we also requested information and data regarding the species.
    This 12-month finding is made in accordance with a court order 
which requires us to complete a finding by January 10, 2003 (Center for 
Biological Diversity and Pacific Rivers Council v. Norton and Jones) 
(No. C 01-2106 SC). This notice constitutes the 12-month finding for 
the February 10, 2000, petition.

[[Page 2291]]

Summary of Factors Affecting the Species

    Section 4 of the Act and regulations (50 CFR part 424) promulgated 
to implement the listing provisions of the Act describe the procedures 
for adding species to the Federal lists. We may determine a species 
(which is defined in section 3 of the Act as including any subspecies 
of fish or wildlife or plants, and any distinct population segment of 
any species of vertebrate fish or wildlife which interbreeds when 
mature) to be endangered or threatened because of one or more of the 
five factors described in section 4(a)(1) of the Act. These factors, 
and their application to the Sierra Nevada DPS of the mountain yellow-
legged frog (mountain yellow-legged frog), are as follows:
    A. The present or threatened destruction, modification, or 
curtailment of its habitat or range. A number of hypotheses, including 
habitat loss, have been proposed for recent global amphibian declines 
(Bradford et al. 1993; Corn 1994; Alford and Richards 1999). Habitat 
destruction, however, does not appear to be the primary factor leading 
to the decline of the mountain yellow-legged frog. The mountain yellow-
legged frog occurs at high elevations in the Sierra Nevada, which have 
not had the types or extent of large-scale habitat conversion and 
disturbances which have occurred at lower elevations (Bradford et al. 
1993; Knapp 1996; Knapp and Matthews 2000). Large scale habitat 
conversion has not been identified within the range of this species; 
thus, direct habitat destruction or modification associated with 
intensive human activities, as measured by urban or agricultural land 
use within the mountain yellow-legged frogs' range, has not been 
implicated in the decline of this species (Davidson et al. 2002). 
However, other human activities have played a role in the modification 
of mountain yellow-legged frog habitat. These include livestock 
grazing, non-native fish introductions (see Predation, Factor C, 
below), timber management, road construction and maintenance, 
recreation, water diversions, fire management activities, and 
introduction of environmental contaminants (see Other, Factor E, 
below). These activities have modified habitat in ways that have 
fragmented and isolated mountain yellow-legged frog populations, and 
thereby, may have caused or contributed to the decline of this DPS 
(Bradford et al. 1993).


    Grazing of livestock in Sierra Nevada meadows and riparian areas 
(aquatic ecosystems and adjacent upland areas that directly affect 
them) began in the mid-1700s with the European settlement of California 
(Menke et al. 1996). Following the gold rush of the mid-1800s, grazing 
rose to a level that exceeded the carrying capacity of the available 
range and caused significant impacts to meadow and riparian ecosystems 
(Meehan and Platts 1978; Menke et al. 1996). From 1870 to 1908, within 
the range of the mountain yellow-legged frog in the high Sierra Nevada, 
meadows were converted to summer rangelands for grazing cattle, sheep, 
horses, goats, and in some areas pigs; however, the alpine areas were 
mainly grazed by sheep (Beesley 1996; Menke et al. 1996). This practice 
resulted in the degradation of these extremely sensitive areas (Menke 
et al. 1996).
    In general, livestock grazing within the range of the mountain 
yellow-legged frog was at a high but undocumented level until the 
establishment of national parks (beginning in 1890) and national 
forests (beginning in 1905). Within established national parks, grazing 
by cattle and sheep was replaced by that of packstock, such as horses 
and burros. Within established national forests, the amount of 
livestock grazing was gradually reduced and better documented, and the 
types of animals shifted, with reductions in sheep and increases in 
cattle and packstock. In general, livestock grazing within the national 
forests has continued with gradual reductions since the 1920s, except 
for an increase during World War II. Continuing decreases, motivated by 
concern towards resource protection, conflicts with other uses, and 
deteriorating range conditions, continued from the 1950s through the 
early 1970s but still exceeded sustainable grazing capacity in many 
areas (Menke et al. 1996; University of California (UC) 1996a). Grazing 
management that is more sensitive to riparian areas has been 
implemented and continues to increase since the 1970s (UC 1996a).
    Packstock grazing is the only grazing currently permitted in the 
Sierra Nevada national parks. Packstock grazing also is permitted in 
national forests within the Sierra Nevada. However, there has been very 
little monitoring of the impacts of packstock use in this region (Menke 
et al. 1996). Use of packstock in the Sierra Nevada increased since 
World War II as a result of increased road access and increases in 
leisure time and disposable income (Menke et al. 1996). Demand for 
packstock use and recreational riding in the Sierra Nevada are 
projected to increase as California's human population increases (USFS 
    Observational data indicate livestock negatively impact mountain 
yellow-legged frog populations by altering frog habitat and trampling 
individuals (R. Knapp, in litt. 1993a, 1993b, 1994, 2002; Jennings 
1996; A. Carlson, pers. comm. 2002; USFS 2002; V. Vrendenburg, in litt. 
    Livestock grazing causes changes in wetland systems, including 
meadows, streams, and ponds; modifies mountain yellow-legged frog 
habitat by removing overhanging banks that provide shelter; and 
contributes to the siltation of breeding ponds. Pond siltation may 
decrease the survivorship of overwintering larvae, subadults, and adult 
mountain yellow-legged frogs as the overwintering habitats need to be 
deep enough so that the entire water column does not freeze and 
underwater caves and crevices are available (Bradford 1983; Pope 
    Grazing of livestock in riparian areas impacts vegetation in 
multiple ways, including: soil compaction, which increases runoff and 
decreases water availability to plants; herbage removal, which promotes 
increased soil temperatures and evaporation rates at the soil surface; 
and direct physical damage to the vegetation (Kauffman and Krueger 
1984; Cole and Landres 1996; Knapp and Matthews 1996). Streamside 
vegetation protects and stabilizes streambanks by binding soils to 
resist erosion and to trap sediment (Chaney et al. 1990). A study by 
Kauffman et al. (1983) indicated that livestock grazing may have 
weakened the streambank structure through trampling and removal of 
vegetation, thereby promoting conditions for erosion. Removal of 
vegetative cover within mountain yellow-legged frog habitat decreases 
available habitat, exposes frogs to predation (R. Knapp, in litt. 
1993b), and increases the threat of dessication (Jennings 1996). 
Grazing may result in changes to vegetation composition, resulting in 
an increased density of forested stands and the expansion of trees into 
areas that were formerly treeless (Cole and Landres 1996).
    Livestock grazing can cause a nutrient loading problem due to 
urination and defecation in or near the water, and can elevate bacteria 
levels in areas where cattle are concentrated near water (Meehan and 
Platts 1978; Stephenson and Street 1978; Kauffman and Krueger 1984). 
The nutrient status of streams can markedly influence the growth of 
microflora and microfauna and directly and indirectly affect many other 
characteristics of the stream biota

[[Page 2292]]

(Lemly 1998). Growth of filamentous bacteria on the bodies and gills of 
aquatic insects has been documented in association with nutrient 
loading in livestock use pastures, along with significantly lower 
densities of insects at downstream sites. In laboratory and field 
studies, aquatic insects with this bacterial growth experienced 
extensive mortality. This indicates that elevated bacteria levels 
associated with livestock use can negatively influence stream insect 
populations (Lemley 1998). Adverse effects to aquatic insects within 
the range of the mountain yellow-legged frog could result in a lowered 
prey availability, possibly increasing intraspecific competition for 
limited resources.
    Throughout the range of the mountain yellow-legged frog in the 
Sierra Nevada approximately 79 currently active grazing allotments 
exist on USFS-administered lands. Of these grazing allotments, at least 
29 have extant mountain yellow-legged frog populations within them. An 
estimated 13 percent of the approximately 210 known mountain yellow-
legged frog populations, or populations that function as 
metapopulations, on Sierra Nevada national forests occur within active 
grazing allotments. Many of the mountain yellow-legged frog populations 
in the Sierra Nevada that occur within active grazing allotments are 
small. These populations may be more vulnerable to extirpation as a 
result of grazing-induced habitat modification, and if extirpated they 
might not be recolonized in situations where they are isolated from 
other populations and lack habitat connectivity to potential source 
    In the 60-Lakes Basin of Kings Canyon National Park, packstock use 
is regulated in wet meadows to protect mountain yellow-legged frog 
breeding habitat in bogs and lakeshores from trampling and associated 
degradation (V. Vredenburg, in litt. 2002; H. Werner, NPS, in litt. 


    Recreation is the fastest growing use of national forests. As such, 
its impacts on the mountain yellow-legged frog are likely to continue 
and to increase (USDA 2001). Recreational activities take place 
throughout the Sierra Nevada and have significant negative impacts on 
several plant and animal species and their habitats (USDA 2001a). To 
further recreational opportunities and angling success, non-native 
trout stocking programs in the Sierra Nevada started in the late 19th 
Century (Bahls 1992; Pister 2001). Trout stocking throughout the range 
of the mountain yellow-legged frog has contributed to the decline of 
this species (see Predation, Factor C, below). The recreational impact 
of anglers at high mountain lakes has been severe in the Sierra Nevada, 
with most regions reporting a level of use greater than that which the 
fragile lakeshore environments can withstand (Bahls 1992).
    Recreation may threaten all life stages of the mountain yellow-
legged frog through direct disturbance resulting from trampling by 
humans, packstock, or vehicles, including off-highway vehicles; 
harassment by pets; and associated habitat degradation (Cole and 
Landres 1996; USFS 2001). Studies have not been conducted to determine 
whether recreational activities are contributing to the decline of the 
mountain yellow-legged frog, and recreation has not been implicated as 
a cause of major decline of the mountain yellow-legged frog.

