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

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AF83

Endangered and Threatened Wildlife and Plants: Proposed

Endangered Status for the Southern California Distinct Vertebrate

Population Segment of the Mountain Yellow-Legged Frog

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the Fish and Wildlife Service (Service), propose to list

the southern California distinct vertebrate population segment (DPS) of

mountain yellow-legged frog (Rana muscosa) as endangered, pursuant to

the Endangered Species Act of 1973, as amended (Act). In southern

California, this DPS has been reduced to only a few isolated remnants

in the San Gabriel, San Jacinto, and San Bernardino Mountains.

Hypothesized causes of the decline include predation from introduced

trout or possibly some other widespread environmental effects such as

airborne contaminants. These effects have probably acted in combination

to produce the decline. The chronology of the decline is not well

documented, but it appears that a precipitous decline occurred over the

last three or four decades. The decline went largely unnoticed and was

not studied. In addition to predation from trout and other widespread

factors, the few remaining frogs are now threatened by recreational

suction dredging for gold and human activities at campgrounds and day

use areas. The remnant populations are so small that they are now at

risk from random genetic, demographic, and environmental effects as

well. This proposed rule constitutes the 12-month finding on a petition

to list the southern California population of mountain yellow-legged

frog as threatened or endangered. This proposed rule, if made final,

would implement the Federal protection and recovery provisions afforded

by the Act for this DPS. We welcome data and comment from the public on

this proposal.

DATES: You must submit any comments by February 22, 2000 and public

hearing requests by February 7, 2000.

ADDRESSES: You may send comments and materials concerning this proposal

to the Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish

and Wildlife Office, 2730 Loker Avenue West, Carlsbad, California

92008. You may inspect comments and materials received, by appointment,

during normal business hours at the above address.

FOR FURTHER INFORMATION CONTACT: Ken Berg at the above address

(telephone 760/431-9440).

SUPPLEMENTARY INFORMATION:

Background

The mountain yellow-legged frog is a true frog in the family

Ranidae. Mountain yellow-legged frogs were originally described by Camp

in 1917 (as cited by Zweifel 1955) as a subspecies of Rana boylii.

Zweifel (1955) demonstrated that frogs from the high Sierra and the

mountains of southern California were somewhat similar to each other

yet were distinct from the rest of the R. boylii (=boylei) group. Since

that time, most authors have followed Zweifel, treating the mountain

yellow-legged frog as a full species, Rana muscosa.

Mountain yellow-legged frogs are moderately sized, about 40 to 80

millimeters (mm) (1.5 to 3 inches (in)) from snout to urostyle (the

pointed bone at the base of the backbone) (Jennings and Hayes 1994;

Zweifel 1955). The pattern is variable, ranging from discrete dark

spots that can be few and large, to smaller and more numerous spots

with a mixture of sizes and shapes, to irregular lichen-like patches or

a poorly defined network (Zweifel 1955). The body color is also

variable, usually a mix of brown and yellow, but often with gray, red,

or green-brown. Some individuals may be dark brown with little pattern

(Jennings and Hayes 1994). The back half of the upper lip is pale.

Folds are present on each side of the back, but usually they are not

prominent (Stebbins 1985). The throat is white or yellow, sometimes

with mottling of dark pigment (Zweifel 1955). The belly and

undersurface of the high limbs are yellow, which ranges in hue from

pale lemon yellow to an intense sun yellow. The iris is gold with a

horizontal, black counter shading stripe (Jennings and Hayes 1994).

In the Sierra Nevada Mountains of California, the mountain yellow-

legged frog ranges from southern Plumas County to southern Tulare

County (Jennings and Hayes 1994), at elevations

[[Page 71715]]

mostly above 1,820 meters (m) (6,000 feet (ft)). The frogs of the

Sierra Nevada are isolated from the frogs of the mountains of southern

California by the Tehachapi Mountains and a distance of about 225

kilometers (km) (140 miles (mi)). The southern California frogs now

occupy portions of the San Gabriel, San Bernardino, and San Jacinto

Mountains. Zweifel (1955) noted the presence of an isolated southern

population on Mt. Palomar in northern San Diego County, but this

population appears to be extinct (Jennings and Hayes 1994). In southern

California, the elevation range reported by Stebbins (1985) is 182 m

(600 ft) to 2,273 m (7,500 ft). Representative localities, including

some that are no longer occupied, which demonstrate the wide elevation

range that mountain yellow-legged frogs inhabited in southern

California, include Eaton Canyon, Los Angeles County (370 m (1,220 ft))

and Bluff Lake, San Bernardino County (2,290 m (7,560 ft)). The

southern California locations now occupied by mountain yellow-legged

frogs range from City Creek, in the San Bernardino Mountains (760 m

(2,500 ft)), to Dark Canyon in the San Jacinto Mountains (1,820 m

(6,000 ft)).

Southern California mountain yellow-legged frogs are diurnal,

highly aquatic frogs, occupying rocky and shaded streams with cool

waters originating from springs and snowmelt. In these areas, juveniles

and adults feed on small, streamside arthropods (Jennings and Hayes

1994). They do not occur in the smallest creeks. The coldest winter

months are spent in hibernation, probably under water or in crevices in

the bank. Mountain yellow-legged frogs emerge from overwintering sites

in early spring, and breeding soon follows. Eggs are deposited in

shallow water where the egg mass is attached to vegetation or the

substrate. In the Sierra Nevada, larvae select warm microhabitats

(Bradford 1984 cited in Jennings and Hayes 1994), and the time to

develop from fertilization to metamorphosis reportedly varies from 1 to

2.5 years (Jennings and Hayes 1994).

