Endangered and Threatened Wildlife and Plants; Proposed Endangered Status for the California Red-legged Frog

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AC34

Endangered and Threatened Wildlife and Plants; Proposed

Endangered Status for the California Red-legged Frog

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: The U.S. Fish and Wildlife Service (Service) proposes to

determine the California red-legged frog (Rana aurora draytonii) as

endangered pursuant to the Endangered Species Act of 1973, as amended

(Act). The California red-legged frog is found primarily in wetlands

and streams in coastal drainages of central California. It has been

extirpated from 75 percent of its former range. This subspecies is

threatened throughout its remaining range by a wide variety of human

impacts, including urban encroachment, construction of reservoirs and

water diversions, introduction of exotic predators and competitors, and

stochastic events. This proposed rule, if made final, would extend the

Act's protection to the California red-legged frog. The Service seeks

data and comments from the public on this proposed rule.

DATES: Comments from all interested parties must be received by April

4, 1994. Public hearing requests must be received by March 21, 1994.

ADDRESSES: Written comments and materials concerning this proposed rule

should be submitted to the Field Supervisor, Sacramento Field Office,

U.S. Fish and Wildlife Service, 2800 Cottage Way, room E-1803,

Sacramento, California 95825-1846. Comments and materials received will

be available for public inspection, by appointment, during normal

business hours at the above address.

FOR FURTHER INFORMATION CONTACT: Mr. Wayne S. White, State Supervisor,

at the above address or telephone 916/978-4613.

SUPPLEMENTARY INFORMATION:

Background

The California red-legged frog (Rana aurora draytonii) is one of

two subspecies of the red-legged frog (Rana aurora) found on the

Pacific coast. R. a. draytonii was first described by Baird and Girard

in 1852 from specimens collected at or near the city of San Francisco

(Storer 1925). The historical range of the California red-legged frog

extended from the vicinity of Point Reyes National Seashore, Marin

County, California, coastally and from the vicinity of Redding, Shasta

County, California, inland southward to northwestern Baja California,

Mexico (Jennings and Hayes 1985, Hayes and Krempels 1986). The northern

red- legged frog (Rana aurora aurora) ranges from Vancouver Island,

British Columbia, Canada, south along the Pacific coast west of the

Cascade ranges to northern California (Del Norte County). Red-legged

frogs found in the intervening area (Humboldt to northern Marin County)

between the two subspecies exhibit intergrade characteristics of both

R. a. aurora and R. a. draytonii (Hayes and Krempels 1986). Systematic

relationships between the two subspecies are not completely understood

(Hayes and Miyamoto 1984, Green 1985a, Green 1986, Hayes and Krempels

1986). However, significant morphological and behavioral differences

between the two subspecies suggest that they may actually be two

species in secondary contact (Hayes and Krempels 1986).

Northern Marin County represents the approximate dividing line

between Rana aurora draytonii and intergrade populations along the

coastal range (M. Jennings, pers. comm., 1993). California red-legged

frogs found in Nevada (Linsdale 1938, Green 1985b) were introduced.

This rule would not extend the Act's protection to any Rana aurora in

Humboldt, Trinity, and Mendocino Counties, California, and Sonoma

County, California, north and west of 38 deg.30' N and 123 deg. W, as

well as the introduced population in Nevada.

The California red-legged frog is the largest native frog in the

western United States (Wright and Wright 1949), ranging from 4 to 13

centimeters (1.5 to 5.1 inches) in length (Stebbins 1985). The abdomen

and hind legs of adults are red; the back is characterized by small

black flecks and larger irregular dark blotches with indistinct

outlines on a brown, gray, olive, or reddish background color. Dorsal

spots usually have light centers (Stebbins 1985). Dorsolateral folds

are prominent on the back. Larvae range from 14 to 80 millimeters (mm)

(0.6 to 3.1 inches) in length, and the background color of the body is

dark brown and yellow with darker spots (Storer 1925).