Dams and Water Diversions

    Dams and water diversions have altered aquatic habitats in the 
Sierra Nevada (Kondolf et al. 1996). Numerous reservoirs have been 
constructed within the range of the mountain yellow-legged frog. These 
include Huntington Lake, Florence Lake, Lake Thomas A. Edison, 
Saddlebag Lake, Convict Lake, Cherry Lake, and other reservoirs 
associated with Hetch Hetchy, Upper and Lower Blue Lakes, Lake Aloha, 
Silver Lake, Hell Hole Reservoir, French Meadow Reservoir, Lake 
Spaulding, and others. The extent of the impacts that these projects 
have had on the mountain yellow-legged frog is not known. The 
construction of dams probably has affected mountain yellow-legged frogs 
in the Sierra Nevada by altering their habitat and movements, and also 
by altering the distribution of predators (reservoirs are often stocked 
with non-native fish species that incidentally prey on mountain yellow-
legged frogs (See Predation, Factor C, below)). Mountain yellow-legged 
frogs cannot live in or move through the exposed shorelines created by 
reservoirs, nor can they successfully reproduce in these environments 
with predatory fishes unless there are shallow side channels or 
disjunct pools that are free of predatory fishes (Jennings 1996).
    Dams may alter the temperature and sediment load of the rivers they 
impound (Cole and Landres 1996). Dams, water diversions, and their 
associated structures can alter the natural flow regime with unseasonal 
and fluctuating releases of water, create habitat conditions unsuitable 
for native amphibians both upstream and downstream of dams, and act as 
barriers to movements by dispersing juvenile and migrating adult 
amphibians (Jennings 1996). Where dams act as barriers to mountain 
yellow-legged frog movement, they would effectively prevent genetic 
exchange between populations and the recolonization of sites. Water 
diversions that remove water from mountain yellow-legged frog habitat 
may adversely impact breeding success and adult survivorship if the 
diversion results in a lowering of the water level to the extent that 
the entire water column freezes in the winter, or to the extent that 
the habitat is rendered dry. These factors are likely to have 
contributed to the decline of mountain yellow-legged frogs and probably 
continue to pose a risk to the species.

Roads and Timber Harvest

    Any activity that severely alters the terrestrial environment, 
including road construction and timber harvest, is likely to result in 
the reduction and extirpation of amphibian populations in the Sierra 
Nevada (Jennings 1996). Most of the mountain yellow-legged frog 
populations are in areas such as national parks or designated 
wilderness areas where timber is not harvested (Bradford et al. 1994a; 
Drost and Fellers 1996; Knapp and Matthews 2000). Some of these 
populations, and others outside of these areas, are located at too high 
an altitude for timber to be harvested, so this activity is not 
expected to affect the majority of extant mountain yellow-legged frog 
populations. There are some mountain yellow-legged frog populations in 
areas where timber harvests have occurred in the past and others where 
it may occur in the future. There are also roads within the range of 
the mountain yellow-legged frog; however, neither of these factors has 
been implicated as an important contributor to the decline of this 
species (Jennings 1996).

Fire Management Activities

    Mountain yellow-legged frogs are generally found at high elevations 
in wilderness areas and national parks where vegetation is sparse and 
fire suppression activities are implemented infrequently. Potential 
impacts to the species resulting from fire management activities 
include: Water drafting (taking of water) from occupied ponds and 
lakes, resulting in direct mortality or rendering the habitat 
unsuitable for reproduction and survivorship; construction of fuel 
breaks either by hand or heavy equipment, potentially resulting in 
erosion and siltation of habitat; fire suppression with water 
applications or fire retardants; and

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increased human activity in the area, potentially disrupting mountain 
yellow-legged frog behavior.
    Fire retardant chemicals contain nitrogen compounds and/or 
surfactants (a subset of chemical additives usually used to facilitate 
application). Laboratory tests of these chemicals have shown that they 
can cause mortality in fishes and aquatic invertebrates by releasing 
surfactants and ammonia when they are added to water (Hamilton et al. 
1996), and similar effects are likely on amphibians. Therefore, if fire 
retardant chemicals were dropped in or near mountain yellow-legged frog 
habitat, they could have negative effects on individuals.
    In some areas within the range of the mountain yellow-legged frog, 
long-term fire suppression has changed forest structure and conditions 
where fire severity and intensity are higher (McKelvey et al. 1996). 
Prescribed fire has been used by land managers to achieve various 
silvicultural objectives, including the reduction of fuel loads. In 
some systems, fire is thought to be important in maintaining open 
aquatic and riparian habitats for amphibians (Russel et al. 1999). But 
severe and intense wild fires may reduce the ability of amphibians to 
survive such a fire. However, amphibians display adaptive behavior that 
may minimize mortality from fire, by taking cover in wet habitats or 
taking shelter in subterranean burrows, though the moist and permeable 
skin of amphibians increases their susceptibility to heat and 
dessication (Russel et al. 1999). Neither the direct nor indirect 
effects of prescribed fire or wildfire on the mountain yellow-legged 
frog have been studied, but because the species generally occupies high 
elevation habitat, fire is not a likely risk to this species in much of 
its range.
    In summary, historic grazing activities likely modified the habitat 
of the mountain yellow-legged frog throughout its range. Although 
grazing pressure has been significantly reduced from historic levels, 
grazing may continue to contribute to localized degradation and loss of 
suitable habitat, negatively affecting mountain yellow-legged frog 
populations. The effects of recreation, dams, water diversions, roads, 
timber harvests, and fire management activities on the mountain yellow-
legged frog are not well studied, and though they may have negatively 
affected mountain yellow-legged frogs and their habitat, they have not 
been implicated as primary factors in the decline of this species 
(Bradford et al. 1993; Bradford et al. 1994a; Jennings 1996; Knapp and 
Matthews 2000). However, recreation, dams, water diversions, roads, 
timber harvests, and fire management activities may be factors of 
secondary importance in the decline of the mountain yellow-legged frog 
and the modification of its habitat (Jennings 1996).
    B. Overutilization for commercial, recreational, scientific, or 
educational purposes. There is no known commercial market for mountain 
yellow-legged frogs, nor are there documented recreational or 
educational use for mountain yellow-legged frogs, although it is likely 
that they have been handled by curious members of the public, used as 
bait by anglers, and collected as pets. The mountain yellow-legged frog 
does not appear to be particularly popular among amphibian and reptile 
collectors; however, Federal listing could raise the value of the 
animals within wildlife trade markets and increase the threat of 
unauthorized collection above current levels (K. McCloud, Service, 
pers. comm. 2002). Even limited interest in the species could pose a 
serious threat to this animal.
    Scientific research may cause stress to mountain yellow-legged 
frogs through disturbance, including disruption of the species' 
behavior, handling individuals, and injuries associated with marking 
and tracking individuals. Scientific research has also resulted in the 
death of numerous individuals through the collection of museum 
specimens (Zweifel 1955; Jennings and Hays 1994). However, this is a 
relatively minor threat. Of greater concern are researchers 
contributing to the spread of pathogens via clothing and sampling 
equipment as they move between water bodies and populations (Bradford 
1991; Bradford et al. 1994a; Fellers et al. 2001). Given the 
uncertainty surrounding the potential for researchers to contribute to 
the spread of pathogens, researchers have begun to implement equipment 
sterilization procedures between survey sites (H. Eddinger, in litt. 
2002; R. Knapp, in litt. 2002; V. Vredenburg, in litt. 2002). For 
further discussion concerning the threat of disease, see Factor C 
    C. Disease or predation.


    Native predators of mountain yellow-legged frogs include the 
mountain garter snake (Thamnophis elegans elegans), valley garter snake 
(T. sirtalis fitchi), Brewer's blackbird (Euphagus cyanocephalus), 
Clark's nutcrackers (Nucifraga columbiana), coyotes (Canis latrans), 
and black bear (Ursus americanus) (Camp 1917; Grinnell and Storer 1924; 
Mullally and Cunningham 1956; Bradford 1991; Jennings et al. 1992; 
Feldman and Wilkinson 2000; V. Vredenburg et al. (in press)).
    Predation by introduced trout is the best-documented cause of the 
decline of the Sierra Nevada mountain yellow-legged frog, because it 
has been repeatedly observed that non-native fishes and mountain 
yellow-legged frogs rarely co-exist (Grinnell and Storer 1924; Needham 
and Vestal 1938; Mullally and Cunningham 1956; Cory 1962a, 1963; 
Bradford 1989; Bradford and Gordon 1992; Bradford et al. 1993, 1994a, 
1998; Drost and Fellers 1996; Jennings 1996; Knapp 1996; Knapp and 
Matthews 2000; Knapp et al. 2001; V. Vredenburg et al., (in press); 
USFS undated). The body of scientific research on the distributions of 
introduced trout and mountain yellow-legged frogs over time has 
conclusively demonstrated that introduced trout have negatively 
impacted mountain yellow-legged frogs over much of the Sierra Nevada 
(Bradford 1989; Bradford et al. 1993, 1994a, 1998; Knapp 1994, 1996; 
Drost and Fellers 1996; Knapp and Matthews 2000; Knapp et al. 2001). 
Mountain yellow-legged frogs and trout (native and non-native) do co-
occur at some sites, but these co-occurrences probably are mountain 
yellow-legged frog populations that would have negative population 
growth rates in the absence of immigration (Bradford et al. 1998; Knapp 
and Matthews 2000). Non-native fish stocking programs have been 
recognized to have negative ecological implications because non-native 
fish eat native aquatic flora and fauna, including amphibians and 
invertebrates (Bahls 1992; Erman 1996; Matthews et al. 2001; Pilliod 
and Peterson 2001; Schindler et al. 2001; Moyle 2002).
    Prior to extensive trout planting programs in the late 19th Century 
through the present, most streams and lakes in the Sierra Nevada at 
elevations above 1,800 m (6,000 ft) were without fishes. The 
distributions of several native fish species occur in lower-elevation 
aquatic habitats around the Sierra Nevada (Knapp 1996; Moyle et al. 
1996; Moyle 2002). The only major exception to the 1,800 m (6,000 ft) 
elevational limit for fishes within the range of the mountain yellow-
legged frog in the Sierra Nevada was the upper reaches of the Kern 
River where native fish such as the Little Kern golden trout 
(Oncorhynchus mykiss whitei) evolved (Moyle 2002). Natural barriers 
prevented fish from colonizing the higher elevation headwaters of the 
Sierra Nevada watershed (Moyle et al. 1996).
    With the Gold Rush and its associated increase in human habitation, 
habitat alteration, fish distribution and species