Prior to the late 1960s, mountain yellow-legged frogs were abundant

in many southern California streams (G. Stewart, in litt. 1995), but

they now appear to be absent from most places in which they previously

occurred. Jennings and Hayes (1994) believe that mountain yellow-legged

frogs are now absent from more than 99 percent of their previous range

in southern California. This decline is part of a well-known larger

pattern of declines among native ranid frogs in the western United

States (Hayes and Jennings 1986; Drost and Fellers 1996). Some of the

western ranid frog species experiencing noticeable declines are the

California red-legged frog (Rana aurora draytonii) (61 FR 25813), the

spotted frog (R. pretiosa and R. luteventris), the Cascades frog (R.

cascadae), and the Chiricahua leopard frog (R. chiricauhensis) (62 FR

49398). Nowhere have the declines been any more pronounced than in

southern California, where, besides declines in mountain yellow-legged

frogs, the California red-legged frog has been reduced to a few small

remnants (61 FR 25813), and the foothill yellow-legged frog (R. boylii)

may be extinct (Jennings and Hayes 1994.)

The mechanisms causing the declines of western frogs are not well

understood and are certain to vary somewhat among species, but the two

most common and well-supported hypotheses for widespread declines of

western ranid frogs are: (1) Past habitat destruction related to

unregulated activities such as logging and mining and more recent

habitat conversions for water development, irrigated agriculture, and

commercial development (Hayes and Jennings 1986; 61 FR 25813); and (2)

alien predators and competitors (Bradford 1989; Knapp 1996; Kupferberg

1997). Natural populations may be killed off directly by these factors

operating alone or in combination, or these factors so severely disrupt

the normal population dynamics that when local extinctions occur,

regardless of the cause, natural recolonization is impossible. Other

environmental factors that could have adverse effects over a wide

geographic range include pesticides, certain pathogens, and

ultraviolet-B (beyond the visible spectrum) radiation, but their role,

if any, in amphibian declines is not well understood (Reaser 1996).

These factors, acting singly or in combination, may be contributing to

widespread, systematic declines of western ranid frogs. Determining

their effects, however, is not an easy task (Reaser 1996; Wake 1998),

and the Department of the Interior (USDOI) currently supports an

initiative to fund research on the causes of amphibian declines (see

examples in USDOI 1998).

Some of the same factors that are hypothesized to have caused

declines of other western ranid frogs are likely to be responsible for

the reduction of the mountain yellow-legged frog in southern

California. Because the declines have been so precipitous, and have

spared only a small number of frogs in a few localities, the factors,

and their interactions, that caused the decline may never be fully

understood. We believe that these factors are still operating, and

unless reversed, a high probability exists that this frog may be

extinct in southern California within a few decades. In the case of the

mountain yellow-legged frog, the only factor listed above that we

believe can be ruled out as a likely cause of decline is habitat

destruction related to activities such as logging, mining, irrigated

agriculture, and commercial development. The range of the mountain

yellow-legged frog in southern California is mainly on public land

administered by the U.S. Forest Service (FS). Most of the rugged

canyons and surrounding mountainous terrain have been altered little

and look much the same today as they did when earlier naturalists such

as Lawrence Klauber collected mountain yellow-legged frogs there in the

early decades of the 1900s.

Current Range and Status

In southern California, mountain yellow-legged frogs can still be

found in four small streams in the San Gabriel Mountains, the upper

reaches of the San Jacinto River system in the San Jacinto Mountains,

and at a single locality on City Creek, a tributary of the Santa Ana

River, in the San Bernardino Mountains (Jennings and Hayes 1994; M. D.

Wilcox in litt., 1998). These areas along with the numbers of frogs

most recently observed in each area are described below.

San Gabriel Mountains: Surveys conducted from 1993 to 1997 revealed

small isolated populations in the upper reaches of Prairie Creek/

Vincent Gulch, Devil's Canyon, and Alder Creek/East Fork, on the East

Fork of the San Gabriel River, and Little Rock Creek on the Mojave

River (Jennings and Hayes 1994 and references therein; Jennings 1995;

Jennings 1998). The surveys involved one to three field biologists and

were conducted over 1-5 days per site. Over the course of these field

studies, 15 adults or fewer were observed at any 1 site, and, after the

1995 season, Jennings (1995) concluded that the actual population at

each of the sites was only 10-20 adults.

San Jacinto Mountains: Small populations of mountain yellow-legged

frogs also occur in four tributaries in the upper reaches of the North

Fork, San Jacinto River on Mount San Jacinto: Dark Canyon, Hall Canyon,

Fuller Mill Creek, and the main North Fork, San Jacinto River (Jennings

and Hayes 1994; Jennings 1995; Jennings 1998). The number of frogs

occupying these sites is not known, but fewer than 10 adult frogs per

site per year have been observed in surveys from 1995 to the present.

San Bernardino Mountains: A few tadpoles and 26 recently

transformed

[[Page 71716]]

juveniles, but no adults, were rediscovered on a roughly 1-mile reach

of the East Fork, City Creek during the summer of 1998 (M. D. Wilcox in

litt., 1998). Previous to this finding, mountain yellow-legged frogs

had not been observed in the San Bernardino Mountains since the 1970s

(Jennings and Hayes 1994), even though surveys were conducted during

the summer and fall of 1997 and 1998 (Holland 1997; Tierra Madre 1999).

When frogs were encountered during field surveys accomplished

between 1988 and 1995, only a few individuals were observed. Jennings

and Hayes (1994) and Jennings (1995) suggested that the entire

population of mountain yellow-legged frogs in the San Gabriel and San

Jacinto Mountains (8 more or less isolated sites) was probably fewer

than 100 adult frogs. Their rough estimate is based on a compilation of

the results of visual surveys generally conducted on a single day, not

on formal population abundance estimation techniques. While the precise

number of adult frogs may be greater than 100, we concur with Jennings

and Hayes (1994) that, in the San Gabriel and San Jacinto Mountains,

the available data indicate that this once widespread species is now

found in only a small number of relatively isolated populations. We do

not know the population size of adult frogs at the recently

rediscovered site on the east fork of City Creek in the San Bernardino

Mountains, but because no adults and only a few juveniles and tadpoles

were encountered, the adult population is probably small. Thus, we

conclude that each of the three mountain ranges (San Gabriel, San

Jacinto, San Bernardino) contains a small number of small, relatively

isolated populations.

