[Federal Register: December 22, 1999 (Volume 64, Number 245)]
[Proposed Rules]               
[Page 71714-71722]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AF83

Endangered and Threatened Wildlife and Plants: Proposed 
Endangered Status for the Southern California Distinct Vertebrate 
Population Segment of the Mountain Yellow-Legged Frog

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.


SUMMARY: We, the Fish and Wildlife Service (Service), propose to list 
the southern California distinct vertebrate population segment (DPS) of 
mountain yellow-legged frog (Rana muscosa) as endangered, pursuant to 
the Endangered Species Act of 1973, as amended (Act). In southern 
California, this DPS has been reduced to only a few isolated remnants 
in the San Gabriel, San Jacinto, and San Bernardino Mountains. 
Hypothesized causes of the decline include predation from introduced 
trout or possibly some other widespread environmental effects such as 
airborne contaminants. These effects have probably acted in combination 
to produce the decline. The chronology of the decline is not well 
documented, but it appears that a precipitous decline occurred over the 
last three or four decades. The decline went largely unnoticed and was 
not studied. In addition to predation from trout and other widespread 
factors, the few remaining frogs are now threatened by recreational 
suction dredging for gold and human activities at campgrounds and day 
use areas. The remnant populations are so small that they are now at 
risk from random genetic, demographic, and environmental effects as 
well. This proposed rule constitutes the 12-month finding on a petition 
to list the southern California population of mountain yellow-legged 
frog as threatened or endangered. This proposed rule, if made final, 
would implement the Federal protection and recovery provisions afforded 
by the Act for this DPS. We welcome data and comment from the public on 
this proposal.

DATES: You must submit any comments by February 22, 2000 and public 
hearing requests by February 7, 2000.

ADDRESSES: You may send comments and materials concerning this proposal 
to the Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish 
and Wildlife Office, 2730 Loker Avenue West, Carlsbad, California 
92008. You may inspect comments and materials received, by appointment, 
during normal business hours at the above address.

FOR FURTHER INFORMATION CONTACT: Ken Berg at the above address 
(telephone 760/431-9440).



    The mountain yellow-legged frog is a true frog in the family 
Ranidae. Mountain yellow-legged frogs were originally described by Camp 
in 1917 (as cited by Zweifel 1955) as a subspecies of Rana boylii. 
Zweifel (1955) demonstrated that frogs from the high Sierra and the 
mountains of southern California were somewhat similar to each other 
yet were distinct from the rest of the R. boylii (=boylei) group. Since 
that time, most authors have followed Zweifel, treating the mountain 
yellow-legged frog as a full species, Rana muscosa.
    Mountain yellow-legged frogs are moderately sized, about 40 to 80 
millimeters (mm) (1.5 to 3 inches (in)) from snout to urostyle (the 
pointed bone at the base of the backbone) (Jennings and Hayes 1994; 
Zweifel 1955). The pattern is variable, ranging from discrete dark 
spots that can be few and large, to smaller and more numerous spots 
with a mixture of sizes and shapes, to irregular lichen-like patches or 
a poorly defined network (Zweifel 1955). The body color is also 
variable, usually a mix of brown and yellow, but often with gray, red, 
or green-brown. Some individuals may be dark brown with little pattern 
(Jennings and Hayes 1994). The back half of the upper lip is pale. 
Folds are present on each side of the back, but usually they are not 
prominent (Stebbins 1985). The throat is white or yellow, sometimes 
with mottling of dark pigment (Zweifel 1955). The belly and 
undersurface of the high limbs are yellow, which ranges in hue from 
pale lemon yellow to an intense sun yellow. The iris is gold with a 
horizontal, black counter shading stripe (Jennings and Hayes 1994).
    In the Sierra Nevada Mountains of California, the mountain yellow-
legged frog ranges from southern Plumas County to southern Tulare 
County (Jennings and Hayes 1994), at elevations

[[Page 71715]]