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composition began to change dramatically in high elevation lakes and 
streams (Moyle et al. 1996). Some of the first practitioners of trout 
stocking in the Sierra Nevada were the Sierra Club, local sportsmen's 
clubs, private citizens, and the U.S. military (Knapp 1996; Pister 
2001). As more hatcheries were built and distribution of non-native 
fish became better organized under State agency leadership, trout 
continued to be planted for the purpose of increased angler 
opportunities and success (Pister 2001). After World War II, the method 
of transporting trout to be stocked in high elevation areas changed 
from packstock to aircraft, which allowed stocking in more remote lakes 
and in greater numbers. It was at this point that CDFG began managing 
the bulk of the program, as it does today (Knapp 1996; Pister 2001).
    Brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), 
rainbow trout (Oncorhynchus mykiss), and other trout species 
assemblages have been planted in most streams and lakes of the Sierra 
Nevada (Knapp 1996; Moyle 2002). National forests in the Sierra Nevada 
have a higher proportion of lakes with non-native fish occupancy than 
do national parks (Knapp 1996). This is primarily because the NPS 
adopted a policy that greatly reduced fish stocking within their 
jurisdictional boundaries in the late 1970s. Fish stocking was 
terminated altogether in Sierra Nevada national parks in 1991 (Bahls 
1992; Knapp 1996).
    Knapp's (1996) review of previous trout distribution estimates and 
other available data on trout distribution in the Sierra Nevada 
indicated that approximately 63 percent of lakes larger than 1 ha (2.5 
ac) contain one or more non-native trout species, and as many as 85 
percent of lakes larger than 1 ha (2.5 ac) within national forests 
currently contain fish. Lakes larger than 1 ha (2.5 ac) within Sierra 
Nevada national parks were estimated to have from 35 to 50 percent non-
native fish occupancy, a 29 to 44 percent decrease since fish stocking 
was terminated (Knapp 1996). Though data on fish occupancy in streams 
is lacking throughout the Sierra Nevada, Knapp (1996) estimated 60 
percent of the streams in Yosemite National Park were occupied by 
trout, despite the curtailment of stocking practices over 25 years ago. 
Grinnell and Storer (1924) observed that fish stocking in Yosemite 
National Park ``nearly or quite eliminates the (mountain yellow-legged) 
    The most spatially comprehensive study of introduced fish and 
mountain yellow-legged frog distributions included an analysis of large 
landscapes affected by different fish stocking regimes, watersheds with 
differing trout distributions, and individual water bodies with varying 
fauna assemblages (Knapp and Matthews 2000). The Knapp and Matthews 
(2000) study on the effects of introduced fishes on the mountain 
yellow-legged frog in the Sierra and Inyo National Forests' John Muir 
Wilderness indicated 65 percent of water bodies 1 ha (2.5 ac) or larger 
were stocked with fishes on a regular basis up through the time of the 
study. Over 90 percent of the total water body surface area in the John 
Muir Wilderness in the Sierra and Inyo National Forests is occupied by 
non-native trout (Knapp and Matthews 2000). All fish stocking was 
terminated in 1977 in the adjacent Kings Canyon National Park. Knapp 
and Matthews (2000) surveyed all lakes and ponds, more than 1,700 water 
bodies, for fishes and mountain yellow-legged frogs. They concluded 
that a strong negative correlation exists between introduced trout and 
mountain yellow-legged frogs across the landscape, the watersheds, the 
individual water bodies of the study area, and possibly throughout the 
Sierra Nevada (Knapp and Matthews 2000). Consistent with this finding 
are the results of an analysis of the distribution of mountain yellow-
legged frog larvae that indicates that the presence and abundance of 
larvae are reduced dramatically in lakes that have fish as compared 
with lakes that were never stocked with fish (Knapp et al. 2001).
    Several aspects of the mountain yellow-legged frog's life history 
may exacerbate its vulnerability to predation and extirpation by non-
native trout (Bradford 1989; Bradford et al. 1993; Knapp 1996; Knapp 
and Matthews 2000). Mountain yellow-legged frogs are aquatic and are 
found mainly in lakes. This increases the probability that they will 
encounter non-native fishes whose distribution has been greatly 
expanded throughout the Sierra Nevada as a result of fish stocking. The 
multiple-year larval stage of the mountain yellow-legged frog 
necessitaties their use of permanent water bodies that are deep enough 
so as not to freeze, and so that overwintering adults can avoid oxygen 
depletion when the water is covered by ice (Mullally and Cunningham 
1956; Bradford 1983; Knapp and Matthews 2000). This further restricts 
larvae to water bodies suitable for and frequently inhabited by fishes 
(Knapp 1996) and isolates mountain yellow-legged frogs to fishless 
marginal habitats (Bradford et al. 1993; Knapp and Matthews 2000).
    Mountain yellow-legged frog populations have also been extirpated 
at some fishless bodies of water (Bradford 1991; Drost and Fellers 
1996). An explanation suggested for recent mountain yellow-legged frog 
population declines from fishless waters in the Sierra Nevada is the 
isolation and fragmentation of remaining populations by introduced 
fishes in the streams, which once provided the mountain yellow-legged 
frog with dispersal and recolonization routes (Bradford 1991; Bradford 
et al. 1993). Based on a survey of 95 basins within Sequoia and Kings 
Canyon National Parks, Bradford et al. (1993) calculated that the 
introduction of fishes into the study area resulted in approximately a 
ten-fold decrease in hydrologic connectivity between populations of 
mountain yellow-legged frogs. Knapp and Matthews (2000) believe that 
this has generally restricted mountain yellow-legged frogs to extremely 
isolated and marginal habitat. Trout influenced the isolation and 
fragmentation of mountain yellow-legged frog populations and 
metapopulations, making them more vulnerable to extirpation from random 
events (such as disease) than large, unfragmented metapopulations 
(Wilcox 1980; Hanski and Simberloff 1997; Bradford et al. 1993; Knapp 
and Matthews 2000). Given the metapopulation structure of the mountain 
yellow-legged frog, these isolated population locations may have higher 
extinction rates than colonization rates because trout prevent 
successful recolonization and dispersal to and from these sites 
(Bradford et al. 1993; Blaustein et al. 1994a; Knapp and Matthews 
2000). In addition, amphibians may not recolonize unoccupied sites 
following local extinctions because of physiological constraints; the 
tendency for amphibians, including the mountain yellow-legged frog, to 
move only short distances; and high site fidelity (Blaustein et al. 
    Knapp and Matthews (2000) suggest that the predation of mountain 
yellow-legged frogs by fishes as observed by Grinnell and Storer 
(1924), and the documented declines of the 1970s (Bradford 1991; 
Bradford et al. 1994a; Stebbins and Cohen 1995), are not the start of 
the mountain yellow-legged frog's decline, but rather the end of a long 
decline that started soon after fish introductions to the Sierra Nevada 
began in the mid-1800s. Knapp and Matthews (2000) note that 
metapopulation theory (Hanski 1997) predicts this type of time lag from 
habitat modification to population extinction.
    Fish-induced declines of the mountain yellow-legged frog may be 
reversed in some locations with an

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intensive and focused effort to restore fishless conditions (Knapp and 
Matthews 1998, 2000; Knapp et al. 2001). Removing fish from lakes with 
an adjacent source population of mountain yellow-legged frogs can 
result in the rapid recolonization of the lake by the species and, over 
time, may result in recovery to conditions similar to lakes that had 
never been stocked (Knapp et al. 2001; Briggs et al. 2002; R. Knapp, in 
litt. 2002). Trout removal from several lakes has been successfully 
accomplished in the Sierra National Forest's John Muir Wilderness. This 
has resulted in the natural recolonization and initial recovery of 
mountain yellow-legged frogs in one of the lakes where trout were 
removed (R. Knapp, in litt. 2002). In the other two lakes within this 
basin where trout were removed, mountain yellow-legged frogs were 
successfully reintroduced, and there is evidence of reproduction in 
these translocated populations (R. Knapp, in litt. 2002). Sequoia and 
Kings Canyon National Parks have initiated a mountain yellow-legged 
frog restoration project which employs gill nets and electrofishing to 
remove fish from select lakes and adjacent stream segments at sites 
with little to no human visitation (NPS 2001). However, because of the 
cumulative effect of past mountain yellow-legged frog population 
declines (upwards of 80 percent in the 20th century), and ongoing 
population declines caused by disease or other factors, the 
recolonization of lakes restored to fishless conditions will grow less 
likely as the number of viable source populations of mountain yellow-
legged frogs dwindles (Knapp et al. 2001).
    The best-documented cause of the decline of the mountain yellow-
legged frog is the introduction of non-native fish (Bradford 1989; 
Bradford et al. 1993; Knapp and Matthews 2000). In summarizing the 
effects of non-native fish on the mountain yellow-legged frog, it is 
important to recognize that: (1) The vast majority of the range of the 
mountain yellow-legged frog did not evolve with any species of fish as 
this frog predominantly occurs in water bodies above natural fish 
barriers; (2) water bodies throughout the range of the mountain yellow-
legged frog have been intensively stocked with non-native fish, and 
where stocking has terminated, self-sustaining fish populations 
continue to persist; (3) the multiple year larval stage of the mountain 
yellow-legged frog prevents successful recruitment to populations that 
co-occur with non-native fish because when water bodies ice over in 
winter, larvae are forced from shallow margins of lakes and ponds into 
deeper unfrozen water where they are vulnerable to predation by non-
native fish; (4) adult mountain yellow-legged frogs that co-occur with 
non-native fish are vulnerable to predation when they are exposed to 
these fish, such as when adult mountain-yellow legged frogs overwinter 
at the bottom of deep water bodies; and (5) the introduction of non-
native fish has fragmented mountain yellow-legged frog habitat, 
isolated populations from each other, and generally restricted 
remaining mountain yellow-legged frog populations to marginal habitats, 
thereby increasing the likelihood of localized extinctions without the 
possibility of recolonization.