Distinct Vertebrate Population Segment

We analyzed the mountain yellow-legged frog according to the joint

Service and National Marine Fisheries Service Policy Regarding the

Recognition of Distinct Vertebrate Populations, published in the

Federal Register on February 7, 1996 (61 FR 4722). We consider three

elements in determining whether a vertebrate population segment could

be treated as threatened or endangered under the Act: discreteness,

significance, and conservation status in relation to the standards for

listing. Discreteness refers to the isolation of a population from

other members of the species and is based on two criteria: (1) Marked

separation from other populations of the same taxon resulting from

physical, physiological, ecological, or behavioral factors, including

genetic discontinuity, or (2) populations delimited by international

boundaries. We determine significance either by the importance or

contribution, or both, of a discrete population to the species

throughout its range. Our policy lists four examples of factors that

may be used to determine significance: (1) Persistence of the discrete

population segment in an ecological setting unusual or unique for the

taxon; (2) evidence that loss of the discrete population segment would

result in a significant gap in the range of the taxon; (3) evidence

that the discrete population segment represents the only surviving

natural occurrence of the taxon that may be more abundant elsewhere as

an introduced population outside its historic range; and (4) evidence

that the discrete population segment differs markedly from other

populations of the taxon in its genetic characteristics. If we

determine that a population segment is discrete and significant, we

evaluate it for endangered or threatened status based on the Act's

standards.

Discreteness: The range of the mountain yellow-legged frog is

divided by a natural geographic barrier, the Tehachapi Mountains, which

isolate Sierran frogs from those in the mountains of southern

California. The distance of the separation is about 225 km (140 mi),

but the separation may not have been this great in the recent past

because a frog collected in 1952 on Breckenridge Mountain in Kern

County was identified by Jennings and Hayes (1994) as a mountain

yellow-legged frog. The geographic separation of the Sierran and

southern California frogs was recognized in the earliest description of

the species by Camp (1917, cited in Zweifel 1955), who treated frogs

from the two localities as separate subspecies within the R. boylii

group. He designated the Sierran frogs R. b. sierrae and the southern

California frogs R. b. muscosa, based on geography and subtle

morphological differences. Zweifel (1955) reevaluated the morphological

evidence and found it insufficient to warrant Camp's recognition of two

subspecies, the chief difference between the two being hind-limb

length.

More recently, Ziesmer (1997) analyzed the calls of Sierran (Alpine

and Mariposa Counties) and southern California (San Jacinto Mountains

and Riverside County) mountain yellow-legged frogs. He found that the

calls of Sierran frogs differed from southern California frogs in pulse

rate, harmonic structure, and dominant frequency. Based on a limited

sample, Ziesmer concluded that the results supported the hypothesis

that mountain yellow-legged frogs from the Sierra Nevada and southern

California are separate species.

Allozyme (a form of an enzyme produced by a gene) variation

throughout the range of the mountain yellow-legged frog has been

examined, but the results are open to interpretation (Jennings and

Hayes 1994 and references therein). In the work most applicable to the

question of the distinctiveness of the Sierran and southern California

frogs, David Green (pers. comm., 1998) analyzed allozyme variation in

central Sierran mountain yellow-legged frogs (four individuals,

Tuolumne County) and southern California mountain yellow-legged frogs

(two individuals, Riverside County). He found fixed differences at 6 of

28 loci (sites on a chromosome occupied by specific genes). These

limited, unpublished data suggest that Sierran and southern California

mountain yellow-legged frogs are different at a level that could

support the recognition of full species. However, because of the small

number of individuals per sample and the limited number of samples, we

view these results cautiously. It is possible that existing variation

at those six loci may not have been detected with such a small number

of individuals sampled. To better understand whether a genetic

discontinuity significant enough to warrant full species rank exists

between Sierran frogs and those from the mountains of southern

California, samples of frogs from the southern Sierra Nevada,

especially the Greenhorn Mountains, would be of particular interest.

Although Green's limited allozyme analysis may not be sufficient to

support recognizing the Sierran and southern California populations as

separate species, it does support the conclusion of significant

geographic separation. This conclusion is also supported by earlier

observations of morphological differences (Zweifel 1955, and references

therein) and differences in vocalizations (Ziesmer 1997). Considered

together, the evidence supports an interpretation of isolation between

the two populations of frogs over a very long period. We find that the

southern California frogs meet the criterion of ``marked separation

from other populations of the same taxon'' and qualify as discrete

according to the Policy Regarding the Recognition of Distinct

Vertebrate Populations (61 FR 4722).

Significance: One of the most striking differences between Sierran

and southern California mountain yellow-legged frogs is the habitats

they occupy. Zweifel (1955) observed that the frogs in southern

California are typically found

[[Page 71717]]

in steep gradient streams in the chaparral belt, even though they may

range up into small meadow streams at higher elevations. In contrast,

Sierran frogs are most abundant in high elevation lakes and slow-moving

portions of streams. Bradford's (1989) southern Sierra Nevada study

site, for example, was in Sequoia and Kings Canyon National Parks at

high elevations (between 2,910-3,430 m (9,600-11,319 ft)). The rugged

canyons of the arid mountain ranges of southern California bear little

resemblance to the alpine lakes of the Sierra Nevada. On the basis of

habitat alone, one might easily conclude that these are two very

different frogs.

The mountain yellow-legged frogs of southern California comprise

the southern portion of the species' range. The extinction of this

southern group would be significant because it would substantially

reduce the overall range as it is currently understood, and what is now

a gap in the distribution, the Tehachapi Mountains, would become the

southern limit of the species' range.