Several morphological and behavioral characteristics differentiate

California red-legged frogs from northern red-legged frogs. Adult

California red-legged frogs are significantly larger than northern red-

legged frogs by 35 to 40 mm (1.4 to 1.6 inches) (Hayes and Miyamoto

1984). Dorsal spots of northern red-legged frogs usually lack light

centers common to California red-legged frogs (Stebbins 1985), but this

is not a strong diagnostic character. California red-legged frogs have

paired vocal sacs and call in air (Hayes and Krempels 1986), whereas

northern red-legged frogs lack vocal sacs (Hayes and Krempels 1986) and

call underwater (Licht 1969). Female California red-legged frogs

deposit egg masses on emergent vegetation so that the egg mass floats

on the surface of the water (Hayes and Miyamoto 1984). Northern red-

legged frogs also attach their egg masses to emergent vegetation, but

the mass is submerged (Licht 1969). California red-legged frogs breed

from November to March with earlier breeding records occurring in

southern localities (Storer 1925). California red-legged frogs found in

coastal drainages are rarely inactive (Jennings et al. 1992), whereas

those found in interior sites may hibernate (Storer 1925).

The California red-legged frog occupies a fairly distinct habitat,

combining both specific aquatic and riparian components (Hayes and

Jennings 1988, Jennings 1988b). The adults require a dense, shrubby or

emergent riparian vegetation closely associated with deep (>0.7 meters)

still or slow moving water (Jennings et al. 1992). The largest

densities of California red-legged frogs currently are associated with

deep-water pools with dense stands of overhanging willows (Salix spp.)

and an intermixed fringe of cattails (Typha latifolia) (Jennings

1988b). Well-vegetated terrestrial areas within the riparian corridor

may provide important sheltering habitat during winter. California red-

legged frogs estivate in small mammal burrows and moist leaf litter up

to 26 meters (85 feet) from water in dense riparian vegetation (Rathbun

et al. 1993).

Egg masses that contain about 2,000 to 5,000 moderate-sized (2.0 to

2.8 mm (0.08 to 0.11 inches) in diameter), dark reddish brown eggs are

typically attached to vertical emergent vegetation, such as bulrushes

(Scirpus spp.) or cattails (Typha spp.) (Jennings et al. 1992). Eggs

hatch in 6 to 14 days (Jennings 1988b). The most significant mortality

factor in the pre-hatching stage is water salinity (Jennings et al.

1992). One hundred percent mortality occurs in eggs exposed to salinity

levels greater than 4.5 parts per thousand (Jennings and Hayes 1990).

Larvae undergo metamorphosis 3.5 to 7 months after hatching (Storer

1925, Wright and Wright 1949, Jennings and Hayes 1990). Of the various

life stages, larvae probably experience the highest mortality rates,

with less than 1 percent of eggs laid reaching metamorphosis (Jennings

et al. 1992). Sexual maturity is reached at 3 to 4 years of age (Storer

1925, Jennings and Hayes 1985). California red-legged frogs may live 8

to 10 years (Jennings et al. 1992).

The diet of California red-legged frogs is highly variable. Hayes

and Tennant (1985) found invertebrates to be the most common food

items. Vertebrates, such as Pacific tree frogs (Hyla regilla) and

California mice (Peromyscus californicus), represented over half of the

prey mass eaten by larger frogs (Hayes and Tennant 1985). Hayes and

Tennant (1985) found juvenile frogs to be active diurnally and

nocturnally, whereas adult frogs were largely nocturnal. Feeding

activity probably occurs along the shoreline and on the surface of the

water (Hayes and Tennant 1985). Larvae probably eat algae (Jennings et

al. 1992).

California red-legged frogs have sustained a 75 percent reduction

in their geographic range in California as a result of several factors

acting singly or in combination (Jennings et al. 1992). Habitat loss

and alteration, combined with overexploitation and introduction of

exotic predators, were significant factors in the California red-legged

frog decline in the early to mid 1900s. California red-legged frogs

were extirpated from the Central Valley probably in the 1960s.

Remaining aggregations of California red-legged frogs in the Sierran

foothills became fragmented and were later eliminated by reservoir

construction, continued expansion of exotic predators, grazing, and

drought. The pattern of disappearance of California red-legged frogs in

southern California is similar to that seen in the Central Valley,

except that urbanization and its associated roadway, large reservoir

(exotic predators), and stream channelization projects were the primary

factors causing population declines.