    There have been recent reports from around the globe of disease- 
and pathogen-related population declines and mass die offs of 
amphibians (Bradford 1991; Blaustein et al. 1994b; Alford and Richards 
1999). Mountain yellow-legged frogs are susceptible to diseases such as 
red-leg disease, caused by the bacterial pathogen Aeromonas hydrophila. 
This pathogen can cause localized population crashes (Bradford 1991). 
Bradford (1991) suggested that one such outbreak was a result of 
overcrowding within the mountain yellow-legged frog population. Though 
it is opportunistic and successfully attacks the immunosuppressed 
individuals, this pathogen appears to be highly contagious, affecting 
the epidermis and digestive tract of otherwise healthy amphibians 
(Shotts 1984; Carey 1993; Carey and Bryant 1995). Grinnell and Storer 
(1924) reported red-legged disease had infected some mountain yellow-
legged frog populations in Yosemite National Park.
    In California, chytridiomycosis (Batrachochytrium dendrobatidis), 
more commonly known as chytrid fungus, has been detected in nine 
amphibian species, including the mountain yellow-legged frog (Fellers 
and Green, pers. comm., as cited in Briggs et al. 2002; R. Knapp, 
Sierra Nevada Aquatic Research Laboratory, University of California at 
Santa Barbara, pers. comm. 2002). Fellers et al. (2001) report the 
presence of several bacteria and chytrid fungus in larval and recently 
metamorphosed mountain yellow-legged frogs from sites within the Sierra 
Nevada. Chytrid fungus affects the keratinized (horny epidermal tissue) 
mouth parts and epidermal tissue of larvae and metamorphosed mountain 
yellow-legged frogs (Fellers et al. 2001). Though little is known about 
its life history in the Sierra Nevada, chytrid fungus has a simple 
asexual life cycle, and chytrids can generally withstand adverse 
conditions such as freezing or drought (Briggs et al. 2002). A research 
effort is underway to study the dynamics of this pathogen and the 
mountain yellow-legged frog within the Sierra Nevada (Briggs et al. 
2002). Whether adult frogs acquire this fungus from tadpoles or whether 
the fungus is retained through metamorphosis is unknown. However, the 
mountain yellow-legged frog may be especially vulnerable to infections 
of chytrid fungus as all life stages of the mountain yellow-legged frog 
share the same habitat nearly year round, facilitating the transmission 
of this fungus to individuals at different life stages within a 
population (Fellers et al. 2001). Survey results from 2000 in Yosemite 
and Sequoia-Kings Canyon National Parks indicate 24 percent of the 
mountain yellow-legged frog populations show signs of chytrid infection 
(Briggs et al. 2002). In mountain yellow-legged frogs, chytrid fungus 
has been observed to result in overwinter mortality and mortality 
during metamorphosis (Briggs et al. 2002). Effects of chytrid fungus on 
host populations of the mountain yellow-legged frog are variable, 
ranging from extinction, persistence with a high level of infection, to 
persistence with low levels of infection (Briggs et al. 2002). Studies 
of the microscopic structure of tissue and other evidence suggests 
chytrid fungus caused many of the recent extinctions in the Sierra 
National Forest's John Muir Wilderness Area and in Kings Canyon 
National Park, where 41 percent of the populations went extinct between 
1995 and 2002 (R. Knapp, in litt. 2002).
    Chytrid fungus affecting wild frog populations was not documented 
until the late 1990s. Since then, it has been reported in amphibian 
populations worldwide (Fellers et al. 2001). We do not know how long 
the mountain yellow-legged frog populations have been exposed to 
chytrid fungus. Red-leg disease is typically a secondary infection 
following a chytrid infection. If this was also the case in the early 
1900s, then it would suggest that what Grinnell and Storer (1924) 
actually were seeing was chytrid infections (R. Knapp, in litt. 2002). 
During a visual examination of mountain yellow-legged frog tadpoles 
preserved between 1993 and 1999, abnormalities attributed to the 
chytrid fungus were detected on 14 of 36 specimens and no abnormalities 
were detected on any of the 43 tadpole specimens collected between 1955 
and 1976 (Fellers et al. 2001). This indicates

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that chytrid fungus infections may be a recent pathogen to affect the 
mountain yellow-legged frog, although visual detections of chytrid-like 
abnormalities may be neither longlasting nor attributable to this 
fungus (Fellers et al. 2001; V. Vredenburg, in litt. 2002). Since at 
least 1976, chytrid fungus has affected adult Yosemite toads (Green and 
Kagarise Sherman 2001). The Yosemite toad is sympatric with the 
mountain yellow-legged frog (their ranges overlap). Therefore, it is 
possible that this pathogen has affected both of these amphibian 
species since at least the mid-1970s. Chytrid fungus is only a recently 
detected pathogen in amphibian populations; this may be an emerging 
infectious disease. How it has been transmitted to the mountain yellow-
legged frog is unclear (Briggs et al. 2002).
    Saprolegnia is a globally distributed fungus that commonly attacks 
all life stages of fishes (especially hatchery reared fishes), and has 
recently been documented to attack and kill egg masses of western toads 
(Bufo boreas) (Blaustein et al. 1994b). This pathogen may be introduced 
through fish stocking or it may already be established in the aquatic 
ecosystem. Fishes and/or migrating or dispersing amphibians may be a 
vector for this fungus (Blaustein et al. 1994b; Kiesecker et al. 2001). 
Saprolegnia has not been reported in the mountain yellow-legged frog; 
however, if hatchery fishes are vectors of this disease, it may have 
been introduced via fish stocking into historically occupied mountain 
yellow-legged frog habitat.
    No viruses were detected in the specimens of mountain yellow-legged 
frogs that Fellers et al. (2001) analyzed for chytrid fungus. In Kings 
Canyon National Park, Knapp (pers. comm. 2002) found mountain yellow-
legged frogs showing symptoms preliminarily attributed to a ranavirus. 
Mechanisms for disease transmission, including viruses, to the mountain 
yellow-legged frog remain unknown. However, Mao et al. (1999) isolated 
identical iridoviruses from wild co-occurring populations of the 
threespine stickleback (Gasterostelus aculeatus) and the red-legged 
frog (Rana aurora), indicating that infection by a given virus is not 
limited to a single species, and that iridoviruses can infect animals 
belonging to different taxonomic classes. This suggests that if virus-
hosting trout are introduced into mountain yellow-legged frog habitat, 
they may be a vector of amphibian viruses.
    Whether amphibian pathogens in the high Sierra Nevada have always 
coexisted with amphibian populations or if their presence is a recent 
phenomenon is uncertain (Fellers et al. 2001). The susceptibility of 
amphibians to pathogens may have recently increased in response to 
anthropogenic (human-caused) environmental disruption (Carey 1993; 
Blaustein et al. 1994b; Carey et al. 1999). This hypothesis suggests 
that environmental changes may be indirectly responsible for certain 
amphibian dieoffs by immune system suppression of larval or 
postmetamorphic amphibians to the extent that they are not resistant to 
diseases (Carey 1993; Blaustein et al. 1994b; Carey et al. 1999). 
Pathogens such as red-leg disease, which are present in fresh water and 
in healthy organisms, may erupt, potentially causing localized 
amphibian population dieoffs when the immune system of individuals 
within the host population are suppressed (Carey 1993; Carey and Bryant 
1995). Wind-borne pesticides from upwind agriculture potentially 
contribute to contaminant concentrations that may be high enough to 
compromise amphibian immune systems (Carey 1993; Carey et al. 1999; 
Daszak et al. 1999). Recreationists may contribute to the spread of 
pathogens between water bodies and populations via clothing and fishing 
equipment. Given the uncertainty surrounding the potential for 
researchers to contribute to the spread of pathogens, they have begun 
to implement equipment sterilization procedures between survey sites 
(H. Eddinger, in litt. 2002; R. Knapp, in litt. 2002; V. Vredenburg, in 
litt. 2002).
    A compounding effect of disease-caused extinctions of mountain 
yellow-legged frogs is that recolonization may never occur, because 
streams connecting extirpated sites to extant populations now contain 
introduced fishes, which act as barriers to frog movement within 
metapopulations. This isolates the remaining populations of mountain 
yellow-legged frogs from each other (Bradford 1991; Bradford et al. 
    In summary, mountain yellow-legged frogs are vulnerable to multiple 
pathogens, whose effects range from population persistence, with low 
levels of infection within populations, to extinction of entire 
populations. Little is understood about these pathogens, making disease 
difficult to manage without a better understanding of their life 
histories and modes of transmission. Red-leg disease and chytrid fungus 
have been identified as having potentially catastrophic effects 
(localized extinction) on mountain yellow-legged frog populations. 
Though chytrid fungus was only recently discovered to affect amphibians 
(including the mountain yellow-legged frog), chytrid currently appears 
to have the highest rate of infection relative to other pathogens in 
mountain yellow-legged frog populations. The negative consequences of 
chytrid infection to mountain yellow-legged frog populations may be 
exacerbated by the fragmentation and isolation of remaining mountain 
yellow-legged frog metapopulations and populations due to non-native 
fish introductions. This is because there may not be an adjacent 
mountain yellow-legged frog population with habitat connectivity that 
is able to recolonize an area following a pathogen-caused extinction 
    D. The inadequacy of existing regulatory mechanisms. Existing 
regulatory mechanisms that could provide some protection for the 
mountain yellow-legged frog in the Sierra Nevada include: (1) Federal 
laws and regulations; (2) State laws and regulations; and (3) local 
land use processes and ordinances. However, these regulatory mechanisms 
have not prevented non-native fish introductions, pathogen outbreaks, 
and habitat modifications, all of which result in population declines 
of mountain yellow-legged frogs in the Sierra Nevada.


    In response to the overgrazing by livestock of the available 
rangelands from the 1800s to the 1930s and the subsequent years of the 
Dust Bowl, Congress passed the Taylor Grazing Act in 1934. This was an 
effort to stop the damage to the remaining public lands from 
overgrazing and soil depletion, to provide for an order to grazing on 
public lands, and to attempt to stabilize the livestock industry using 
these lands (Meehan and Platts 1978; Public Lands Council et al. v. 
Babbitt Secretary of the Interior et al. (167 F. 3d 1287)). Although 
passage of the Taylor Grazing Act resulted in reduced grazing in some 
areas, it did not reduce grazing severity, as use remained high, and it 
did not allow regeneration of many meadow areas (Beesley 1996; Menke et 
al. 1996; Public Lands Council et al. v. Babbitt Secretary of the 
Interior et al. (167 F. 3d 1287)). The Taylor Grazing Act of 1934, as 
amended, did initiate some grazing reform, possibly lessening impacts 
of livestock grazing on many species and populations of wild plants and 
animals, including the mountain yellow-legged frog and its habitat. 
However, it does not have any provisions specific to the protection of 
either the mountain yellow-legged frog or its habitat.
    The Multiple-Use Sustained-Yield Act of 1960 (MUSY), as amended, 