In addition, evidence exists that the mountain yellow-legged frog

is not simply a single species with a disjunct distribution (cited in

Zweifel 1955; Stebbins 1985). As discussed above, vocal and genetic

differences exist between Sierran and southern California mountain

yellow-legged frogs. Although the data are limited and some important

variation may have been missed, they are consistent with the earlier

interpretation by Camp (1917 cited in Zweifel 1955) and numerous other

authors prior to Zweifel (e.g., Stebbins 1954) who treated the two

forms as taxonomically distinct. If the differences in vocalization

described by Ziesmer (1997) and the allozyme variation described by

Green (per. comm., 1998) accurately characterize differences between

the two forms, then the Sierran and southern California frogs are quite

different and have been isolated for a very long time.

Our conclusion that Sierran and southern California frogs are very

different from each other, and may even merit recognition as separate

subspecies or possibly even species, is based on the cumulative weight

of the available evidence. We find that the mountain yellow-legged

frogs inhabiting the mountains of southern California meet the

significance criteria under our Policy Regarding the Recognition of

Distinct Vertebrate Populations (61 FR 4722) on the basis of the

geographical, ecological, vocal, and genetic discontinuities described

above.

In the remainder of this proposed rule, we evaluate the southern

California mountain yellow-legged frog for endangered status based on

the Act's standards. For clarity, we refer to all mountain yellow-

legged frogs south of the Tehachapi Mountains as the southern

California DPS. We use the word ``population'' to describe all of the

frogs living in a particular place.

Previous Federal Action

On July 13, 1995, we received a petition dated July 10, 1995, from

D.C. ``Jasper'' Carlton (of the Biodiversity Legal Foundation), Bonnie

M. Dombrowski, and Michael C. Long to list as threatened or endangered

the southern California populations of the mountain yellow-legged frog

(Rana muscosa) pursuant to the Act. Accompanying the petition was

supporting information related to the taxonomy, ecology, and the past

and present distribution of the species. We reviewed the petition,

supporting documentation, and other information cited in this proposed

rule to determine if substantial information was available to indicate

that the requested action may be warranted. On July 8, 1997, we

published a 90-day finding for the petition to list the southern

California populations of the mountain yellow-legged frog (62 FR

36481). We found the southern California population to be a DPS and

furthermore found the petition presented substantial information

indicating the listing of the species (DPS) may be warranted. Once we

made the finding that the petition presented substantial information,

we commenced a status review pursuant to section 4(b)(3)(A) of the Act.

However, consistent with the applicable Listing Priority Guidances (62

FR 55268; 63 FR 25502), our Carlsbad Field Office completed work on

higher priority listing actions before completing this 12-month finding

and proposed rule to list this DPS of the mountain yellow-legged frog.

The processing of this proposed rule conforms with our Listing

Priority Guidance published in the Federal Register on October 22, 1999

(64 FR 57114). The guidance clarifies the order in which we will

process rulemakings. Highest priority is processing emergency listing

rules for any species determined to face a significant and imminent

risk to its well-being (Priority 1). Second priority (Priority 2) is

processing final determinations on proposed additions to the lists of

endangered and threatened wildlife and plants. Third priority is

processing new proposals to add species to the lists. The processing of

administrative petition findings (petitions filed under section 4 of

the Act) is the fourth priority. The processing of critical habitat

determinations (prudency and determinability decisions) and proposed or

final designations of critical habitat will be funded separately from

other section 4 listing actions and will no longer be subject to

prioritization under the Listing Priority Guidance. The processing of

this proposed rule is a Priority 3 action.

Summary of Factors Affecting the Species

Section 4 of the Endangered Species Act (16 U.S.C. 1531 et seq.)

and the regulations (50 CFR part 424) that implement the listing

provisions of the Act set forth the procedures for adding species to

the Federal lists. A species may be determined to be an endangered or

threatened species due to one or more of the five factors described in

section 4(a)(1). These factors and their application to the southern

California DPS of mountain yellow-legged frogs are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment

of its Habitat or Range.

All nine known populations of southern California Rana muscosa

occur on lands owned and managed by the FS and are clustered within

three drainages, one in the San Gabriel Mountains, one in the San

Bernardino Mountains, and another on Mount San Jacinto. As such, the

habitats in which they live are protected against wholesale conversions

to other uses. However, with so few populations remaining, and with

each of those numbering only a few individuals, localized habitat

alterations, which would not be appreciable if the DPS were more wide-

ranging and abundant, threaten the DPS. Local habitat changes caused by

recreational suction dredging for gold and human use around

campgrounds, picnic grounds, and heavily used trails may harm the

habitat and contribute to local extinctions wherever these activities

intersect with mountain yellow-legged frogs.

Jennings (1995) observed suction dredging within the Wilderness

Area where mountain yellow-legged frogs occur on the East Fork, San

Gabriel River. He reported observing large quantities of trash and

toxic materials being dumped into the stream bed. If this practice is

continued, it could have harmful effects on the population inhabiting

the East Fork, San Gabriel River. The consequences for populations on

other San Gabriel River tributaries is difficult to predict, but any

losses would further isolate the remaining populations and probably

[[Page 71718]]

reduce the time to extinction for the DPS. Other than the East Fork,

San Gabriel River site, we do not know if recreational gold mining

occurs or at what level on or near sites occupied by frogs. Extensive

suction dredging activity at or near a breeding site could have the

harmful effect of killing eggs or larvae or changing the hydrology,

rendering it unsuitable for breeding. Some of the habitat effects of

suction dredging on streams are described by Harvey (1986), who found

dredging altered substrates and changed the habitat for fish and

invertebrates.