mostly above 1,820 meters (m) (6,000 feet (ft)). The frogs of the 
Sierra Nevada are isolated from the frogs of the mountains of southern 
California by the Tehachapi Mountains and a distance of about 225 
kilometers (km) (140 miles (mi)). The southern California frogs now 
occupy portions of the San Gabriel, San Bernardino, and San Jacinto 
Mountains. Zweifel (1955) noted the presence of an isolated southern 
population on Mt. Palomar in northern San Diego County, but this 
population appears to be extinct (Jennings and Hayes 1994). In southern 
California, the elevation range reported by Stebbins (1985) is 182 m 
(600 ft) to 2,273 m (7,500 ft). Representative localities, including 
some that are no longer occupied, which demonstrate the wide elevation 
range that mountain yellow-legged frogs inhabited in southern 
California, include Eaton Canyon, Los Angeles County (370 m (1,220 ft)) 
and Bluff Lake, San Bernardino County (2,290 m (7,560 ft)). The 
southern California locations now occupied by mountain yellow-legged 
frogs range from City Creek, in the San Bernardino Mountains (760 m 
(2,500 ft)), to Dark Canyon in the San Jacinto Mountains (1,820 m 
(6,000 ft)).
    Southern California mountain yellow-legged frogs are diurnal, 
highly aquatic frogs, occupying rocky and shaded streams with cool 
waters originating from springs and snowmelt. In these areas, juveniles 
and adults feed on small, streamside arthropods (Jennings and Hayes 
1994). They do not occur in the smallest creeks. The coldest winter 
months are spent in hibernation, probably under water or in crevices in 
the bank. Mountain yellow-legged frogs emerge from overwintering sites 
in early spring, and breeding soon follows. Eggs are deposited in 
shallow water where the egg mass is attached to vegetation or the 
substrate. In the Sierra Nevada, larvae select warm microhabitats 
(Bradford 1984 cited in Jennings and Hayes 1994), and the time to 
develop from fertilization to metamorphosis reportedly varies from 1 to 
2.5 years (Jennings and Hayes 1994).
    Prior to the late 1960s, mountain yellow-legged frogs were abundant 
in many southern California streams (G. Stewart, in litt. 1995), but 
they now appear to be absent from most places in which they previously 
occurred. Jennings and Hayes (1994) believe that mountain yellow-legged 
frogs are now absent from more than 99 percent of their previous range 
in southern California. This decline is part of a well-known larger 
pattern of declines among native ranid frogs in the western United 
States (Hayes and Jennings 1986; Drost and Fellers 1996). Some of the 
western ranid frog species experiencing noticeable declines are the 
California red-legged frog (Rana aurora draytonii) (61 FR 25813), the 
spotted frog (R. pretiosa and R. luteventris), the Cascades frog (R. 
cascadae), and the Chiricahua leopard frog (R. chiricauhensis) (62 FR 
49398). Nowhere have the declines been any more pronounced than in 
southern California, where, besides declines in mountain yellow-legged 
frogs, the California red-legged frog has been reduced to a few small 
remnants (61 FR 25813), and the foothill yellow-legged frog (R. boylii) 
may be extinct (Jennings and Hayes 1994.)
    The mechanisms causing the declines of western frogs are not well 
understood and are certain to vary somewhat among species, but the two 
most common and well-supported hypotheses for widespread declines of 
western ranid frogs are: (1) Past habitat destruction related to 
unregulated activities such as logging and mining and more recent 
habitat conversions for water development, irrigated agriculture, and 
commercial development (Hayes and Jennings 1986; 61 FR 25813); and (2) 
alien predators and competitors (Bradford 1989; Knapp 1996; Kupferberg 
1997). Natural populations may be killed off directly by these factors 
operating alone or in combination, or these factors so severely disrupt 
the normal population dynamics that when local extinctions occur, 
regardless of the cause, natural recolonization is impossible. Other 
environmental factors that could have adverse effects over a wide 
geographic range include pesticides, certain pathogens, and 
ultraviolet-B (beyond the visible spectrum) radiation, but their role, 
if any, in amphibian declines is not well understood (Reaser 1996). 
These factors, acting singly or in combination, may be contributing to 
widespread, systematic declines of western ranid frogs. Determining 
their effects, however, is not an easy task (Reaser 1996; Wake 1998), 
and the Department of the Interior (USDOI) currently supports an 
initiative to fund research on the causes of amphibian declines (see 
examples in USDOI 1998).
    Some of the same factors that are hypothesized to have caused 
declines of other western ranid frogs are likely to be responsible for 
the reduction of the mountain yellow-legged frog in southern 
California. Because the declines have been so precipitous, and have 
spared only a small number of frogs in a few localities, the factors, 
and their interactions, that caused the decline may never be fully 
understood. We believe that these factors are still operating, and 
unless reversed, a high probability exists that this frog may be 
extinct in southern California within a few decades. In the case of the 
mountain yellow-legged frog, the only factor listed above that we 
believe can be ruled out as a likely cause of decline is habitat 
destruction related to activities such as logging, mining, irrigated 
agriculture, and commercial development. The range of the mountain 
yellow-legged frog in southern California is mainly on public land 
administered by the U.S. Forest Service (FS). Most of the rugged 
canyons and surrounding mountainous terrain have been altered little 
and look much the same today as they did when earlier naturalists such 
as Lawrence Klauber collected mountain yellow-legged frogs there in the 
early decades of the 1900s.

Current Range and Status

    In southern California, mountain yellow-legged frogs can still be 
found in four small streams in the San Gabriel Mountains, the upper 
reaches of the San Jacinto River system in the San Jacinto Mountains, 
and at a single locality on City Creek, a tributary of the Santa Ana 
River, in the San Bernardino Mountains (Jennings and Hayes 1994; M. D. 
Wilcox in litt., 1998). These areas along with the numbers of frogs 
most recently observed in each area are described below.
    San Gabriel Mountains: Surveys conducted from 1993 to 1997 revealed 
small isolated populations in the upper reaches of Prairie Creek/
Vincent Gulch, Devil's Canyon, and Alder Creek/East Fork, on the East 
Fork of the San Gabriel River, and Little Rock Creek on the Mojave 
River (Jennings and Hayes 1994 and references therein; Jennings 1995; 
Jennings 1998). The surveys involved one to three field biologists and 
were conducted over 1-5 days per site. Over the course of these field 
studies, 15 adults or fewer were observed at any 1 site, and, after the 
1995 season, Jennings (1995) concluded that the actual population at 
each of the sites was only 10-20 adults.
    San Jacinto Mountains: Small populations of mountain yellow-legged 
frogs also occur in four tributaries in the upper reaches of the North 
Fork, San Jacinto River on Mount San Jacinto: Dark Canyon, Hall Canyon, 
Fuller Mill Creek, and the main North Fork, San Jacinto River (Jennings 
and Hayes 1994; Jennings 1995; Jennings 1998). The number of frogs 
occupying these sites is not known, but fewer than 10 adult frogs per 
site per year have been observed in surveys from 1995 to the present.
    San Bernardino Mountains: A few tadpoles and 26 recently 

[[Page 71716]]

juveniles, but no adults, were rediscovered on a roughly 1-mile reach 
of the East Fork, City Creek during the summer of 1998 (M. D. Wilcox in 
litt., 1998). Previous to this finding, mountain yellow-legged frogs 
had not been observed in the San Bernardino Mountains since the 1970s 
(Jennings and Hayes 1994), even though surveys were conducted during 
the summer and fall of 1997 and 1998 (Holland 1997; Tierra Madre 1999).
    When frogs were encountered during field surveys accomplished 
between 1988 and 1995, only a few individuals were observed. Jennings 
and Hayes (1994) and Jennings (1995) suggested that the entire 
population of mountain yellow-legged frogs in the San Gabriel and San 
Jacinto Mountains (8 more or less isolated sites) was probably fewer 
than 100 adult frogs. Their rough estimate is based on a compilation of 
the results of visual surveys generally conducted on a single day, not 
on formal population abundance estimation techniques. While the precise 
number of adult frogs may be greater than 100, we concur with Jennings 
and Hayes (1994) that, in the San Gabriel and San Jacinto Mountains, 
the available data indicate that this once widespread species is now 
found in only a small number of relatively isolated populations. We do 
not know the population size of adult frogs at the recently 
rediscovered site on the east fork of City Creek in the San Bernardino 
Mountains, but because no adults and only a few juveniles and tadpoles 
were encountered, the adult population is probably small. Thus, we 
conclude that each of the three mountain ranges (San Gabriel, San 
Jacinto, San Bernardino) contains a small number of small, relatively 
isolated populations.