[[Page 2297]]

direction that the national forests be managed using principles of 
multiple use and to produce a sustained yield of products and services. 
Specifically, MUSY gives policy that the national forests are 
established and shall be administered for outdoor recreation, range, 
timber, watershed, wildlife, and fish purposes. Land management for 
multiple uses has inherent conflicts. However, MUSY directs resource 
management not to impair the productivity of the land while giving 
consideration to the relative values of the various resources, though 
not necessarily in terms of the greatest financial return or unit 
output. This act provides direction to the USFS that wildlife (which 
includes the mountain yellow-legged frog), is a value that must be 
managed for, though discretion is given to each national forest when 
considering the value of the mountain yellow-legged frog relative to 
the other uses for which they must manage. MUSY does not have any 
provisions specific to the protection of either the mountain yellow-
legged frog or its habitat.
    The Federal Land Policy and Management Act of 1976 (FLPMA), as 
amended, gives management direction to the Bureau of Land Management; 
however, its application is to all Federal lands, including those 
managed by the USFS. FLPMA includes a provision requiring that 50 
percent or $10,000,000 per year, whichever is greater, of all moneys 
received through grazing fees collected on Federal lands (including the 
USFS-administered lands within the range of the mountain yellow-legged 
frog) be spent for the purpose of on-the-ground range rehabilitation, 
protection, and improvement. This includes all forms of rangeland 
betterment such as fence construction, water development, and fish and 
wildlife enhancement. Half of the appropriated amount must be spent 
within the national forest where such moneys were derived. FLPMA 
provides for some rangeland improvements intended for the long-term 
betterment of forage conditions and resulting benefits to wildlife, 
watershed protection, and livestock production. Land improvements 
initiated pursuant to FLPMA may have benefitted the mountain yellow-
legged frog and its habitat; however, some mountain yellow-legged frog 
habitat has continued to be destabilized and deteriorate due to 
livestock grazing on lands subject to FLPMA (R. Knapp, in litt. 1993a, 
1993b, 1994, 2002; Jennings 1995, 1996). We are unaware of any USFS-
initiated projects developed under FLPMA for the specific benefit of 
the mountain yellow-legged frog, and, if the USFS has conducted such 
projects, what effects they have had.
    The Wilderness Act of 1964 established a National Wilderness 
Preservation System made up of federally owned areas designated by 
Congress as ``wilderness'' for the purpose of preserving and protecting 
designated areas in their natural condition. Commercial enterprise, 
road construction, use of motorized vehicles or other equipment, and 
structural developments are generally prohibited within designated 
wilderness. Livestock grazing is permitted within designated 
wilderness, subject to other applicable laws, if it was established 
prior to the passage of this act. The Wilderness Act does not 
specifically mention fish stocking although it does state that it shall 
not affect the jurisdiction or responsibilities of States with wildlife 
and fish responsibilities in the national forests. Whether fish 
stocking is permitted under the Wilderness Act is an issue that has 
been debated (Bahls 1992; Landres et al. 2001). However, it generally 
has not limited fish stocking in the Sierra Nevada (Knapp 1996). 
Passage of the Wilderness Act has not positively affected mountain 
yellow-legged frog populations in wilderness areas of the Sierra Nevada 
as it does not prevent fish stocking (Knapp and Matthews 2000). 
Potentially, the Wilderness Act has helped to protect mountain yellow-
legged frog habitat from development or other types of habitat 
conversions and disturbances; however, mountain yellow-legged frog 
populations have continued to decline despite its passage.
    The National Environmental Policy Act of 1969 (NEPA), as amended, 
requires all Federal agencies to formally document and publicly 
disclose the environmental impacts of all actions and management 
decisions. NEPA documentation is provided in either an environmental 
impact statement, an environmental assessment, or a categorical 
exclusion, and may be subject to administrative appeal or litigation. 
The Pacific Southwest Region (Region 5) of the USFS considers the 
mountain yellow-legged frog a Forest Service sensitive species. 
Therefore, as part of USFS policy, the analysis related to planning 
under the National Forest Management Act of 1976 (NFMA) and conducted 
by the USFS to evaluate potential management decisions under NEPA 
includes a biological evaluation which discloses potential impacts to 
sensitive species at both the forest planning level and on a project-
by-project basis. Under USFS policy (FSM 2620 and 2670), projects must 
not result in contributing to a trend towards Federal listing of 
species. Despite the analyses pursuant to NEPA on all Federal actions 
potentially affecting the mountain yellow-legged frog in the Sierra 
Nevada, and analyses pursuant to both NFMA and NEPA on national 
forests, the species' populations have continued to decline (Bradford 
et al. 1993, 1994a; Drost and Fellers 1996; Jennings 1996; Knapp 1996).
    The revised NMFA planning regulations recently proposed by the USFS 
(67 FR 72770) may affect the status of this policy requirement (FSM 
2620 and 2670), as the underlying regulatory framework pertaining to 
providing for the diversity of plant and animal communities is proposed 
to be substantially altered from the existing regulatory requirement. 
The outcome of both the regulations and the related policies that tier 
to them is uncertain.
    In the few cases where the Sierra Nevada mountain yellow-legged 
frog occurs in habitat occupied by species listed pursuant to the Act, 
the mountain yellow-legged frog may be afforded protection under this 
legislation. The native Lahontan cutthroat trout (Oncorhynchus clarki 
henshawi) and native Paiute cutthroat trout (Oncorhynchus clarki 
seleneris) are federally listed species, occurring predominantly in 
drainages on the east side of the Sierra Nevada. They co-occur with 
several small populations of mountain yellow-legged frogs at lower 
elevations on the edge of the species' range. The native Little Kern 
golden trout is a federally threatened species, co-occurring with the 
mountain yellow-legged frog in a few isolated locations in the southern 
Sierra Nevada (Knapp 1996; Moyle 2002). Recovery actions for these 
trout species, such as physical habitat protection, may benefit the 
mountain yellow-legged frog. For example, on the Tahoe National Forest, 
grazing, recreation, and other restrictions for the benefit of the 
Lahontan cutthroat trout and its habitat have been established. One of 
these measures that benefits the mountain yellow-legged frog is the 
establishment of a bank protection measure that allows for 10 percent 
bank disturbance (measured as bare ground accompanied by soil 
displacement and/or cutting of plant root crowns). Elsewhere the 
standard for bank disturbance is 20 percent (A. Carlson, in litt. 
2002). However, the use of chemicals or electrofishing to remove non-
native fish from threatened trout habitat may adversely affect mountain 
yellow-legged frogs present at the time of treatment. Additionally, 
listed native trout species

[[Page 2298]]

may prey on the mountain yellow-legged frog at sites where they co-
    The Forest and Rangeland Renewable Resources Planning Act of 1974, 
as amended by NFMA, specifies that all national forests must have a 
land and resource management plan (LRMP). The purpose of the LRMP is to 
guide and set standards for all natural resource management activities 
for the life of the plan (10 to 15 years) on each national forest. NFMA 
requires the USFS to incorporate standards and guidelines into LRMPs. 
This has historically been done through a NEPA process, including 
provisions to manage plant and animal communities for diversity, based 
on the suitability and capability of the specific land area in order to 
meet overall multiple-use objectives. The 1982 planning regulations for 
implementing NFMA, under which all existing forest plans were prepared 
and which still guide management, also required that fish and wildlife 
habitat on national forest system lands ``* * * shall be managed to 
maintain viable populations of existing native and desired non-native 
vertebrate species in the planning area. For planning purposes, a 
viable population is one which has the estimated numbers and 
distribution of reproductive individuals to insure its continued 
existence is well distributed in the planning area. In order to insure 
that viable population will be maintained, habitat must be provided to 
support, at least, a minimum number of reproductive individuals and 
that habitat must be well distributed so that those individuals can 
interact with others in the planning area.''
    In 2001, a record of decision (ROD) was signed by the USFS for the 
Sierra Nevada Forest Plan Amendment (SNFPA), based on the final 
environmental impact statement (FEIS) for the SNFPA effort and prepared 
under the 1982 NFMA planning regulations. The ROD amends the USFS 
Pacific Southwest Regional Guide, the Intermountain Regional Guide, and 
the LRMPs for national forests in the Sierra Nevada and Modoc Plateau. 
This document affects land management on all national forests 
throughout the range of the mountain yellow-legged frog. The SNFPA 
addresses and gives management direction on issues pertaining to old 
forest ecosystems; aquatic, riparian, and meadow ecosystems; fire and 
fuels; noxious weeds; and lower westside hardwood ecosystems of the 
Sierra Nevada.
    Relevant to the mountain yellow-legged frog, the ROD for the SNFPA 
aims to protect and restore aquatic, riparian, and meadow ecosystems, 
and to provide for the viability of its associated native species via 
an aquatic management strategy. The aquatic management strategy is a 
general framework with broad policy direction. Implementation of this 
strategy is intended to take place at the landscape and project levels. 
There are nine goals associated with the aquatic management strategy. 
They include: (1) The maintenance and restoration of water quality to 
comply with the Clean Water Act (CWA) and the Safe Drinking Water Act; 
(2) the maintenance and restoration of habitat to support viable 
populations of native and desired non-native riparian-dependent species 
and to reduce negative impacts of non-native species on native 
populations; (3) the maintenance and restoration of species diversity 
in riparian areas, wetlands, and meadows to provide desired habitats 
and ecological functions; (4) the maintenance and restoration of the 
distribution and function of biotic communities and biological 
diversity in special aquatic habitats (such as springs, seeps, vernal 
pools, fens, bogs, and marshes); (5) the maintenance and restoration of 
spatial and temporal connectivity for aquatic and riparian species 
within and between watersheds to provide physically, chemically, and 
biologically unobstructed movement for their survival, migration, and 
reproduction; (6) the maintenance and restoration of hydrologic 
connectivity between floodplains, channels, and water tables to 
distribute flood flows and to sustain diverse habitats; (7) the 
maintenance and restoration of watershed conditions as measured by 
favorable infiltration characteristics of soils and diverse vegetation 
cover to absorb and filter precipitation, and to sustain favorable 
conditions of stream flows; (8) the maintenance and restoration of 
instream flows sufficient to sustain desired conditions of riparian, 
aquatic, wetland, and meadow habitats and to keep sediment regimes 
within the natural range of variability; and (9) the maintenance and 
restoration of the physical structure and condition of stream banks and 
shorelines to minimize erosion and sustain desired habitat diversity. 
If these goals are pursued and met, the mountain yellow-legged frog and 
its habitat could benefit. These goals, though broadly stated, include 
measures to reduce impacts of non-native trout predation on mountain 
yellow-legged frogs as well as the resulting isolation of populations. 
These goals, if met, would also restore mountain yellow-legged frog 
aquatic habitats, including meadows, fens, stream banks, and shorelines 
that have been degraded by a history of livestock use.
    To help meet these goals, the aquatic management strategy proposes 
a broad initial action to address the mountain yellow-legged frog in a 
conservation plan developed by the USFS with other State and Federal 
agencies; an effort by the USFS to do this is underway. Where known 
locations of mountain yellow-legged frogs occur on the national 
forests, critical aquatic refuges will be designated. A primary 
management goal for the critical aquatic refuges is to contribute to 
the viability and recovery of sensitive species (including the mountain 
yellow-legged frog) through habitat preservation, enhancement, 
restoration, or connectivity. Within the aquatic management strategy, 
critical aquatic refuges are given highest priority for evaluating how 
existing and proposed activities are consistent with the goals of the 
strategy. The aquatic management strategy directs existing and proposed 
activities within critical aquatic refuges to be consistent with the 
goals of the critical aquatic refuges. This evaluation will be made 
using the riparian conservation objectives and associated standards and 
guidelines, as defined in the ROD for the SNFPA. One such standard and 
guideline specific to the mountain yellow-legged frog includes the 
avoidance of pesticide applications from within 152 m (500 ft) of sites 
known to be occupied by the species.
    Management standards and guidelines in the SNFPA ROD for the 
Yosemite toad will also benefit the mountain yellow-legged frog in 
areas where these two species overlap. These standards and guidelines 
exclude livestock from standing water and saturated soils in wet 
meadows and associated streams and springs occupied by Yosemite toads, 
or identified as essential habitat for this species in the USFS's 
conservation assessment for this species.
    The SNFPA includes requirements for monitoring to determine how 
well the aquatic management strategy goals and the riparian 
conservation objectives have been met, and how closely management 
standards and guidelines have been applied.
    Our review of the SNFPA FEIS and ROD indicate that full 
implementation of the SNFPA would benefit the mountain yellow-legged 
frog and its habitat. National forests affected by the SNFPA are 
responsible for implementing it; however, implementation is subject to 
funding. Also, current direction from within the USFS is to internally 
review the entire record (including the FEIS, the existing