Fairly heavy camping and day use coincides with frog habitat along

the East Fork, San Gabriel River (dispersed camping), Prairie Fork

Creek (campground, recently burned and presently closed by the FS),

Little Rock Creek (trail, rock climbing), Dark Canyon (campground), and

Fuller Mill Creek (picnic ground). In areas occupied by frogs, human

presence in and along streams can disrupt the lives of eggs, larvae,

and adult frogs and change the entire character of the stream and its

bank and associated vegetation in ways that make whole sections of

stream less suitable for frogs. Only nine very small populations

remain, and at least four of these are in areas that receive reasonably

heavy human camping or day use. The loss of even small numbers of frogs

from any of these populations due to human camping or day use, either

alone or in combination with other factors, will increase the

probability of local extinction. Any local extinctions will further

isolate the remaining populations and probably reduce the time to

extinction for the DPS.

B. Overutilization for Commercial, Recreational, Scientific, or

Educational Purposes

Numerous museum specimens from many localities (Jennings and Hayes

1994) attest to the fact that, for decades, mountain yellow-legged

frogs from the southern DPS have been collected for scientific

purposes. These collections probably did not have an appreciable

effect. Now that the DPS has declined precipitously, populations are so

few in number, and the size of each population is so small, very little

or no scientific collecting of the southern DPS occurs. Collecting,

scientific or amateur, if it did occur, could seriously increase the

probability of extinction of any of the remaining populations. Any

local extinctions will further isolate the remaining populations and

probably reduce the time to extinction for the DPS.

C. Disease or Predation

Predation by introduced trout, including rainbow trout

(Oncorhynchus mykiss), is one of the best documented causes of the

decline of Sierran mountain yellow-legged frogs. Careful study of the

distributions of introduced trout and mountain yellow-legged frogs for

several years has shown conclusively that introduced trout have had

negative impacts on mountain yellow-legged frogs over much of the

Sierra Nevada (Bradford 1989; Knapp 1996). Bradford (1989) and Bradford

et al. (1993) concluded that introduced trout eliminate many

populations of mountain yellow-legged frogs and the presence of trout

in intervening streams sufficiently isolates other frog populations so

that recolonization after stochastic (random, naturally occurring)

local extinctions is essentially impossible. This mechanism is

sufficient to explain the elimination of Sierran mountain yellow-legged

frogs from the majority of sites they once inhabited, and, alone or in

combination with other factors, introduced trout have almost certainly

contributed to the widespread and systematic decline of the southern

DPS as well.

Virtually all streams in the mountains of southern California

contain populations of introduced rainbow trout, and trout are

routinely planted in Dark Canyon, Fuller Mill Creek in the San Jacinto

Mountains, and City Creek in the San Bernardino Mountains. Most of the

other streams still occupied by mountain yellow-legged frogs have

histories of trout introductions and probably contain naturally

reproducing, sustainable populations at, or very near, the sites

occupied by the frogs. Wherever the two species co-occur, trout are

likely to eliminate mountain yellow-legged frogs or keep populations

low and limit dispersal. The widespread occurrence of introduced trout

in the mountains of southern California may make it very difficult to

reverse the decline to extinction of the DPS.

Another introduced predator that could have effects on the DPS

similar to those of the trout, yet on a more limited scale, is the

bullfrog, Rana catesbeiana. Bullfrogs have been listed among the

threats to other western frogs (61 FR 25813; Kiesecker and Blaustein

1998) and toads (59 FR 64859). Bullfrogs are now widespread in southern

California and occur in many drainages formerly and currently occupied

by mountain yellow-legged frogs. The negative effects of bullfrogs on

mountain yellow-legged frogs in the mountains of southern California

are probably less widespread than those of introduced trout because

there is less overlap in their occurrence. Any habitat alterations that

are favorable to bullfrogs, however, will cause them to become abundant

locally. In areas where mountain yellow-legged frogs occur, this

increase could lead to local extinctions and increased isolation of the

remaining populations, which would probably reduce the time to

extinction for the entire DPS.

Bradford (1991) documented the loss of a Sierran population of Rana

muscosa due to the combined effect of ``red-leg'' disease (caused by

the bacterium Aeromonas hydrophila) and predation by Brewer's

blackbirds, Euphagus cyanocephalus. Another pathogen that is generating

concern among those who study amphibian declines is the chytrid fungus.

Chytrids may be seriously affecting amphibians in many places around

the world, and they have recently been discovered on larval mountain

yellow-legged frogs in the Sierra Nevada (Gary Fellers, pers. comm.

1999). Because of the small and isolated nature of the remaining

populations, disease could be serious. Any local extinctions caused by

disease would further isolate the remaining populations and probably

reduce the time to extinction for the entire DPS.

D. The Inadequacy of Existing Regulatory Mechanisms

Existing regulatory mechanisms have not stopped the decline of

mountain yellow-legged frogs in southern California. Existing

regulatory mechanisms that could provide some protection for the

mountain yellow-legged frog include: (1) Consideration under the

California Environmental Quality Act (CEQA); (2) consideration under

section 404 of the Clean Water Act (CWA); and (3) co-occurrence with

other species protected by the Endangered Species Act of 1973.

The State of California considers mountain yellow-legged frogs a

species of special concern, but it is not a threatened or endangered

species and receives no protection under the California Endangered

Species Act. California Sport Fishing Regulations include the mountain

yellow-legged frog as a protected species that may not be taken or

possessed at any time except under special permit from the California

Department of Fish and Game. This prohibition may help prevent threats

from collecting, but this threat is not a significant cause of the

decline, and the DPS is expected to continue declining toward

extinction even in the absence of collecting.

The CEQA requires a full public disclosure of the potential

environmental impact of proposed

[[Page 71719]]

projects. The public agency with primary authority or jurisdiction over

the project is designated as the lead agency and is responsible for

conducting a review of the project and consulting with other agencies

concerned with resources affected by the project. Section 15065 of the

CEQA guidelines require a finding of significance if a project has the

potential to ``reduce the number or restrict the range of a rare or

endangered plant or animal.'' Species that are eligible for listing as

rare, threatened, or endangered but are not so listed are given the

same protection as those species that are officially listed with the

State. Once significant impacts are identified, the lead agency has the

option to require mitigation for effects through changes in the project

or to decide that overriding considerations make mitigation infeasible.