Distinct Vertebrate Population Segment

    We analyzed the mountain yellow-legged frog according to the joint 
Service and National Marine Fisheries Service Policy Regarding the 
Recognition of Distinct Vertebrate Populations, published in the 
Federal Register on February 7, 1996 (61 FR 4722). We consider three 
elements in determining whether a vertebrate population segment could 
be treated as threatened or endangered under the Act: discreteness, 
significance, and conservation status in relation to the standards for 
listing. Discreteness refers to the isolation of a population from 
other members of the species and is based on two criteria: (1) Marked 
separation from other populations of the same taxon resulting from 
physical, physiological, ecological, or behavioral factors, including 
genetic discontinuity, or (2) populations delimited by international 
boundaries. We determine significance either by the importance or 
contribution, or both, of a discrete population to the species 
throughout its range. Our policy lists four examples of factors that 
may be used to determine significance: (1) Persistence of the discrete 
population segment in an ecological setting unusual or unique for the 
taxon; (2) evidence that loss of the discrete population segment would 
result in a significant gap in the range of the taxon; (3) evidence 
that the discrete population segment represents the only surviving 
natural occurrence of the taxon that may be more abundant elsewhere as 
an introduced population outside its historic range; and (4) evidence 
that the discrete population segment differs markedly from other 
populations of the taxon in its genetic characteristics. If we 
determine that a population segment is discrete and significant, we 
evaluate it for endangered or threatened status based on the Act's 
    Discreteness: The range of the mountain yellow-legged frog is 
divided by a natural geographic barrier, the Tehachapi Mountains, which 
isolate Sierran frogs from those in the mountains of southern 
California. The distance of the separation is about 225 km (140 mi), 
but the separation may not have been this great in the recent past 
because a frog collected in 1952 on Breckenridge Mountain in Kern 
County was identified by Jennings and Hayes (1994) as a mountain 
yellow-legged frog. The geographic separation of the Sierran and 
southern California frogs was recognized in the earliest description of 
the species by Camp (1917, cited in Zweifel 1955), who treated frogs 
from the two localities as separate subspecies within the R. boylii 
group. He designated the Sierran frogs R. b. sierrae and the southern 
California frogs R. b. muscosa, based on geography and subtle 
morphological differences. Zweifel (1955) reevaluated the morphological 
evidence and found it insufficient to warrant Camp's recognition of two 
subspecies, the chief difference between the two being hind-limb 
    More recently, Ziesmer (1997) analyzed the calls of Sierran (Alpine 
and Mariposa Counties) and southern California (San Jacinto Mountains 
and Riverside County) mountain yellow-legged frogs. He found that the 
calls of Sierran frogs differed from southern California frogs in pulse 
rate, harmonic structure, and dominant frequency. Based on a limited 
sample, Ziesmer concluded that the results supported the hypothesis 
that mountain yellow-legged frogs from the Sierra Nevada and southern 
California are separate species.
    Allozyme (a form of an enzyme produced by a gene) variation 
throughout the range of the mountain yellow-legged frog has been 
examined, but the results are open to interpretation (Jennings and 
Hayes 1994 and references therein). In the work most applicable to the 
question of the distinctiveness of the Sierran and southern California 
frogs, David Green (pers. comm., 1998) analyzed allozyme variation in 
central Sierran mountain yellow-legged frogs (four individuals, 
Tuolumne County) and southern California mountain yellow-legged frogs 
(two individuals, Riverside County). He found fixed differences at 6 of 
28 loci (sites on a chromosome occupied by specific genes). These 
limited, unpublished data suggest that Sierran and southern California 
mountain yellow-legged frogs are different at a level that could 
support the recognition of full species. However, because of the small 
number of individuals per sample and the limited number of samples, we 
view these results cautiously. It is possible that existing variation 
at those six loci may not have been detected with such a small number 
of individuals sampled. To better understand whether a genetic 
discontinuity significant enough to warrant full species rank exists 
between Sierran frogs and those from the mountains of southern 
California, samples of frogs from the southern Sierra Nevada, 
especially the Greenhorn Mountains, would be of particular interest.
    Although Green's limited allozyme analysis may not be sufficient to 
support recognizing the Sierran and southern California populations as 
separate species, it does support the conclusion of significant 
geographic separation. This conclusion is also supported by earlier 
observations of morphological differences (Zweifel 1955, and references 
therein) and differences in vocalizations (Ziesmer 1997). Considered 
together, the evidence supports an interpretation of isolation between 
the two populations of frogs over a very long period. We find that the 
southern California frogs meet the criterion of ``marked separation 
from other populations of the same taxon'' and qualify as discrete 
according to the Policy Regarding the Recognition of Distinct 
Vertebrate Populations (61 FR 4722).
    Significance: One of the most striking differences between Sierran 
and southern California mountain yellow-legged frogs is the habitats 
they occupy. Zweifel (1955) observed that the frogs in southern 
California are typically found