[[Page 2299]]

ROD, public and agency comments, and the appeals and responsive 
statements), to evaluate primarily the effects of its implementation on 
grazing, recreation, and impacts to local communities (J. Blackwell, 
USFS, in litt. 2001). This review and assessment may result in proposed 
changes to the SNFPA and its associated documents. Therefore, the 
extent to which it will continue to be implemented, and the extent to 
which it may benefit the mountain yellow-legged frog and its habitat, 
remain undetermined. There is additional uncertainty because the 
proposed changes to the NFMA planning regulations recently issued by 
Forest Service (67 FR 72770) contain two options for meeting the NFMA 
direction to provide for the diversity of plant and animal communities, 
and both options would change the current regulation pertaining to 
forest planning to provide habitat to support viable populations.
    The statute establishing the National Park Service, commonly 
referred to as the National Park Service Organic Act (39 Stat. 535; 16 
U.S.C. 1,2,3 and 4) states that the NPS will administer areas under 
their jurisdiction ``. . .by such means and measures as conform to the 
fundamental purpose of said parks, monuments, and reservations, which 
purpose is to conserve the scenery and the natural and historic objects 
and the wildlife therein and to provide for the enjoyment of the same 
in such manner and by such means as will leave them unimpaired for the 
enjoyment of future generations.'' The 2001 edition of NPS Management 
Policies (NPS D1416) further elaborates on how impacts on park 
resources, including native organisms, will not be allowed to the level 
that they would constitute impairment: ``To comply with this mandate, 
park managers must determine in writing whether proposed activities in 
parks would impair natural resources. Park managers must also take 
action to ensure that ongoing NPS activities do not cause impairment. 
In cases of doubt as to the impact of activities on park natural 
resource, the Service will decide in favor of protecting the natural 
resources.'' Sequoia, Kings Canyon, and Yosemite National Parks began 
phasing out fish stocking in 1969 and terminated this practice entirely 
in 1991 (Bahls 1992; Knapp 1996).
    Under section 404 of the Clean Water Act, the U.S. Army Corps of 
Engineers (Corps) regulates the discharge of fill material into waters 
of the United States, including wetlands. Section 404 regulations 
require applicants to obtain a permit for projects that involve the 
discharge of fill material into waters of the United States, including 
wetlands. Projects that are subject to regulation may qualify for 
authorization to place fill material into headwaters and isolated 
waters, including wetlands, under several nationwide permits. The use 
of nationwide permits by an applicant or project proponent is normally 
authorized with minimal environmental review by the Corps. An 
individual permit may be required by the Corps if a project otherwise 
qualifying under a nationwide permit would have greater than minimal 
adverse environmental impacts. However, few projects that include fill 
of wetlands are likely to occur within the range of the mountain 
yellow-legged frog.


    The State of California considers the mountain yellow-legged frog a 
species of special concern, but it is not State listed as a threatened 
or endangered species and thus is not protected 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 with a sport fishing license. Possession or take of the 
mountain yellow-legged frog is authorized under special permit from the 
CDFG. This gives the frog some legal protection from collecting, but 
does not protect it from other causes of mortality or alterations to 
its habitat.
    The California Forest Practice rules set guidelines for the design 
of timber harvests on private land to reduce impacts on non-listed 
species. These rules have little application to the protection of the 
mountain yellow-legged frog because the vast majority of the species' 
range is on Federal land, and much of its range is too high in 
elevation to overlap with lands used for commercial timber harvest.
    The California Department of Pesticide Regulation (CDPR) has 
authority to restrict the use of pesticides. The CDPR Toxic Air 
Contaminant (TAC) Program includes assessment of the risks posed by 
airborne pesticides; this assessment involves collection of air samples 
near sites of pesticide application and in communities near those 
sites. If air samples indicate that reductions in exposure are needed, 
mitigation measures are developed to bring about those reductions (CDPR 
2001). However, the TAC program is intended primarily to protect human 
health, and air samples are not taken at far distant locations from 
application sites, like those inhabited by the mountain yellow-legged 
frog in the Sierra Nevada.
    The California Environmental Quality Act (CEQA) pertains to 
projects on non-Federal lands and requires review of any project that 
is undertaken, funded, or permitted by a State or local governmental 
agency. If a project with potential impacts on the mountain yellow-
legged frog in the Sierra Nevada is reviewed, CDFG personnel could 
determine that, although not state-listed, the frog is de facto an 
endangered, threatened, or rare species under section 15380 of CEQA. 
Once significant effects are identified, the lead agency has the option 
of requiring mitigation for effects through changes in the project or 
to decide that overriding considerations make mitigation infeasible 
(CEQA Sec. 21002). In the latter case, projects may be approved that 
cause significant environmental damage, such as destruction of state-
listed endangered species or their habitat. Protection of listed 
species through CEQA is, therefore, dependent on the discretion of the 
agency involved. In addition, fish stocking is not subject to 
disclosure of its potential environmental impacts because it is exempt 
from CEQA under Article 19 section 15301(j). Therefore, the effects of 
fish stocking on the mountain yellow-legged frog are not analyzed 
pursuant to CEQA. Also, the vast majority of the species' range is on 
Federal land and is affected by Federal actions (other than the State-
sponsored fish stocking) that are not subject to CEQA analysis.
    Section 1603(a) of the California Fish and Game Code requires a 
permit from the CDFG for any activity that may alter the bed, channel, 
or bank of any river, stream, or lake. The permit may incorporate 
measures to minimize adverse impacts to fish and wildlife. Therefore, 
this regulation may offer some protection of mountain yellow-legged 
frog habitat. The extent to which this regulation has provided the 
mountain yellow-legged frog with protection is unknown because much of 
the range of this species is on federal lands where few habitat 
modifications subject to this permit are proposed.
    The CDFG is practicing an informal policy on fish stocking in the 
range of the mountain yellow-legged frog in the Sierra Nevada. This 
policy directs that: (1) Fish will not be stocked in lakes with known 
populations of mountain yellow-legged frogs, nor in lakes which have 
not yet been surveyed for mountain yellow-legged frog presence; (2) 
waters will be stocked only with a fisheries management justification; 
and (3) the number of stocked lakes will be reduced over time. In 2001, 
the number of lakes stocked with fish within the range of the mountain 

[[Page 2300]]

frog in the Sierra Nevada was reduced by 75 percent (C. Milliron, in 
litt. 2002; E. Pert, CDFG, pers. comm. 2002; E. Pert et al., pers. 
comm. 2002). Water bodies within the same basin and 2 km (1.25 mi) from 
a known mountain yellow-legged frog population will not be stocked with 
fish unless stocking is justified through a management plan that 
considers all the aquatic resources in the basin, or unless there is 
heavy angler use and no opportunity to improve the mountain yellow-
legged frog habitat (C. Milliron, in litt. 2002). This policy has not 
been finalized in writing (E. Pert et al., pers. comm. 2002).
    The CDFG is in the process of developing management plans for 
basins within the range of the mountain yellow-legged frog in the 
Sierra Nevada (CDFG 2001; C. Milliron, in litt. 2002; E. Pert, pers. 
comm. 2002; E. Pert et al., pers. comm. 2002). For example, a plan has 
been developed, signed, and initiated for the Big Pine Creek wilderness 
basin in the Inyo National Forest's John Muir Wilderness (CDFG 2001), 
and a similar plan is proposed for the Gable Lakes basin, also in the 
John Muir Wilderness area of the Inyo National Forest (B. Miller, CDFG, 
in litt. 2001). The objectives of the Big Pine Creek wilderness basin 
plan specific to the mountain yellow-legged frog include management in 
a manner that maintains or restores native biodiversity and habitat 
quality, supports viable populations of native species, and provides 
for recreational opportunities that consider historic use patterns 
(CDFG 2001). Under this plan, some lakes are managed primarily for the 
mountain yellow-legged frog, with few or no angling opportunities, 
while lakes with high demand for recreational angling are managed 
primarily for that purpose (CDFG 2001). Preliminary results indicate 
that where the plans are being implemented, the management objective to 
restore mountain yellow-legged frog habitat is being achieved, and in 
some areas, mountain yellow-legged frog populations have responded 
positively (C. Milliron, pers. comm. 2002). We anticipate that the 
development and implementation of these basin management plans will be 
effective in reversing some of the negative impacts of introduced trout 
on mountain yellow-legged frog populations within a limited geographic 
area of the affected basins, providing that connectivity is restored 
between and within metapopulations.