In the latter case, projects may be approved that cause significant

environmental damage, such as destruction of endangered species.

Protection of listed species through CEQA is, therefore, at the

discretion of the lead agency involved. The CEQA provides that, when

overriding social and economic considerations can be demonstrated,

project proposals may go forward, even in cases where the continued

existence of the species may be threatened, or where adverse impacts

are not mitigated to the point of insignificance.

Besides the Act, the primary Federal law that potentially affords

some protection for the mountain yellow-legged frog is section 404 of

the CWA. The CWA may provide some general protections for species,

however, this DPS has declined precipitously under this Federal law.

The arroyo toad (Bufo microscaphus californicus), a federally

listed endangered species, is present in the San Gabriel Mountains, but

there is no benefit to the mountain yellow-legged frog because the two

species occupy different areas in the San Gabriel Mountains and the

arroyo toads are not known to occur elsewhere in the limited range of

the mountain yellow-legged frog.

The Angeles and San Bernardino National Forests manage all known

locations of mountain yellow-legged frogs in southern California.

However, the FS does not include Rana muscosa on its list of sensitive

species, although the Angeles and San Bernardino National Forests

manage the frog as if it were sensitive (M. Rogers, in litt., 1997).

Nevertheless, the FS does not have a management plan for the mountain

yellow-legged frog or an adaptive management strategy that addresses

the specific conservation and recovery needs of the species. As noted

in the discussion of factors A through C above, the presence of

introduced trout on FS lands is a serious threat, and, now that the DPS

has been reduced to small isolated remnants, some other legal

recreational activities occurring on FS lands may threaten the

remaining frogs. The perilous status of the mountain yellow-legged frog

reflects the overall failure or inability of existing CEQA, National

Environmental Policy Act, and other Federal, State, and local

ordinances and statutes to protect and provide for the conservation of

this DPS.

E. Other Natural or Manmade Factors Affecting its Continued Existence

Because the remaining populations of the DPS are small, isolated

remnants, they are vulnerable to random natural events that could

quickly eliminate them. It is a widely recognized principle that, in

general, small populations are more vulnerable to extinction than large

ones (Pimm 1991; Noss and Cooperrider 1994). Noss and Cooperrider

(1994) identified four major factors that predispose small populations

to extinction: (1) Environmental variation and natural catastrophes

like unusually harsh weather, fires, or other unpredictable

environmental phenomena; (2) chance variation in age and sex ratios or

other population parameters (demographic stochastisity); (3) genetic

deterioration resulting in inbreeding depression and genetic drift

(random changes in gene frequencies); and (4) disruption of

metapopulation dynamics (i.e., some species are distributed as systems

of local populations linked by occasional dispersal, which wards off

demographic or genetic deterioration).

It is likely that some or a combination of these factors contribute

to an increased probability of extinction of the remaining populations

and the entire DPS. For example, Stewart (in litt., 1995) and Jennings

(in litt., 1995) believe that flooding and fires could easily eliminate

entire populations of mountain yellow-legged frogs, and Stewart (in

litt., 1995) believes flooding during the winter of 1969 was the major

factor in the loss of mountain yellow-legged frogs from Evey Canyon in

the San Gabriel Mountains. An illustration of possible demographic

effects is seen in the results of a limited survey by Jennings (1995),

who found skewed sex ratios in the San Gabriel Mountains populations.

If the results accurately reflect the real sex ratios in these

populations, the effective population sizes are much lower than the

census populations. When effective population size is small, the

negative consequences can be demographic (e.g., not enough individuals

of a given sex) or genetic (e.g., inbreeding depression), and can

predispose these populations to a higher risk of extinction. The

population genetics and metapopulation dynamics of the southern

mountain yellow-legged frog have not been investigated, but we believe

that the connectivity of populations within the DPS is substantially

reduced compared to the recent past.

Because the southern DPS consists of small, isolated populations,

it is particularly vulnerable to some or all of the effects of chance

listed above. Given the low probability of improving the status of the

DPS under the status quo, the probability of small population size

playing a role in the extinction of one or more local populations

within the next few years is high. Any local extinctions will further

isolate the remaining populations and probably reduce the time to

extinction for the entire DPS.

In summary, in southern California the mountain yellow-legged frog

DPS is threatened by predation from introduced trout and possibly by

other factors (e.g., airborne contaminants, pathogens) that are

difficult to pinpoint and are currently the subject of national and

worldwide investigations. Other local factors (recreational dredging,

camping, day use), that would not cause appreciable harm if the DPS had

not been reduced to small remnants, now represent serious actual or

potential local threats. Compounding the effects of the large-scale

(trout) and local (recreation) threats, the DPS has been reduced to

very small isolated or semi-isolated populations that random events are

now likely to contribute to local extinctions, which will reduce the

time to extinction of the entire DPS. Even though we may never fully

understand all the causes of decline, the available information

suggests a high probability that this frog may be extinct in southern

California within a few decades. We have carefully assessed the best

scientific and commercial information available regarding the past,

present, and future threats facing the DPS in determining to propose

listing. Based on this evaluation, we propose to list the southern

California DPS of mountain yellow-legged frog as endangered. We

considered but did not select other alternatives to this action because

not listing this DPS as endangered, or listing it as threatened, would

not provide adequate protection and would not be in keeping with the

purpose of the Act or the definitions therein. This DPS consists of 9

small, relatively isolated

[[Page 71720]]

populations from which a combined total of fewer than 100 adults have

been observed in recent surveys. Although all of the factors that have

caused it to decline to this low level may never be known, the DPS is

in immediate danger of extinction.

Critical Habitat

Critical habitat is defined in section 3 of the Act as: (i) the

specific areas within the geographical area occupied by a species, at

the time it is listed in accordance with the provisions of section 4 of

the Act, on which are found those physical or biological features (I)

essential to the conservation of the species and (II) that may require

special management considerations or protection, and (ii) specific

areas outside the geographical area occupied by a species at the time

it is listed, upon a determination by the Secretary that such areas are

essential for the conservation of the species (16 U.S.C. 1532(5)).