At present, California red-legged frogs are known to occur in about

190 streams or drainages from 15 counties in central and southern

California. Monterey, San Luis Obispo and Santa Barbara Counties

support the greatest amount of currently occupied habitat. The most

secure aggregations of California red-legged frogs are found in aquatic

sites that support substantial riparian and aquatic vegetation and lack

exotic predators (e.g., bullfrogs, mosquitofish, largemouth and

smallmouth bass). The majority of aggregations are threatened, however,

by expansion of exotic predators, proposed residential development,

water storage projects, and other factors. For example, within the

Central Valley hydrographic basin, only six drainages, all on the Coast

range slope of the San Joaquin Valley, are known or likely to support

California red-legged frogs, compared to over 60 historic locality

records for this basin. Two of these drainages, known to support

significant numbers of California red-legged frogs, are sites of

proposed large reservoir projects. Also, in southern California,

California red-legged frogs are known from only 4 locations south of

the Tehachapi Mountains, compared to over 80 historic locality records

for this region. Only three areas currently support more than 350

adults.

Previous Federal Action

On January 29, 1992, the Service received a petition from Drs. Mark

R. Jennings, Marc P. Hayes, and Dan C. Holland to list the California

red-legged frog (Rana aurora draytonii). The petition specified

endangered or threatened status by distinct drainages (watersheds)

within the range of the species. On October 5, 1992, the Service

published a 90-day petition finding (57 FR 45761) that substantial

information had been presented indicating the requested action may be

warranted. Public comments were requested on the status of this

species. The California red-legged frog had been included as a Category

1 candidate species in the Service's November 21, 1991, Animal Notice

of Review (56 FR 58804). Category 1 candidates are species for which

the Service has substantial information on biological vulnerability and

threat to support proposals to list them as endangered or threatened.

On July 19, 1993, the Service published a 12-month finding on the

petitioned action (58 FR 38553). This finding indicated that listing of

the California red-legged frog was warranted and that a proposed rule

would be published promptly.

Summary of Factors Affecting the Species

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

and regulations (50 CFR part 424) promulgated to 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 California

red-legged frog (Rana aurora draytonii) are as follows:

A. The present or threatened destruction, modification, or

curtailment of its habitat or range. Herpetologists have noted the

decline or extirpation of California red-legged frogs from the San

Francisco Bay area (Sean J. Barry, University of California, Davis, in

litt., 1992; Robert C. Stebbins, University of California, Berkeley, in

litt., 1993; John S. Applegarth, herpetologist, in litt., 1993; Ed Ely,

herpetologist, in litt., 1993), the Salinas River drainage (Lawrence E.

Hunt, University of California, Santa Barbara, in litt., 1993), the San

Luis Obispo, Santa Barbara, and Ventura County area (Aryan I. Roest,

California Polytechnic State University, San Luis Obispo, in litt.,

1993; Samuel S. Sweet, University of California, Santa Barbara, in

litt., 1993), southern California (Patrick McMonagle, herpetologist, in

litt., 1993; John D. Goodman, zoologist, in litt., 1992; Robert B.

Sanders, San Bernardino County Museum, in litt., 1992; John Stephenson,

U.S. Forest Service, in litt., 1993; Michael C. Long, Eaton Canyon Park

Nature Center, in litt., 1992; Joseph F. Copp, herpetologist, in litt.,

1993; Glenn R. Stewart, California Polytechnic University, Pomona, in

litt., 1993; Walter B. Allen, herpetologist, in litt., 1993; Robert

Fisher, University of California, Davis, in litt., 1993), central

California (Martin R. Brittan, California State University, Sacramento,

in litt., 1993), and the northern and southern Sierra Nevada foothills

(Jay Wright, Feather River College, Quincy, in litt., 1993; Alan M.

McCready, California State University, Sacramento, in litt., 1992).

These observations and data provided by the petitioners indicate

that the California red-legged frog has sustained a 75 percent

reduction in its geographic range in California. Large aggregations of

greater than 350 adults currently are known from only three areas:

Pescadero Marsh Natural Preserve in coastal San Mateo County, Point

Reyes National Seashore in Marin County, and canals west of San

Francisco International Airport in the San Francisco Bay area (Jennings

et al. 1992).