[[Page 71717]]

in steep gradient streams in the chaparral belt, even though they may 
range up into small meadow streams at higher elevations. In contrast, 
Sierran frogs are most abundant in high elevation lakes and slow-moving 
portions of streams. Bradford's (1989) southern Sierra Nevada study 
site, for example, was in Sequoia and Kings Canyon National Parks at 
high elevations (between 2,910-3,430 m (9,600-11,319 ft)). The rugged 
canyons of the arid mountain ranges of southern California bear little 
resemblance to the alpine lakes of the Sierra Nevada. On the basis of 
habitat alone, one might easily conclude that these are two very 
different frogs.
    The mountain yellow-legged frogs of southern California comprise 
the southern portion of the species' range. The extinction of this 
southern group would be significant because it would substantially 
reduce the overall range as it is currently understood, and what is now 
a gap in the distribution, the Tehachapi Mountains, would become the 
southern limit of the species' range.
    In addition, evidence exists that the mountain yellow-legged frog 
is not simply a single species with a disjunct distribution (cited in 
Zweifel 1955; Stebbins 1985). As discussed above, vocal and genetic 
differences exist between Sierran and southern California mountain 
yellow-legged frogs. Although the data are limited and some important 
variation may have been missed, they are consistent with the earlier 
interpretation by Camp (1917 cited in Zweifel 1955) and numerous other 
authors prior to Zweifel (e.g., Stebbins 1954) who treated the two 
forms as taxonomically distinct. If the differences in vocalization 
described by Ziesmer (1997) and the allozyme variation described by 
Green (per. comm., 1998) accurately characterize differences between 
the two forms, then the Sierran and southern California frogs are quite 
different and have been isolated for a very long time.
    Our conclusion that Sierran and southern California frogs are very 
different from each other, and may even merit recognition as separate 
subspecies or possibly even species, is based on the cumulative weight 
of the available evidence. We find that the mountain yellow-legged 
frogs inhabiting the mountains of southern California meet the 
significance criteria under our Policy Regarding the Recognition of 
Distinct Vertebrate Populations (61 FR 4722) on the basis of the 
geographical, ecological, vocal, and genetic discontinuities described 
    In the remainder of this proposed rule, we evaluate the southern 
California mountain yellow-legged frog for endangered status based on 
the Act's standards. For clarity, we refer to all mountain yellow-
legged frogs south of the Tehachapi Mountains as the southern 
California DPS. We use the word ``population'' to describe all of the 
frogs living in a particular place.

Previous Federal Action

    On July 13, 1995, we received a petition dated July 10, 1995, from 
D.C. ``Jasper'' Carlton (of the Biodiversity Legal Foundation), Bonnie 
M. Dombrowski, and Michael C. Long to list as threatened or endangered 
the southern California populations of the mountain yellow-legged frog 
(Rana muscosa) pursuant to the Act. Accompanying the petition was 
supporting information related to the taxonomy, ecology, and the past 
and present distribution of the species. We reviewed the petition, 
supporting documentation, and other information cited in this proposed 
rule to determine if substantial information was available to indicate 
that the requested action may be warranted. On July 8, 1997, we 
published a 90-day finding for the petition to list the southern 
California populations of the mountain yellow-legged frog (62 FR 
36481). We found the southern California population to be a DPS and 
furthermore found the petition presented substantial information 
indicating the listing of the species (DPS) may be warranted. Once we 
made the finding that the petition presented substantial information, 
we commenced a status review pursuant to section 4(b)(3)(A) of the Act. 
However, consistent with the applicable Listing Priority Guidances (62 
FR 55268; 63 FR 25502), our Carlsbad Field Office completed work on 
higher priority listing actions before completing this 12-month finding 
and proposed rule to list this DPS of the mountain yellow-legged frog.
    The processing of this proposed rule conforms with our Listing 
Priority Guidance published in the Federal Register on October 22, 1999 
(64 FR 57114). The guidance clarifies the order in which we will 
process rulemakings. Highest priority is processing emergency listing 
rules for any species determined to face a significant and imminent 
risk to its well-being (Priority 1). Second priority (Priority 2) is 
processing final determinations on proposed additions to the lists of 
endangered and threatened wildlife and plants. Third priority is 
processing new proposals to add species to the lists. The processing of 
administrative petition findings (petitions filed under section 4 of 
the Act) is the fourth priority. The processing of critical habitat 
determinations (prudency and determinability decisions) and proposed or 
final designations of critical habitat will be funded separately from 
other section 4 listing actions and will no longer be subject to 
prioritization under the Listing Priority Guidance. The processing of 
this proposed rule is a Priority 3 action.

Summary of Factors Affecting the Species

    Section 4 of the Endangered Species Act (16 U.S.C. 1531 et seq.) 
and the regulations (50 CFR part 424) that implement the listing 
provisions of the Act set forth the procedures for adding species to 
the Federal lists. A species may be determined to be an endangered or 
threatened species due to one or more of the five factors described in 
section 4(a)(1). These factors and their application to the southern 
California DPS of mountain yellow-legged frogs are as follows:

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

    All nine known populations of southern California Rana muscosa 
occur on lands owned and managed by the FS and are clustered within 
three drainages, one in the San Gabriel Mountains, one in the San 
Bernardino Mountains, and another on Mount San Jacinto. As such, the 
habitats in which they live are protected against wholesale conversions 
to other uses. However, with so few populations remaining, and with 
each of those numbering only a few individuals, localized habitat 
alterations, which would not be appreciable if the DPS were more wide-
ranging and abundant, threaten the DPS. Local habitat changes caused by 
recreational suction dredging for gold and human use around 
campgrounds, picnic grounds, and heavily used trails may harm the 
habitat and contribute to local extinctions wherever these activities 
intersect with mountain yellow-legged frogs.
    Jennings (1995) observed suction dredging within the Wilderness 
Area where mountain yellow-legged frogs occur on the East Fork, San 
Gabriel River. He reported observing large quantities of trash and 
toxic materials being dumped into the stream bed. If this practice is 
continued, it could have harmful effects on the population inhabiting 
the East Fork, San Gabriel River. The consequences for populations on 
other San Gabriel River tributaries is difficult to predict, but any 
losses would further isolate the remaining populations and probably

[[Page 71718]]

reduce the time to extinction for the DPS. Other than the East Fork, 
San Gabriel River site, we do not know if recreational gold mining 
occurs or at what level on or near sites occupied by frogs. Extensive 
suction dredging activity at or near a breeding site could have the 
harmful effect of killing eggs or larvae or changing the hydrology, 
rendering it unsuitable for breeding. Some of the habitat effects of 
suction dredging on streams are described by Harvey (1986), who found 
dredging altered substrates and changed the habitat for fish and 
    Fairly heavy camping and day use coincides with frog habitat along 
the East Fork, San Gabriel River (dispersed camping), Prairie Fork 
Creek (campground, recently burned and presently closed by the FS), 
Little Rock Creek (trail, rock climbing), Dark Canyon (campground), and 
Fuller Mill Creek (picnic ground). In areas occupied by frogs, human 
presence in and along streams can disrupt the lives of eggs, larvae, 
and adult frogs and change the entire character of the stream and its 
bank and associated vegetation in ways that make whole sections of 
stream less suitable for frogs. Only nine very small populations 
remain, and at least four of these are in areas that receive reasonably 
heavy human camping or day use. The loss of even small numbers of frogs 
from any of these populations due to human camping or day use, either 
alone or in combination with other factors, will increase the 
probability of local extinction. Any local extinctions will further 
isolate the remaining populations and probably reduce the time to 
extinction for the DPS.