``Conservation'' means the use of all methods and procedures needed to

bring an endangered or threatened species to the point at which

protection under the Act is no longer necessary.

Due to the small number of populations, the mountain yellow-legged

frog is vulnerable to unrestricted collection, vandalism, or other

disturbance. We are concerned that these threats might be exacerbated

by the publication of critical habitat maps and further dissemination

of locational information. However, we have examined the evidence

available for the mountain yellow-legged frog and have not found

significant specific evidence of taking, vandalism, collection, or

trade of this species or any similarly situated species. Consequently,

consistent with applicable regulations (50 CFR 424.12(a)(1)(i)) and

recent case law, we do not expect that the identification of critical

habitat will increase the degree of threat to this species of taking or

other human activity.

In the absence of a finding that critical habitat would increase

threats to a species, if there are any benefits to critical habitat

designation, then a prudent finding is warranted. In the case of this

species, there may be some benefits to designation of critical habitat.

The primary regulatory effect of critical habitat is the section 7

requirement that Federal agencies refrain from taking any action that

destroys or adversely modifies critical habitat. While a critical

habitat designation for habitat currently occupied by this species

would not be likely to change the section 7 consultation outcome

because an action that destroys or adversely modifies such critical

habitat would also be likely to result in jeopardy to the species,

there may be instances where section 7 consultation would be triggered

only if critical habitat is designated. Examples could include

unoccupied habitat or occupied habitat that may become unoccupied in

the future. There may also be some educational or informational

benefits to designating critical habitat. Therefore, we find that

critical habitat is prudent for this DPS of the mountain yellow-legged

frog.

The Final Listing Priority Guidance for FY 2000 (64 FR 57114)

states, ``The processing of critical habitat determinations (prudency

and determinability decisions) and proposed or final designations of

critical habitat will be funded separately from other section 4 listing

actions and will no longer be subject to prioritization under the

Listing Priority Guidance. Critical habitat determinations, which were

previously included in final listing rules published in the Federal

Register, may now be processed separately, in which case stand-alone

critical habitat determinations will be published as notices in the

Federal Register. We will undertake critical habitat determinations and

designations during FY 2000 as allowed by our funding allocation for

that year.'' As explained in detail in the Listing Priority Guidance,

our listing budget is currently insufficient to allow us to immediately

complete all of the listing actions required by the Act. Deferral of

the critical habitat designation for this DPS of the mountain yellow-

legged frog will allow us to concentrate our limited resources on

higher priority critical habitat and other listing actions, while

allowing us to put in place protections needed for the conservation of

the mountain yellow-legged frog without further delay.

We plan to employ a priority system for deciding which outstanding

critical habitat designations should be addressed first. We will focus

our efforts on those designations that will provide the most

conservation benefit, taking into consideration the efficacy of

critical habitat designation in addressing the threats to the species,

and the magnitude and immediacy of those threats. We will develop a

proposal to designate critical habitat for this DPS of the mountain

yellow-legged frog as soon as feasible, considering our workload

priorities.

Available Conservation Measures

Conservation measures provided to species listed as endangered or

threatened under the Act include requirements for Federal protection,

prohibitions against certain practices, and recovery actions. The Act

provides for possible land acquisition/exchange and cooperation with

the States. The protection required of Federal agencies and the

prohibitions against certain activities involving listed species are

discussed, in part, below. Listing of the southern California DPS as

endangered will provide for the development of a recovery plan. Such a

plan will bring together both State and Federal efforts for the

mountain yellow-legged frog's conservation. The plan will establish a

framework for cooperation and coordination among agencies in

conservation efforts. The plan will set recovery priorities and

estimate costs of various tasks necessary to accomplish them. It will

also describe site-specific management actions necessary to achieve

conservation and survival of the southern California DPS of the

mountain yellow-legged frog.

Section 7(a) of the Act, as amended, requires Federal agencies to

evaluate their actions with respect to any species that is proposed or

listed as endangered or threatened and with respect to its critical

habitat, if any is being designated. Regulations implementing this

interagency cooperation provision of the Act are codified at 50 CFR

part 402. Section 7(a)(4) requires Federal agencies to confer

informally with the Service on any action that is likely to jeopardize

the continued existence of a proposed species or result in destruction

or adverse modification of its proposed critical habitat. If a species

is listed subsequently, Section 7(a)(2) requires Federal agencies to

ensure that activities they authorize, fund, or carry out are not

likely to jeopardize the continued existence of such a species or to

destroy or adversely modify its critical habitat. If a Federal action

may affect a listed species or its critical habitat, the responsible

Federal agency must enter into formal consultation with the Service.

Federal agencies expected to have involvement with section 7

regarding the southern California DPS of mountain yellow-legged frog

include the U.S. Forest Service through its management activities and

the U.S. Army Corps of Engineers through its permit authority under

section 404 of the Clean Water Act. These agencies either administer

lands containing the DPS or authorize, fund, or otherwise conduct

activities that may affect the DPS.

The Act and implementing regulations found at 50 CFR 17.21 set

forth a series of general prohibitions and exceptions that apply to all

endangered wildlife. These prohibitions, in part,

[[Page 71721]]

make it illegal for any person subject to the jurisdiction of the

United States to take (including harass, harm, pursue, hunt, shoot,

wound, kill, trap, capture, collect, or attempt any such conduct),

import or export, transport in interstate or foreign commerce in the

course of commercial activity, or sell or offer for sale in interstate

or foreign commerce any listed species. It is also illegal to possess,

sell, deliver, carry, transport, or ship any such wildlife that has

been taken illegally. Certain exceptions apply to agents of the Service

and State conservation agencies.