Habitat loss and alteration are primary factors that have

negatively affected the California red-legged frog throughout its

range. In the Central Valley of California, over 90 percent of historic

wetlands have been diked, drained, or filled primarily for agricultural

development and secondarily for urban development (U.S. Fish and

Wildlife Service 1978). Much of the wetland habitat lost, such as in

the San Joaquin Valley, was prime habitat for the California red-legged

frog (Jennings and Hayes 1984). Wetland alterations, including stream

channelization, clearing of vegetation, and water diversions that often

accompanied agricultural development, rendered remaining aquatic sites

unsuitable for California red-legged frogs. As a result, California

red-legged frogs on the floor of the Central Valley were eliminated

probably sometime before 1960 (Jennings et al. 1992). Remaining

aggregations in drainages around the Central Valley became isolated and

fragmented.

Historically, urbanization with its associated roadway, stream

channelization, and large reservoir construction projects also has

significantly altered or eliminated California red-legged frog habitat,

with the greatest impact occurring in southern California. South of the

Tehachapi Mountains in southern California, the California red-legged

frog remains at only 4 of over 80 sites where it was found historically

(Jennings et al. 1992). No California red-legged frogs were found

during amphibian surveys in 1993 in Cleveland National Forest in

southern California (J. Stephenson, pers. comm., 1993).

Urbanization poses a significant threat to the California red-

legged frog. On the central California coast and south San Francisco

Bay area, the Service is aware of numerous proposed residential

developments that would degrade known California red-legged frog

habitat either directly through on-site degradation of the stream

environment or indirectly through instream flow reductions to

accommodate new urban growth (U.S. Fish and Wildlife Service unpubl.

data). These projects include the East County Area Plan in Alameda

County, which involves development of up to 52,000 acres, and projects

currently proposed in the Ruby Hills/Arroyo Del Valle watershed and

south Livermore Valley; Reservoir Canyon ponds in Santa Clara County;

Alamo, Shadow, and Brookside Creeks in Contra Costa County; Potrero,

San Clemente, and San Jose Creeks and the Carmel River in Monterey

County; and the Santa Ynez River in Santa Barbara County. In San Luis

Obispo County, one of three counties with numerous drainages supporting

California red-legged frogs, proposed residential and/or recreational

development adjacent to San Simeon, Santa Rosa, San Juan, Chorro, and

Cambria Meadows Creeks and Estrella and Salinas Rivers would degrade or

eliminate California red- legged frog habitat. Updates to area plans

for the North Coast, San Luis Obispo, and Paso Robles/Atascadero areas

in San Luis Obispo County propose rezoning of over 240,000 acres

primarily for urban development. Between the cities of Ventura and San

Luis Obispo, development already has eliminated California red-legged

frogs from at least eight drainages along the coast (Galen B. Rathbun

and Mark R. Jennings, U.S. Fish and Wildlife Service, in litt., 1993).

Historic water projects, which accompanied urban and agricultural

growth, also had a negative effect on California red-legged frogs.

Construction of reservoirs, such as Lake Oroville, Whiskeytown

Reservoir, Don Pedro Reservoir, Lake Berryessa, San Luis Reservoir,

Lake Silverwood, Lake Piru, Pyramid Lake, and Lower Otay Lake, directly

eliminated California red-legged frog habitat or fragmented remaining

aggregations (Jennings et al. 1992). Reservoirs also typically are

stocked with exotic species of fish and the introduced bullfrog (Rana

catesbeiana). These species often expand into previously isolated

California red-legged frog habitat. The timing and duration of water

releases from reservoirs, particularly on the central California coast,

can render a stream unsuitable for California red-legged frog

production (M. Jennings, in litt., 1993) or maintain aggregations of

exotic predators in downstream areas that would normally be dry in

summer (S. Sweet, in litt., 1993). Hayes and Jennings (1988) found that

California red-legged frogs generally were extirpated from a drainage 1

to 5 years after filling of a reservoir. See Factor C below for further

discussion of exotic predators.