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

    Numerous museum specimens from many localities (Jennings and Hayes 
1994) attest to the fact that, for decades, mountain yellow-legged 
frogs from the southern DPS have been collected for scientific 
purposes. These collections probably did not have an appreciable 
effect. Now that the DPS has declined precipitously, populations are so 
few in number, and the size of each population is so small, very little 
or no scientific collecting of the southern DPS occurs. Collecting, 
scientific or amateur, if it did occur, could seriously increase the 
probability of extinction of any of the remaining populations. Any 
local extinctions will further isolate the remaining populations and 
probably reduce the time to extinction for the DPS.

C. Disease or Predation

    Predation by introduced trout, including rainbow trout 
(Oncorhynchus mykiss), is one of the best documented causes of the 
decline of Sierran mountain yellow-legged frogs. Careful study of the 
distributions of introduced trout and mountain yellow-legged frogs for 
several years has shown conclusively that introduced trout have had 
negative impacts on mountain yellow-legged frogs over much of the 
Sierra Nevada (Bradford 1989; Knapp 1996). Bradford (1989) and Bradford 
et al. (1993) concluded that introduced trout eliminate many 
populations of mountain yellow-legged frogs and the presence of trout 
in intervening streams sufficiently isolates other frog populations so 
that recolonization after stochastic (random, naturally occurring) 
local extinctions is essentially impossible. This mechanism is 
sufficient to explain the elimination of Sierran mountain yellow-legged 
frogs from the majority of sites they once inhabited, and, alone or in 
combination with other factors, introduced trout have almost certainly 
contributed to the widespread and systematic decline of the southern 
DPS as well.
    Virtually all streams in the mountains of southern California 
contain populations of introduced rainbow trout, and trout are 
routinely planted in Dark Canyon, Fuller Mill Creek in the San Jacinto 
Mountains, and City Creek in the San Bernardino Mountains. Most of the 
other streams still occupied by mountain yellow-legged frogs have 
histories of trout introductions and probably contain naturally 
reproducing, sustainable populations at, or very near, the sites 
occupied by the frogs. Wherever the two species co-occur, trout are 
likely to eliminate mountain yellow-legged frogs or keep populations 
low and limit dispersal. The widespread occurrence of introduced trout 
in the mountains of southern California may make it very difficult to 
reverse the decline to extinction of the DPS.
    Another introduced predator that could have effects on the DPS 
similar to those of the trout, yet on a more limited scale, is the 
bullfrog, Rana catesbeiana. Bullfrogs have been listed among the 
threats to other western frogs (61 FR 25813; Kiesecker and Blaustein 
1998) and toads (59 FR 64859). Bullfrogs are now widespread in southern 
California and occur in many drainages formerly and currently occupied 
by mountain yellow-legged frogs. The negative effects of bullfrogs on 
mountain yellow-legged frogs in the mountains of southern California 
are probably less widespread than those of introduced trout because 
there is less overlap in their occurrence. Any habitat alterations that 
are favorable to bullfrogs, however, will cause them to become abundant 
locally. In areas where mountain yellow-legged frogs occur, this 
increase could lead to local extinctions and increased isolation of the 
remaining populations, which would probably reduce the time to 
extinction for the entire DPS.
    Bradford (1991) documented the loss of a Sierran population of Rana 
muscosa due to the combined effect of ``red-leg'' disease (caused by 
the bacterium Aeromonas hydrophila) and predation by Brewer's 
blackbirds, Euphagus cyanocephalus. Another pathogen that is generating 
concern among those who study amphibian declines is the chytrid fungus. 
Chytrids may be seriously affecting amphibians in many places around 
the world, and they have recently been discovered on larval mountain 
yellow-legged frogs in the Sierra Nevada (Gary Fellers, pers. comm. 
1999). Because of the small and isolated nature of the remaining 
populations, disease could be serious. Any local extinctions caused by 
disease would further isolate the remaining populations and probably 
reduce the time to extinction for the entire DPS.

D. The Inadequacy of Existing Regulatory Mechanisms

    Existing regulatory mechanisms have not stopped the decline of 
mountain yellow-legged frogs in southern California. Existing 
regulatory mechanisms that could provide some protection for the 
mountain yellow-legged frog include: (1) Consideration under the 
California Environmental Quality Act (CEQA); (2) consideration under 
section 404 of the Clean Water Act (CWA); and (3) co-occurrence with 
other species protected by the Endangered Species Act of 1973.
    The State of California considers mountain yellow-legged frogs a 
species of special concern, but it is not a threatened or endangered 
species and receives no protection under the California Endangered 
Species Act. California Sport Fishing Regulations include the mountain 
yellow-legged frog as a protected species that may not be taken or 
possessed at any time except under special permit from the California 
Department of Fish and Game. This prohibition may help prevent threats 
from collecting, but this threat is not a significant cause of the 
decline, and the DPS is expected to continue declining toward 
extinction even in the absence of collecting.
    The CEQA requires a full public disclosure of the potential 
environmental impact of proposed