It is the policy of the Service published in the Federal Register

on July 1, 1994 (59 FR 34272), to identify to the maximum extent

practical at the time a species is listed those activities that would

or would not constitute a violation of section 9 of the Act. The intent

of this policy is to increase public awareness of the effect of a

listing on proposed and ongoing activities within a species' range. If

the DPS is eventually listed, we believe the following actions would

not be likely to result in a violation of section 9:

Possession, delivery, or movement, including interstate transport

and import into or export from the United States, involving no

commercial activity, of dead specimens of this taxa that were collected

prior to the date of publication in the Federal Register of the final

regulation adding this taxa to the list of endangered species.

Activities that the Service believes could potentially harm the

southern California DPS of mountain yellow-legged frog and result in a

violation of section 9 of the Act include, but are not limited to:

(1) Take of southern California mountain yellow-legged frogs

without a permit, which includes harassing, harming, pursuing, hunting,

shooting, wounding, killing, trapping, capturing, or collecting, or

attempting any of these actions;

(2) Possessing, selling, delivering, carrying, transporting, or

shipping illegally taken mountain yellow-legged frogs;

(3) Interstate and foreign commerce (commerce across State and

international boundaries) and import/export (as discussed earlier in

this section);

(4) Introduction of nonnative species that compete or hybridize

with, or prey on, mountain yellow-legged frogs; and

(5) Destruction or alteration of mountain yellow-legged frog

habitat by dredging, channelization, diversion, in-stream vehicle

operation or rock removal, or other activities that result in the

destruction or significant degradation of cover, channel stability,

substrate composition, temperature, and habitat used by the species for

foraging, cover, migration, and breeding; and

(6) Discharges or dumping of toxic chemicals, silt, or other

pollutants into waters supporting mountain yellow-legged frogs by

mining, or other developmental or land management activities that

result in destruction or significant degradation of cover, channel

stability, substrate composition, temperature, and habitat used by the

species for foraging, cover, migration, and breeding.

Questions regarding whether specific activities may constitute a

violation of section 9 should be directed to the Field Supervisor of

our Carlsbad Fish and Wildlife Office (see ADDRESSES section). Requests

for copies of the regulations and inquiries regarding them may be

addressed to the U.S. Fish and Wildlife Service, Ecological Services,

Endangered Species Permits, 911 Northeast 11th Avenue, Portland, Oregon

97232-4181 (503/231-6241; FAX 503/231-6243).

Permits may be issued to carry out otherwise prohibited activities

involving endangered wildlife species under certain circumstances.

Regulations governing these permits are at 50 CFR 17.22 and 17.23. Such

permits are available for scientific purposes, to enhance the

propagation or survival of the species, for incidental take in

connection with otherwise lawful activities, and/or for economic

hardship.

Public Comments Solicited

The Service intends that any final action resulting from this

proposal will be as accurate and as effective as possible. Therefore,

comments or suggestions from the public, other concerned governmental

agencies, the scientific community, industry, or any other interested

party concerning this proposed rule are hereby solicited. Comments

particularly are sought concerning:

(1) Biological, commercial trade, or other relevant data concerning

any threat (or lack thereof) to this species;

(2) The distribution of resident rainbow trout in the mountains of

southern California prior to the stocking programs of the California

Department of Fish and Game;

(3) The location of any additional occurrences of this species and

the reasons why any habitat should or should not be determined to be

critical habitat as provided by section 4 of the Act;

(4) Additional information concerning the range, distribution, and

population size of this species; and

(5) Current or planned activities in the subject area and their

possible impacts on the southern California population of mountain

yellow-legged frogs.

Final promulgation of the regulation(s) on this species will take

into consideration the comments and any additional information received

by the Service. Such communications may lead to a final regulation that

differs from this proposal.

The Endangered Species Act provides for one or more public hearings

on this proposal, if requested. Requests must be received within 45

days of the date of publication of the proposal in the Federal

Register. Such requests must be made in writing and addressed to

Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife

Office (see ADDRESSES section).

National Environmental Policy Act

The U.S. Fish and Wildlife Service has determined that

environmental assessments and environmental impact statements, as

defined under the authority of the National Environmental Policy Act of

1969, need not be prepared in connection with regulations adopted

pursuant to section 4(a) of the Endangered Species Act of 1973, as

amended. A notice outlining the Service's reasons for this

determination was published in the Federal Register on October 25, 1983

(48 FR 49244).

References Cited

A complete list of all references cited herein are available upon

request from the Carlsbad Field Office (see ADDRESSES above).

Author

The primary author of this document is Paul J. Barrett, Carlsbad

Fish and Wildlife Office (see ADDRESSES section).

List of Subjects in 50 CFR Part 17

Endangered and threatened species, Exports, Imports, Reporting and

recordkeeping requirements, Transportation.

Proposed Regulation Promulgation

Accordingly, we propose to amend part 17, subchapter B of chapter

I, title 50 of the Code of Federal Regulations, as set forth below:

PART 17--[AMENDED]

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

Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C.

4201-4245; Pub. L. 99-625, 100 Stat. 3500, unless otherwise noted.

[[Page 71722]]

2. Section 17.11(h) is amended by adding the following, in

alphabetical order under AMPHIBIANS, to the List of Endangered and

Threatened Wildlife to read as follows:

Sec. 17.11 Endangered and threatened wildlife.

* * * * *

(h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------

Species Vertebrate

-------------------------------------------------------- population where Critical Special

Historic range endangered or Status When listed habitat rules

Common name Scientific name threatened

--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * * * *

Amphibians

* * * * * * *

Frog, mountain yellow-legged..... Rana muscosa........ U.S.A. (California, U.S.A., southern E ........... NA NA

Nevada) including California.

San Diego, Orange,

Riverside, San

Bernardino, and

Los Angeles

Counties.

* * * * * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------

Dated: December 10, 1999.

Jamie Rappaport Clark,

Director, U.S. Fish and Wildlife Service.

[FR Doc. 99-33087 Filed 12-17-99; 11:48 am]

BILLING CODE 4310-55-P