A variety of proposed water projects threaten remaining California

red-legged frog populations. Construction of major reservoirs is

proposed on Los Banos Creek (Merced County), with Orestimba Creek

(Stanislaus County) as an alternative reservoir site (California

Department of Water Resources and the U.S. Bureau of Reclamation 1990),

and on Kellogg Creek (Contra Costa County) (Contra Costa Water District

1993). These sites represent three of six sites remaining in the

Central Valley hydrographic basin with known or potential aggregations

of California red-legged frogs. On the Salinas River on the central

coast, raising the height of Salinas Dam (Santa Margarita Lake) is

proposed in San Luis Obispo County. Reservoir construction at this site

may allow exotic predators access to formerly secure aggregations of

California red-legged frogs isolated in upper portions of the watershed

(L. Hunt, in litt., 1993). Other large reservoir projects proposed in

California red-legged frog habitat include the Upper Nacimiento River

Project and Arroyo Seco Dam Project in Monterey County. In Santa

Barbara and Ventura Counties, proposed dams on the Santa Ynez River,

Sisquoc River, and Sespe Creek also would eliminate or degrade

California red-legged frog habitat (S. Sweet, pers. comm., 1993).

Proposed or existing water diversions, well development, or small

reservoir construction projects to supply residential uses on the

central coast (e.g., San Simeon, Santa Rosa, Van Gordon, Villa, San

Luis Obispo, Chorro, Pico, and Little Pico Creeks, Arroyo del Puerta,

and Arroyo Laguna in San Luis Obispo County; the Carmel and Salinas

River drainage basins in Monterey County; Canada de Refugio in Santa

Barbara County) reduce instream flows and, when combined with drought,

degrade or eliminate riparian habitat and create stressful conditions

for California red-legged frogs. See Factor E below for additional

discussion of the effects of drought. Small reservoirs also serve as a

source of exotic fishes and bullfrogs (G. Rathbun and M. Jennings, in

litt., 1993). The proposed coastal branch of the State Water Project

likely would result in a number of adverse effects to California red-

legged frogs in many of the 24 areas receiving State water, including

(1) altered water regimes in existing and any proposed delivery

facilities of individual water districts, (2) spills, leaks,

malfunctions, and operational errors that lead to introduction of

exotic predators into isolated stream segments currently occupied by

California red-legged frogs, and (3) indirect effects associated with

expanded urbanization.

Storm damage repair and flood control maintenance of streams is a

widespread and ongoing threat to California red-legged frogs. Routine

flood control maintenance includes vegetation removal, herbicide

spraying, shaping of banks to control erosion, and desilting of the

creek. All of these activities degrade California red-legged frog

habitat. In San Luis Obispo and Santa Barbara Counties, maintenance

work is planned for 14 and 11 drainages, respectively. All 25 drainages

are known to be inhabited by California red-legged frogs. In Santa

Barbara County, a larger channel maintenance project is proposed for a

4.5-mile stretch of the Santa Ynez River near Lompoc and a 10-mile

segment of San Antonio Creek, both of which support California red-

legged frog habitat. Channel maintenance at San Francisco International

Airport threatens one of the three largest remaining aggregations of

this subspecies.

Regular road maintenance activities involving grading in or

adjacent to California red-legged frog habitat can result in increased

siltation in the stream. If this siltation occurs during the breeding

season, asphyxiation of eggs and small California red-legged frog

larvae can result. On the upper Santa Ynez River and Sespe Creek in Los

Padres National Forest, Sweet (pers. comm., 1993) observed California

red-legged frog egg masses smothered with silt.

Livestock grazing is another form of habitat alteration that is

contributing to declines in the California red-legged frog. Jennings et

al. (1992) found livestock grazing to occur at all known historic

locations of the California red-legged frog in the Central Valley

hydrographic basin. Livestock grazing also has been implicated as a

contributing factor in the decline and disappearance of California red-

legged frogs from the lower Salinas River (L. Hunt, in litt., 1993) and

the San Francisco peninsula (S. Barry, in litt., 1992). Two remaining

aggregations of California red-legged frogs in the Central Valley

hydrographic basin (Corral Hollow Ecological Reserve and Frank Raines

Regional Park) are threatened by sedimentation of aquatic habitats

either directly or indirectly caused by livestock grazing and off-road

vehicle use (Jennings et al. 1992). Rathbun (pers. comm., 1993) reports

that grazing is adversely altering California red-legged frog habitat

on Pico, Van Gordon, San Simeon, Santa Rosa, Cambria Meadows, and

Cayucos Creeks in San Luis Obispo County.