    We are not aware of any specific county or city ordinances that 
provide protection for the Sierra Nevada population of mountain yellow-
legged frogs.
    E. Other natural or manmade factors affecting its continued 
existence. Several other natural or anthropogenically influenced 
factors, including contaminants, acid precipitation, climate change and 
drought, and ambient ultraviolet radiation, have been implicated as a 
cause of amphibian declines (Corn 1994; Alford and Richards 1999). 
These factors have been studied to varying degrees specific to the 
mountain yellow-legged frog. These factors are discussed below.
    The following factors make the mountain yellow-legged frog, along 
with other amphibians, sensitive to environmental change or 
degradation: its aquatic and terrestrial phases; its highly permeable 
skin which is exposed to substances in the water, air, and terrestrial 
substrate; and the position at which it feeds on the food web, 
depending on its life stage (Blaustein and Wake 1990, 1995; Bradford 
and Gordon 1992; Stebbins and Cohen 1995). Environmental contaminants 
have been suggested, and in some cases documented, to negatively affect 
amphibians by causing the following: direct mortality (Hall and Henry 
1992; Berrill et al. 1994, 1995; Carey and Bryant 1995; Relyea and 
Mills 2001); immune system suppression, which makes amphibians more 
vulnerable to disease (Carey 1993; Carey and Bryant 1995; Carey et al. 
1999; Daszak et al. 1999; Taylor et al. 1999); disruption of breeding 
behavior and physiology (Berrill et al. 1994; Carey and Bryant 1995, 
Hayes et al. 2002); disruption of growth or development (Hall and Henry 
1992; Berrill et al. 1993, 1994, 1995, 1998; Carey and Bryant 1995; 
Sparling et al. 2001); and disruption of the ability to avoid predation 
(Hall and Henry 1992; Berrill et al. 1993, 1994, 1995, 1998; Carey and 
Bryant 1995; Relyea and Mills 2001; Sparling et al. 2001).
    Wind-borne pesticides and the compounds that carry pesticides from 
upwind agriculture that are deposited in the Sierra Nevada have been 
suggested as a cause of measured sublethal effects to amphibians (Cory 
et al. 1971; Davidson et al. 2001; Sparling et al. 2001). In 1998, more 
than 97 million kilograms (215 million pounds) of pesticides reported 
to be used in California (CDPR 1998). Originating from the agriculture 
in California's Central Valley, and mainly from the San Joaquin Valley 
where agricultural activity is greatest, pesticides are passively 
transported eastward to the high Sierra Nevada where they have been 
detected in precipitation (rain and snow), air, dry deposition, surface 
water, plants, fish, and amphibians, including Pacific tree frogs and 
mountain yellow-legged frogs (Cory et al. 1970; Zabik and Seiber 1993; 
Aston and Seiber 1997; Datta et al. 1998; McConnell et al. 1998; LeNoir 
et al.1999; Sparling et al. 2001; Angermann et al. 2002). Angermann et 
al. (2002) detected elevated contaminant (polychlorinated biphenyls and 
toxaphene) levels in Pacific tree frog larvae within the range of the 
mountain yellow-legged frog, and suggested that these contaminants 
originate in California's Central Valley and metropolitan areas. 
Spatial analysis of populations of the California red-legged frog (Rana 
aurora draytonii), foothill yellow-legged frog, Cascades frog (R. 
cascadae), and the mountain yellow-legged frog in the Sierra Nevada 
showed a strong, statistically significant pattern of population 
decline associated with greater amounts of upwind agriculture (Davidson 
et al. 2002).
    Cholinesterase is an enzyme that functions in the nervous system 
and is disrupted by organophosphorus pesticides, including malathion, 
chlorpyrifos, and diazinon (Sparling et al. 2001). Reduced 
cholinesterase activity and pesticide residues have been found in 
Pacific treefrog larvae collected in the Sierra Nevada downwind of the 
Central Valley (Sparling et al. 2001). Cholinesterase activity was 
significantly lower in samples from the Sierra Nevada than in samples 
taken from coastal California, upwind of the Central Valley. No samples 
were taken above approximately 1,500 m (4,900 ft) elevation (Sparling 
et al. 2001), so in this study there is limited overlap with the 1,370 
to 3,650 m (4,500 to 12,000 ft) elevational range (Stebbins 1985) of 
mountain yellow-legged frogs. Although pesticide detections decrease 
with altitudinal gain, they have been detected at elevations in excess 
of 3,200 m (10,500 ft) (Zabik and Seiber 1993; Aston and Seiber 1997; 
McConnell et al. 1998; LeNoir et al. 1999; Angermann et al. 2002). In 
addition to interfering with nerve function, contaminants such as 
industrial and agricultural chemicals may act as estrogen mimics 
(Jobling et al. 1996), causing abnormalities in amphibian reproduction 
and disrupting endocrine functions (Carey and Bryant 1995; Stebbins and 
Cohen 1995; Jobling et al. 1996; Hayes et al. 2002), thereby having a 
negative effect on amphibian populations, including the mountain 
yellow-legged frog.
    In the late 1960s, dichlorodiphenyltrichloroethane (DDT)

[[Page 2301]]

and its residues were detected in significant quantities in mountain 
yellow-legged frogs and foothill yellow-legged frogs throughout the 
Sierra Nevada up to an elevation of 3,660 m (12,000 ft) (Cory et al. 
1970). The origin of this DDT is primarily attributed to agriculture in 
the Central Valley (Cory et al. 1970). DDT residues likely from 
agriculture in the Central Valley still appeared in Pacific treefrog 
larvae collected in the Sierra Nevada in the late 1990s (Sparling et 
al. 2001), more than 25 years after the use of DDT was banned in the 
United States. Levels of this toxicant in the mountain yellow-legged 
frog and foothill yellow-legged frog were significantly higher in the 
central Sierra Nevada, from the Tuolumne Meadows area of Yosemite 
National Park, north to Sonora Pass in the Stanislaus National Forest. 
The origin of DDT at these locations is attributed to two massive 
applications administered directly to this national forest and national 
park for pest control (Cory et al. 1970, 1971).
    Snow core samples from the Sierra Nevada contain a variety of 
contaminants from industrial and automotive sources, including hydrogen 
ions that are indicative of acidic precipitation, nitrogen and sulfur 
compounds (NH4, NO3, SO2, and 
SO4), and heavy metals (lead, iron, manganese, copper, and 
cadmium) (Laird et al. 1986). The pattern of recent frog extinctions in 
the southern Sierra Nevada corresponds with the pattern of highest 
concentration of air pollutants from automotive exhaust, possibly due 
to increases in nitrification (or other changes), caused by those 
pollutants (Jennings 1996). The effects of contaminants on amphibians 
need further research (Hall and Henry 1992; Briggs et al. 2002). 
However, the correlative evidence between areas of pesticide 
contamination in the Sierra Nevada and areas of amphibian decline, 
along with evidence of an adverse physiological effect from pesticides 
on amphibians in the Sierra Nevada, indicates that contaminants may 
present a risk to the mountain yellow-legged frog and may have 
contributed to the species' decline (Jennings 1996; Sparling et al. 
2001; (Davidson et al., 2002).
    It has been suggested that contamination from wind-borne pesticides 
originating from upwind agriculture, and other contaminants originating 
from metropolitan areas, may compromise amphibian immune systems (Carey 
1993; Carey et al. 1999; Daszak et al. 1999; Angermann et al. 2002). An 
effort to test the hypothesis that contaminants originating in the San 
Joaquin Valley are suppressing the mountain yellow-legged frog's immune 
system, thereby making it more vulnerable to disease, is underway 
(Briggs et al. 2002).
    Laboratory studies have documented sublethal effects on mountain 
yellow-legged frog embryos at pH 5.25 (pH represents acidity on a 
negative scale, with 7 being neutral and lower numbers indicating 
increased acidity). Survivorship of mountain yellow-legged frog embryos 
and tadpoles was negatively affected as acidity increased (at 
approximately pH 4.5 or lower), with embryos being more sensitive to 
increased acidity than tadpoles (Bradford and Gordon 1992; Bradford et 
al. 1992). Acidic deposition has been suggested as contributing to 
amphibian declines in the western United States (Blaustein and Wake 
1990; Carey 1993; Alford and Richards 1999). Other studies, however, do 
not support this hypothesis as a contributing factor to amphibian 
population declines in this area (Bradford and Gordon 1992; Bradford et 
al. 1992; Corn and Vertucci 1992; Bradford et al. 1994a, 1994b).
    Acid precipitation has been postulated as a cause of amphibian 
declines at high elevations in the Sierra Nevada because waters there 
are low in acid neutralizing capacity, and, therefore, are susceptible 
to changes in water chemistry caused by acidic deposition (Byron et al. 
1991; Bradford et al. 1994b). Near Lake Tahoe, at an elevation of 
approximately 2,100 m (6,900 ft), precipitation acidity has been 
documented to have increased significantly (Byron et al. 1991). In 
surface waters of the Sierra Nevada, acidity increases and acid 
neutralizing capacities decrease during snow melt and summer storms, 
though rarely does pH dip below 5.6 (Nikolaidis et al. 1991; Bradford 
and Gordon 1992; Bradford et al. 1998). The mountain yellow-legged frog 
breeds shortly after snow melt, thereby exposing its early life stages, 
which are most sensitive to acidification, to these conditions 
(Bradford and Gordon 1992). However, the hypothesis of acidic 
deposition as a cause of mountain yellow-legged frog declines has been 
rejected by field experiments that failed to show differences in water 
chemistry parameters between occupied and unoccupied mountain yellow-
legged frog sites (Bradford et al. 1994b).
    Extreme pH in surface waters of the Sierra Nevada is estimated at 
5.0, with most high elevation lakes having a pH of greater than 6 
(Bradford et al. 1992, 1998). Caused by oxidation of pyrite found in 
metamorphic and granitic rocks, a small number of lakes in the Sierra 
Nevada (approximately 10) are naturally acidic (Bradford et al. 1998). 
Bradford et al. (1998) found mountain yellow-legged frog tadpoles to be 
sensitive to naturally acidic conditions, and that their distribution 
was significantly related to lake acidity; they were not found in lakes 
with a pH less than 6. By contrast, the distribution of adult mountain 
yellow-legged frogs was not significantly related to natural lake 
acidity or other chemical or physical parameters. Though acidity may 
have an influence on mountain yellow-legged frog abundance or 
distribution, it is unlikely to have contributed to this species' 
decline, given the rarity of lakes acidified either by natural or 
anthropogenic sources (Bradford et al. 1998).
    The last century has included some of the most variable climate 
reversals documented, at both the annual (extremes and high frequency 
of El Ni-o (associated with severe winters) and La Ni-a (associated 
with milder winters) events) and near-decadal scales (periods of 5 to 8 
year drought and wet periods) (USDA 2001b). These events may have 
negative effects on Sierra Nevada mountain yellow-legged frogs. Severe 
winters (El Ni-o) would force longer hibernation times and could stress 
mountain yellow-legged frogs by reducing the time available for them to 
feed and breed. Alternately, during mild winters (La Ni-a), 
precipitation is reduced. This reduction in precipitation could reduce 
available breeding habitat and lead to stranding and death of frog eggs 
and tadpoles. It could also lead to increased exposure to predatory 
fish by forcing frogs into fish-containing waters if fishless waters 
dry out.
    In California, prolonged droughts are a regular occurrence to which 
native amphibians have adapted; even severe droughts are not expected 
to result in widespread population declines (Drost and Fellers 1996). 
However, an increase in the frequency, magnitude, and duration of 
droughts caused by global warming may have compounding effects with 
respect to populations of mountain yellow-legged frogs already in 
decline. In situations where other factors have resulted in the 
isolation of mountain yellow-legged frogs to marginal habitats, 
localized mountain yellow-legged frog population crashes or 
extirpations due to droughts may exacerbate their isolation and 
preclude their recolonization or immigration from other populations 
(Bradford et al. 1993; Drost and Fellers 1996).
    Changes in climate that occur faster than the ability of endangered 
species to adapt could cause local extinctions (U.S. Environmental 
Protection Agency