[[Page 71719]]

projects. The public agency with primary authority or jurisdiction over 
the project is designated as the lead agency and is responsible for 
conducting a review of the project and consulting with other agencies 
concerned with resources affected by the project. Section 15065 of the 
CEQA guidelines require a finding of significance if a project has the 
potential to ``reduce the number or restrict the range of a rare or 
endangered plant or animal.'' Species that are eligible for listing as 
rare, threatened, or endangered but are not so listed are given the 
same protection as those species that are officially listed with the 
State. Once significant impacts are identified, the lead agency has the 
option to require mitigation for effects through changes in the project 
or to decide that overriding considerations make mitigation infeasible. 
In the latter case, projects may be approved that cause significant 
environmental damage, such as destruction of endangered species. 
Protection of listed species through CEQA is, therefore, at the 
discretion of the lead agency involved. The CEQA provides that, when 
overriding social and economic considerations can be demonstrated, 
project proposals may go forward, even in cases where the continued 
existence of the species may be threatened, or where adverse impacts 
are not mitigated to the point of insignificance.
    Besides the Act, the primary Federal law that potentially affords 
some protection for the mountain yellow-legged frog is section 404 of 
the CWA. The CWA may provide some general protections for species, 
however, this DPS has declined precipitously under this Federal law.
    The arroyo toad (Bufo microscaphus californicus), a federally 
listed endangered species, is present in the San Gabriel Mountains, but 
there is no benefit to the mountain yellow-legged frog because the two 
species occupy different areas in the San Gabriel Mountains and the 
arroyo toads are not known to occur elsewhere in the limited range of 
the mountain yellow-legged frog.
    The Angeles and San Bernardino National Forests manage all known 
locations of mountain yellow-legged frogs in southern California. 
However, the FS does not include Rana muscosa on its list of sensitive 
species, although the Angeles and San Bernardino National Forests 
manage the frog as if it were sensitive (M. Rogers, in litt., 1997). 
Nevertheless, the FS does not have a management plan for the mountain 
yellow-legged frog or an adaptive management strategy that addresses 
the specific conservation and recovery needs of the species. As noted 
in the discussion of factors A through C above, the presence of 
introduced trout on FS lands is a serious threat, and, now that the DPS 
has been reduced to small isolated remnants, some other legal 
recreational activities occurring on FS lands may threaten the 
remaining frogs. The perilous status of the mountain yellow-legged frog 
reflects the overall failure or inability of existing CEQA, National 
Environmental Policy Act, and other Federal, State, and local 
ordinances and statutes to protect and provide for the conservation of 
this DPS.

E. Other Natural or Manmade Factors Affecting its Continued Existence

    Because the remaining populations of the DPS are small, isolated 
remnants, they are vulnerable to random natural events that could 
quickly eliminate them. It is a widely recognized principle that, in 
general, small populations are more vulnerable to extinction than large 
ones (Pimm 1991; Noss and Cooperrider 1994). Noss and Cooperrider 
(1994) identified four major factors that predispose small populations 
to extinction: (1) Environmental variation and natural catastrophes 
like unusually harsh weather, fires, or other unpredictable 
environmental phenomena; (2) chance variation in age and sex ratios or 
other population parameters (demographic stochastisity); (3) genetic 
deterioration resulting in inbreeding depression and genetic drift 
(random changes in gene frequencies); and (4) disruption of 
metapopulation dynamics (i.e., some species are distributed as systems 
of local populations linked by occasional dispersal, which wards off 
demographic or genetic deterioration).
    It is likely that some or a combination of these factors contribute 
to an increased probability of extinction of the remaining populations 
and the entire DPS. For example, Stewart (in litt., 1995) and Jennings 
(in litt., 1995) believe that flooding and fires could easily eliminate 
entire populations of mountain yellow-legged frogs, and Stewart (in 
litt., 1995) believes flooding during the winter of 1969 was the major 
factor in the loss of mountain yellow-legged frogs from Evey Canyon in 
the San Gabriel Mountains. An illustration of possible demographic 
effects is seen in the results of a limited survey by Jennings (1995), 
who found skewed sex ratios in the San Gabriel Mountains populations. 
If the results accurately reflect the real sex ratios in these 
populations, the effective population sizes are much lower than the 
census populations. When effective population size is small, the 
negative consequences can be demographic (e.g., not enough individuals 
of a given sex) or genetic (e.g., inbreeding depression), and can 
predispose these populations to a higher risk of extinction. The 
population genetics and metapopulation dynamics of the southern 
mountain yellow-legged frog have not been investigated, but we believe 
that the connectivity of populations within the DPS is substantially 
reduced compared to the recent past.
    Because the southern DPS consists of small, isolated populations, 
it is particularly vulnerable to some or all of the effects of chance 
listed above. Given the low probability of improving the status of the 
DPS under the status quo, the probability of small population size 
playing a role in the extinction of one or more local populations 
within the next few years is high. Any local extinctions will further 
isolate the remaining populations and probably reduce the time to 
extinction for the entire DPS.
    In summary, in southern California the mountain yellow-legged frog 
DPS is threatened by predation from introduced trout and possibly by 
other factors (e.g., airborne contaminants, pathogens) that are 
difficult to pinpoint and are currently the subject of national and 
worldwide investigations. Other local factors (recreational dredging, 
camping, day use), that would not cause appreciable harm if the DPS had 
not been reduced to small remnants, now represent serious actual or 
potential local threats. Compounding the effects of the large-scale 
(trout) and local (recreation) threats, the DPS has been reduced to 
very small isolated or semi-isolated populations that random events are 
now likely to contribute to local extinctions, which will reduce the 
time to extinction of the entire DPS. Even though we may never fully 
understand all the causes of decline, the available information 
suggests a high probability that this frog may be extinct in southern 
California within a few decades. We have carefully assessed the best 
scientific and commercial information available regarding the past, 
present, and future threats facing the DPS in determining to propose 
listing. Based on this evaluation, we propose to list the southern 
California DPS of mountain yellow-legged frog as endangered. We 
considered but did not select other alternatives to this action because 
not listing this DPS as endangered, or listing it as threatened, would 
not provide adequate protection and would not be in keeping with the 
purpose of the Act or the definitions therein. This DPS consists of 9 
small, relatively isolated

[[Page 71720]]

populations from which a combined total of fewer than 100 adults have 
been observed in recent surveys. Although all of the factors that have 
caused it to decline to this low level may never be known, the DPS is 
in immediate danger of extinction.