Numerous studies, summarized in Behnke and Raleigh (1978) and

Kauffman and Krueger (1984), have shown that livestock grazing

negatively affects riparian habitat. Cattle have a disproportionately

greater adverse affect on riparian and other wetland habitats because

they tend to concentrate in these areas, particularly during the dry

season (Marlow and Pogacnik 1985). Cattle trample and eat emergent and

riparian vegetation, often eliminating or severely reducing plant cover

(Gunderson 1968, Duff 1979). Loss of riparian vegetation results in

increased water temperatures (Van Velson 1979), which encourage

bullfrog reproduction (bullfrogs are a predator and competitor of

California red-legged frogs). Riparian vegetation loss due to cattle

grazing includes the loss of willows (Duff 1979), which are associated

with the highest densities of California red-legged frogs (Jennings

1988b). Cattle grazing also results in increased erosion in the

watershed (Lusby 1970, Winegar 1977), which results in the

sedimentation of deep pools (Gunderson 1968) used by California red-

legged frogs and adversely affects aquatic invertebrates (Cordone and

Kelley 1961), which are common prey items of California red-legged

frogs.

Off-road vehicle use adversely affects California red-legged frogs

in ways similar to livestock grazing. Off-road vehicles damage riparian

vegetation and increase siltation in pools. Off-road vehicles also

disturb the water in stream channels and may crush eggs, larvae,

juveniles or adults. California red-legged frogs were eliminated either

all or in part by off-road vehicle activities at the Mojave River above

Hesperia, at Rincon Station on the San Gabriel River, and at Piru Creek

above Pyramid Lake (M. Jennings, pers. comm., 1993).

Timber harvest threatens California red-legged frogs through loss

of riparian vegetation, which is needed for cover and water temperature

regulation, and increased erosion in the watershed, which fills pools

with sediment and smothers egg masses. In Santa Cruz County, timber

harvest is proposed adjacent to Adams Creek (Celia Scott, private

citizen, pers. comm., 1993), 1 of 12 remaining streams in the county

that support California red-legged frogs.

B. Overutilization for commercial, recreational, scientific, or

educational purposes. Records of harvesting California red-legged frogs

for food date back to an account by Lockington (1879) of the commercial

harvest of this species for the San Francisco market. From 1890 to

1900, the California red-legged frog supported a significant commercial

fishery (Smith 1895) with about 80,000 frogs harvested annually

(Jennings and Hayes 1984). Counties surrounding San Francisco Bay

provided the bulk of the frog harvest in the early to mid 1890s, with

the Sacramento and San Joaquin Valleys increasing in importance by the

end of the decade (Chamberlain 1898, Jennings and Hayes 1985). By 1900,

harvest figures for California red-legged frogs fell dramatically,

indicating that overharvesting may have occurred. Jennings and Hayes

(1985) hypothesized that this rapid decline in the California red-

legged frog population was the result of selective harvesting of the

larger females. Introduction of the bullfrog in California in 1896 was

probably in response to the dwindling California red-legged frog

population (Jennings and Hayes 1985).

Prior to 1950, California red-legged frogs were used sporadically

for research in high schools and universities. At present, the

California red-legged frog is sold commercially from suppliers located

outside California in the pet trade. Because the State of California

prohibits possession of wild California red-legged frogs, frogs sold in

the pet trade presumably are reared in captivity (M. Jennings, pers.

comm., 1993). However, California red-legged frogs occur in isolated

and fragmented wetland habitat on private property and are at risk from

vandalism.

C. Disease or predation. There have been no documented instances of

disease adversely affecting the California red-legged frog.

Few data are available on the effect of native predators on the

California red-legged frog. Bitterns (Botaurus lentiginosus) and black-

crowned night herons (Nycticorax nycticorax) are likely predators of

adult frogs (Jennings and Hayes 1990). Juvenile California red-legged

frogs, which are more active diurnally and less wary than adults, may

be more susceptible to predation by diurnal predators, such as the

great blue heron (Ardea herodias) and several species of garter snakes

(Thamnophis sp.) (Fitch 1940, Fox 1952), including the endangered San

Francisco garter snake (Thamnophis sirtalis tetrataenia) (Barry 1978,

Wharton et al. 1986). Recent post-metamorphs also may be particularly

vulnerable to predation by garter snakes, as was found in other species

of ranid frogs by Arnold and Wassersug (1978).