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(EPA) 1989). Analysis of the Antarctic Vostok ice core has shown that 
over the past 160,000 years, temperatures have varied with fluctuations 
in the concentrations of greenhouse gasses such as carbon dioxide and 
methane. Since the pre-industrial era, atmospheric concentrations of 
carbon dioxide have increased nearly 30 percent, methane concentrations 
have more than doubled, and nitrous oxide (another greenhouse gas) 
levels have risen approximately 15 percent. The burning of fossil fuels 
is the primary source of these increases. Global mean surface 
temperatures have increased 0.3-0.7 [deg]C (0.6-1.2 [deg]F)) since the 
late 19th century (EPA 1997). Climate modeling indicates that the 
overall effects of global warming on California will include higher 
average temperatures in all seasons, higher total annual precipitation, 
and decreased spring and summer runoff due to decreases in snowpacks 
(EPA 1989, 1997). Decreases in spring and summer runoff could lead to 
the loss of breeding habitat for mountain yellow-legged frogs and 
increases in instances of stranding mortality of eggs and tadpoles.
    Changes in temperature may also affect virulence of pathogens to a 
different degree than the amphibian immune systems are able to respond 
(Carey et al. 1999) and may make mountain yellow-legged frogs more 
susceptible to disease. Global warming could also affect the 
distribution of pathogens and their vectors, exposing mountain yellow-
legged frogs (potentially with weakened immune systems as a result of 
other environmental stressors) to new pathogens (Blaustein et al. 
2001). An experimental increase in stream water temperature was shown 
to decrease density and biomass in invertebrates (Hogg and Williams 
1996); thus, global warming might have a negative impact on the 
mountain yellow-legged frog prey base.
    Ambient ultraviolet-b (UV-B) radiation (280-320 nanometers (11.0-
12.6 microinches)) has increased at north temperate latitudes in the 
past two decades (Adams et al. 2001). If UV-B radiation is contributing 
to amphibian population declines, the declines would likely be greater 
at higher elevations and at more southerly latitudes where UV-B 
exposure is greatest, where the thinner atmosphere allows greater 
penetration of UV-B (Davidson et al. 2001; Davidson et al., 2002). In 
California, where there is a north-to-south gradient of increasing UV-B 
exposure, amphibian declines would also likely be more prevalent at 
southerly latitudes (Davidson et al. 2001; Davidson et al., 2002). 
Melanic pigment on the upper surfaces of amphibian eggs and larvae 
protects these sensitive life stages against UV-B damage, an important 
protection for normal development of amphibians exposed to sunlight, 
especially at high elevations in clear and shallow waters (Stebbins and 
Cohen 1995). Blaustein et al. (1994c) observed decreased hatching 
success in several species of amphibian embryos (the mountain yellow-
legged frog was not tested) exposed to increased UV-B radiation, 
indicating that this may be a cause of amphibian declines. Juveniles 
and adults may be exposed to increased UV-B levels as they heat 
themselves by basking in the sun (Stebbins and Cohen 1995). In a 
spatial test of the hypothesis that UV-B has contributed to decline of 
the mountain yellow-legged frog in the Sierra Nevada, Davidson et al. 
(2002) concluded that patterns of this species decline are inconsistent 
with the predictions of where UV-B related population declines would 
occur. Greater numbers of extant populations of this species were 
present at higher elevations than at lower elevations, and population 
decline was greater in the northern portion of the range of this 
species than it was in the southern portion. Though it does not appear 
that UV-B is a factor in the decline of the mountain yellow-legged 
frog, the absence of the predicted pattern for UV-B-caused decline 
should not be taken as proof that UV-B is not affecting the mountain 
yellow-legged frogs, given the potential for one or more factors that 
cause population declines to mask other factors (Davidson et al., 


    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by this species. We reviewed the petition, information available 
in our files, other published and unpublished information submitted to 
us during the public comment period following our 90-day petition 
finding, and consulted with recognized mountain yellow-legged frog 
experts and other Federal and State resource agencies. On the basis of 
the best scientific and commercial information available, we find that 
listing the Sierra Nevada DPS of the mountain yellow-legged frog is 
warranted, but is precluded by higher priority listing actions.
    In making this finding, we recognize that there have been declines 
in the distribution and abundance of the Sierra Nevada DPS of the 
mountain yellow-legged frog, primarily attributed to the introduction 
and subsequent predation of non-native fishes, as documented in the 
body of scientific research on the distributions of introduced trout in 
relation to mountain yellow-legged frogs (Bradford 1989; Bradford et 
al. 1993, 1994a, 1998; Knapp 1994, 1996; Drost and Fellers 1996; Knapp 
and Matthews 2000; Knapp et al. 2001). Direct predation of non-native 
fishes on mountain yellow-legged frogs has resulted in range-wide 
population declines and local extirpations. Furthermore, the result of 
these extirpations is that the remaining populations are fragmented and 
isolated, making them vulnerable to further declines and local 
extirpations from other factors. Populations that go extinct following 
habitat fragmentation and populations isolation are unlikely to be 
recolonized due to both the isolation from, and lack of, habitat 
connectivity to potential source populations.
    For example, in reviewing documented mountain yellow-legged frog 
declines over the last 5 years in Sequoia and Kings National Parks, we 
found a 39 percent extinction rate of the frog where fish have not been 
stocked since the late 1970s. In comparison, over the last 7 years in 
the Sierra National Forest's John Muir Wilderness Area, there has been 
a 61 percent extinction rate where fish stocking has continued. This 
high rate of extinction over a 5 to 7 year time frame suggests the 
species' extinction within a few decades (assuming that the rate of 
extinction and recolonization observed over this time period accurately 
reflects the long-term rates) (R. Knapp, in litt. 2002.).
    The isolation of remaining mountain yellow-legged frog populations 
and habitat fragmentation as a result of non-native fish introductions 
has made remaining populations vulnerable to extinction from random 
events such as disease. Disease has only recently been recognized as an 
important factor in the decline of this species. It appears, however, 
that disease will continue to play an important role in the decline of 
this species. It is likely that disease, specifically chytrid fungus, 
has contributed to the recently observed declines in Sequoia and Kings 
Canyon National Parks and in the Sierra National Forests's John Muir 
Wilderness Area (R. Knapp, in litt. 2002). Although the life history 
and modes of transmission of chytrid fungus are not well understood, it 
appears that this pathogen is widespread throughout the range of the 
mountain yellow-legged frog within the Sierra Nevada, it is persistent 
in ecosystems, and it is

[[Page 2303]]

resilient to environmental conditions such as drought and freezing. 
Therefore, we conclude that all remaining yellow-legged frog 
populations within the Sierra Nevada are at risk to declines and 
extirpation as a result of infection by this pathogen.
    Other factors include airborne contaminants, habitat degradation 
(mainly as a result of livestock grazing) and the inadequacy of 
existing regulatory mechanisms. Each of these factors may contribute to 
mountain yellow-legged frog population declines or extirpations. In 
addition, these factors are exacerbated by the effects that have been 
caused by non-native fishes, specifically the isolation of remaining 
mountain yellow-legged frog populations and habitat fragmentation. As 
noted previously, populations that go extinct following habitat 
fragmentation and population isolation are unlikely to be recolonzied 
due to both the isolation from, and lack of, connectivity to potential 
source populations.
    We conclude that the overall magnitude of threats to the Sierra 
Nevada DPS of the mountain yellow-legged frog is high, and that the 
overall immediacy of these threats is imminent. Pursuant to our Listing 
Priority System (64 FR 7114), a DPS of a species for which threats are 
high and imminent is assigned a Listing Priority Number of 3. While we 
conclude that listing the Sierra Nevada DPS of the mountain yellow-
legged frog is warranted, an immediate proposal to list is precluded by 
other higher priority listing actions. During Fiscal Year 2003 we must 
spend nearly all of our Listing Program funding to comply with court 
orders and judicially approved settlement agreements, which are now our 
highest priority actions. To the extent that we have discretionary 
funds, we will give priority to using them to address emergency 
listings and listing actions for other species with a higher priority. 
Due to litigation pertaining to various listing actions, our planned 
work with listing funds in Fiscal Year 2003 consists primarily of 
addressing court-ordered actions, court-approved settlement agreements, 
and listing actions that are in litigation. (Also, some litigation-
related listing actions already are scheduled for Fiscal Year 2004.) We 
expect that our discretionary listing activity in Fiscal Year 2003 will 
focus on addressing our highest priority listing actions of finalizing 
expiring emergency listings.
    The Sierra Nevada DPS of the mountain yellow-legged frog will be 
added to the list of candidate species upon publication of this notice 
of 12-month finding. We will continue to monitor the status of this 
species and other candidate species. Should an emergency situation 
develop with one or more of the species, we will act to provide 
immediate protection, if warranted.
    We intend that any proposed listing action for the Sierra Nevada 
DPS of the mountain yellow-legged frog will be as accurate as possible. 
Therefore, we will continue to accept additional information and 
comments from all concerned governmental agencies, the scientific 
community, industry, or any other interested party concerning this 

References Cited

    A complete list of all references cited is available on request 
from the Sacramento Fish and Wildlife Office (see ADDRESSES section, 


    The primary author of this document is Peter Epanchin of the 
Sacramento Fish and Wildlife Office (see FOR FURTHER INFORMATION 
CONTACT section).

    Authority:  The authority for this action is the Endangered 
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: January 10, 2003.
Marshall P. Jones, Jr.,
Director, Fish and Wildlife Service.
[FR Doc. 03-973 Filed 1-15-03; 8:45 am]