Critical Habitat

    Critical habitat is defined in section 3 of the Act as: (i) the 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the provisions of section 4 of 
the Act, on which are found those physical or biological features (I) 
essential to the conservation of the species and (II) that may require 
special management considerations or protection, and (ii) specific 
areas outside the geographical area occupied by a species at the time 
it is listed, upon a determination by the Secretary that such areas are 
essential for the conservation of the species (16 U.S.C. 1532(5)). 
``Conservation'' means the use of all methods and procedures needed to 
bring an endangered or threatened species to the point at which 
protection under the Act is no longer necessary.
    Due to the small number of populations, the mountain yellow-legged 
frog is vulnerable to unrestricted collection, vandalism, or other 
disturbance. We are concerned that these threats might be exacerbated 
by the publication of critical habitat maps and further dissemination 
of locational information. However, we have examined the evidence 
available for the mountain yellow-legged frog and have not found 
significant specific evidence of taking, vandalism, collection, or 
trade of this species or any similarly situated species. Consequently, 
consistent with applicable regulations (50 CFR 424.12(a)(1)(i)) and 
recent case law, we do not expect that the identification of critical 
habitat will increase the degree of threat to this species of taking or 
other human activity.
    In the absence of a finding that critical habitat would increase 
threats to a species, if there are any benefits to critical habitat 
designation, then a prudent finding is warranted. In the case of this 
species, there may be some benefits to designation of critical habitat. 
The primary regulatory effect of critical habitat is the section 7 
requirement that Federal agencies refrain from taking any action that 
destroys or adversely modifies critical habitat. While a critical 
habitat designation for habitat currently occupied by this species 
would not be likely to change the section 7 consultation outcome 
because an action that destroys or adversely modifies such critical 
habitat would also be likely to result in jeopardy to the species, 
there may be instances where section 7 consultation would be triggered 
only if critical habitat is designated. Examples could include 
unoccupied habitat or occupied habitat that may become unoccupied in 
the future. There may also be some educational or informational 
benefits to designating critical habitat. Therefore, we find that 
critical habitat is prudent for this DPS of the mountain yellow-legged 
    The Final Listing Priority Guidance for FY 2000 (64 FR 57114) 
states, ``The processing of critical habitat determinations (prudency 
and determinability decisions) and proposed or final designations of 
critical habitat will be funded separately from other section 4 listing 
actions and will no longer be subject to prioritization under the 
Listing Priority Guidance. Critical habitat determinations, which were 
previously included in final listing rules published in the Federal 
Register, may now be processed separately, in which case stand-alone 
critical habitat determinations will be published as notices in the 
Federal Register. We will undertake critical habitat determinations and 
designations during FY 2000 as allowed by our funding allocation for 
that year.'' As explained in detail in the Listing Priority Guidance, 
our listing budget is currently insufficient to allow us to immediately 
complete all of the listing actions required by the Act. Deferral of 
the critical habitat designation for this DPS of the mountain yellow-
legged frog will allow us to concentrate our limited resources on 
higher priority critical habitat and other listing actions, while 
allowing us to put in place protections needed for the conservation of 
the mountain yellow-legged frog without further delay.
    We plan to employ a priority system for deciding which outstanding 
critical habitat designations should be addressed first. We will focus 
our efforts on those designations that will provide the most 
conservation benefit, taking into consideration the efficacy of 
critical habitat designation in addressing the threats to the species, 
and the magnitude and immediacy of those threats. We will develop a 
proposal to designate critical habitat for this DPS of the mountain 
yellow-legged frog as soon as feasible, considering our workload 

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include requirements for Federal protection, 
prohibitions against certain practices, and recovery actions. The Act 
provides for possible land acquisition/exchange and cooperation with 
the States. The protection required of Federal agencies and the 
prohibitions against certain activities involving listed species are 
discussed, in part, below. Listing of the southern California DPS as 
endangered will provide for the development of a recovery plan. Such a 
plan will bring together both State and Federal efforts for the 
mountain yellow-legged frog's conservation. The plan will establish a 
framework for cooperation and coordination among agencies in 
conservation efforts. The plan will set recovery priorities and 
estimate costs of various tasks necessary to accomplish them. It will 
also describe site-specific management actions necessary to achieve 
conservation and survival of the southern California DPS of the 
mountain yellow-legged frog.
    Section 7(a) of the Act, as amended, requires Federal agencies to 
evaluate their actions with respect to any species that is proposed or 
listed as endangered or threatened and with respect to its critical 
habitat, if any is being designated. Regulations implementing this 
interagency cooperation provision of the Act are codified at 50 CFR 
part 402. Section 7(a)(4) requires Federal agencies to confer 
informally with the Service on any action that is likely to jeopardize 
the continued existence of a proposed species or result in destruction 
or adverse modification of its proposed critical habitat. If a species 
is listed subsequently, Section 7(a)(2) requires Federal agencies to 
ensure that activities they authorize, fund, or carry out are not 
likely to jeopardize the continued existence of such a species or to 
destroy or adversely modify its critical habitat. If a Federal action 
may affect a listed species or its critical habitat, the responsible 
Federal agency must enter into formal consultation with the Service.
    Federal agencies expected to have involvement with section 7 
regarding the southern California DPS of mountain yellow-legged frog 
include the U.S. Forest Service through its management activities and 
the U.S. Army Corps of Engineers through its permit authority under 
section 404 of the Clean Water Act. These agencies either administer 
lands containing the DPS or authorize, fund, or otherwise conduct 
activities that may affect the DPS.
    The Act and implementing regulations found at 50 CFR 17.21 set 
forth a series of general prohibitions and exceptions that apply to all 
endangered wildlife. These prohibitions, in part,

[[Page 71721]]

make it illegal for any person subject to the jurisdiction of the 
United States to take (including harass, harm, pursue, hunt, shoot, 
wound, kill, trap, capture, collect, or attempt any such conduct), 
import or export, transport in interstate or foreign commerce in the 
course of commercial activity, or sell or offer for sale in interstate 
or foreign commerce any listed species. It is also illegal to possess, 
sell, deliver, carry, transport, or ship any such wildlife that has 
been taken illegally. Certain exceptions apply to agents of the Service 
and State conservation agencies.
    It is the policy of the Service published in the Federal Register 
on July 1, 1994 (59 FR 34272), to identify to the maximum extent 
practical at the time a species is listed those activities that would 
or would not constitute a violation of section 9 of the Act. The intent 
of this policy is to increase public awareness of the effect of a 
listing on proposed and ongoing activities within a species' range. If 
the DPS is eventually listed, we believe the following actions would 
not be likely to result in a violation of section 9:
    Possession, delivery, or movement, including interstate transport 
and import into or export from the United States, involving no 
commercial activity, of dead specimens of this taxa that were collected 
prior to the date of publication in the Federal Register of the final 
regulation adding this taxa to the list of endangered species.
    Activities that the Service believes could potentially harm the 
southern California DPS of mountain yellow-legged frog and result in a 
violation of section 9 of the Act include, but are not limited to:
    (1) Take of southern California mountain yellow-legged frogs 
without a permit, which includes harassing, harming, pursuing, hunting, 
shooting, wounding, killing, trapping, capturing, or collecting, or 
attempting any of these actions;
    (2) Possessing, selling, delivering, carrying, transporting, or 
shipping illegally taken mountain yellow-legged frogs;
    (3) Interstate and foreign commerce (commerce across State and 
international boundaries) and import/export (as discussed earlier in 
this section);
    (4) Introduction of nonnative species that compete or hybridize 
with, or prey on, mountain yellow-legged frogs; and
    (5) Destruction or alteration of mountain yellow-legged frog 
habitat by dredging, channelization, diversion, in-stream vehicle 
operation or rock removal, or other activities that result in the 
destruction or significant degradation of cover, channel stability, 
substrate composition, temperature, and habitat used by the species for 
foraging, cover, migration, and breeding; and
    (6) Discharges or dumping of toxic chemicals, silt, or other 
pollutants into waters supporting mountain yellow-legged frogs by 
mining, or other developmental or land management activities that 
result in destruction or significant degradation of cover, channel 
stability, substrate composition, temperature, and habitat used by the 
species for foraging, cover, migration, and breeding.
    Questions regarding whether specific activities may constitute a 
violation of section 9 should be directed to the Field Supervisor of 
our Carlsbad Fish and Wildlife Office (see ADDRESSES section). Requests 
for copies of the regulations and inquiries regarding them may be 
addressed to the U.S. Fish and Wildlife Service, Ecological Services, 
Endangered Species Permits, 911 Northeast 11th Avenue, Portland, Oregon 
97232-4181 (503/231-6241; FAX 503/231-6243).
    Permits may be issued to carry out otherwise prohibited activities 
involving endangered wildlife species under certain circumstances. 
Regulations governing these permits are at 50 CFR 17.22 and 17.23. Such 
permits are available for scientific purposes, to enhance the 
propagation or survival of the species, for incidental take in 
connection with otherwise lawful activities, and/or for economic 

Public Comments Solicited

    The Service intends that any final action resulting from this 
proposal will be as accurate and as effective as possible. Therefore, 
comments or suggestions from the public, other concerned governmental 
agencies, the scientific community, industry, or any other interested 
party concerning this proposed rule are hereby solicited. Comments 
particularly are sought concerning:
    (1) Biological, commercial trade, or other relevant data concerning 
any threat (or lack thereof) to this species;
    (2) The distribution of resident rainbow trout in the mountains of 
southern California prior to the stocking programs of the California 
Department of Fish and Game;
    (3) The location of any additional occurrences of this species and 
the reasons why any habitat should or should not be determined to be 
critical habitat as provided by section 4 of the Act;
    (4) Additional information concerning the range, distribution, and 
population size of this species; and
    (5) Current or planned activities in the subject area and their 
possible impacts on the southern California population of mountain 
yellow-legged frogs.
    Final promulgation of the regulation(s) on this species will take 
into consideration the comments and any additional information received 
by the Service. Such communications may lead to a final regulation that 
differs from this proposal.
    The Endangered Species Act provides for one or more public hearings 
on this proposal, if requested. Requests must be received within 45 
days of the date of publication of the proposal in the Federal 
Register. Such requests must be made in writing and addressed to 
Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife 
Office (see ADDRESSES section).

National Environmental Policy Act

    The U.S. Fish and Wildlife Service has determined that 
environmental assessments and environmental impact statements, as 
defined under the authority of the National Environmental Policy Act of 
1969, need not be prepared in connection with regulations adopted 
pursuant to section 4(a) of the Endangered Species Act of 1973, as 
amended. A notice outlining the Service's reasons for this 
determination was published in the Federal Register on October 25, 1983 
(48 FR 49244).

References Cited

    A complete list of all references cited herein are available upon 
request from the Carlsbad Field Office (see ADDRESSES above).


    The primary author of this document is Paul J. Barrett, Carlsbad 
Fish and Wildlife Office (see ADDRESSES section).

List of Subjects in 50 CFR Part 17

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

Proposed Regulation Promulgation

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


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

    Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C. 
4201-4245; Pub. L. 99-625, 100 Stat. 3500, unless otherwise noted.

[[Page 71722]]

    2. Section 17.11(h) is amended by adding the following, in 
alphabetical order under AMPHIBIANS, to the List of Endangered and 
Threatened Wildlife to read as follows:

Sec. 17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

                        Species                                                    Vertebrate
--------------------------------------------------------                        population where                                  Critical     Special
                                                            Historic range       endangered or         Status      When listed    habitat       rules
           Common name                Scientific name                              threatened

                   *                  *                  *                  *                  *                  *                  *

                   *                  *                  *                  *                  *                  *                  *
Frog, mountain yellow-legged.....  Rana muscosa........  U.S.A. (California,  U.S.A., southern     E               ...........           NA           NA
                                                          Nevada) including    California.
                                                          San Diego, Orange,
                                                          Riverside, San
                                                          Bernardino, and
                                                          Los Angeles

                   *                  *                  *                  *                  *                  *                  *

    Dated: December 10, 1999.
Jamie Rappaport Clark,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 99-33087 Filed 12-17-99; 11:48 am]