Introduced predators of particular concern are the bullfrog, red

swamp crayfish (Procambarus clarkii), signal crayfish (Pacifastacus

leniusculus), and several species of fish, including bass (Micropterus

spp.), catfish (Ictalurus spp.), sunfish (Lepomis spp.), and

mosquitofish (Gambusia affinis) (Moyle 1973; Hayes and Jennings 1986,

1988). All species were introduced into California in the late 1800s

and early 1900s, and through range expansions, reintroductions, and

transplants have become established throughout most of the state

(Riegel 1959, Bury and Luckenbach 1976, Moyle 1976).

Several researchers in central California have noted the decline

and eventual disappearance of California red-legged frogs once

bullfrogs become established at the same site (L. Hunt, in litt, 1993;

S. Barry, in litt., 1992; S. Sweet, in litt., 1993). Moyle (1973)

attributed the disappearance of California red-legged frogs from the

San Joaquin Valley and Sierran foothill region primarily to a

combination of bullfrog predation and competition. All sites in the

Sierra Nevada mountains that supported California red-legged frogs in

the 1970s now are inhabited by bullfrogs (M. Jennings, in litt., 1993).

Over 65 percent of the streams or drainages currently known to support

California red-legged frogs also are inhabited by bullfrogs, either in

association with California red-legged frogs or in other portions of

the drainage. Over the last decade, Jennings (in litt., 1993) has

observed bullfrogs moving upstream and/or downstream into formerly

isolated California red-legged frog habitat in a number of drainages,

including streams in Ventura, Santa Barbara, San Luis Obispo, Merced,

Stanislaus, and San Mateo Counties. Game fish are introduced into

drainages by stocking of reservoirs and ponds, dispersal and

colonization, conveyance of project water from other streams inhabited

by these exotics, and releases by individuals. At The Nature

Conservancy Santa Rosa Plateau Reserve in Riverside County (the only

site south of the Santa Clara River supporting California red-legged

frogs), a docent found a school teacher attempting to introduce

bullfrog tadpoles into the preserve in the 1980s (M. Jennings, in

litt., 1993). Once established, it is virtually impossible to eliminate

bullfrogs (M. Jennings, in litt., 1993; Cecil Schwalbe, National Park

Service, Tuscon, Arizona, pers. comm., 1993; Frank Slavens, Woodland

Park Zoological Gardens, Seattle, Washington, pers. comm., 1993).

Bullfrogs prey on California red-legged frogs (Twedt 1993; S.

Sweet, in litt., 1993) and other amphibians and aquatic reptiles

(Schwalbe and Rosen 1988). Twedt (1993) documented 4 juvenile red-

legged frogs in the contents of a total of 22 adult bullfrog stomachs.

He also found a subadult bullfrog in one of the adult bullfrog

stomachs; this prey item was between the size of an adult male

(approximately 55 millimeters (2 inches)) and adult female

(approximately 70 millimeters (3 inches)) red-legged frog, indicating

that bullfrogs also undoubtedly prey on adult red-legged frogs.

Bullfrogs may have a competitive advantage over red-legged frogs

because of their (1) larger size, (2) generalized food habits (Bury and

Whelan 1984), (3) extended breeding season (Storer 1933), which allows

for production of two clutches of eggs during a breeding season (Emlen

1977), (4) apparent olfactory rejection of larvae by predatory fish

(Kruse and Francis 1977), and (5) diminished activity periods (Woodward

1983), which also reduces their exposure to predators. Bullfrogs also

interfere with red-legged frog reproduction. Several researchers have

noted red-legged frogs in amplexus (mounted on) with bullfrogs

(Jennings and Hayes 1990; Twedt 1993; M. Jennings, in litt., 1993;

Stebbins in litt., 1993). However, the extent to which bullfrog

predation, competition, and reproductive interference adversely affects

red-legged frogs has not been studied in the field (Hayes and Jennings

1986). Habitat alterations, including removal of riparian or aquatic

vegetation, reduced stream flows, and sedimentation of pools, often

provide conditions detrimental to red-legged frogs but favorable to

bullfrogs (Hayes and Jennings 1986; Jennings, pers. comm., 1993).

Hayes and Jennings (1986, 1988) noted an inverse correlation

between the abundance of introduced fish species and red-legged frogs.

Aquatic sites where introduced fishes were abundant rarely had native

ranids, and when present, ranid populations were small. A similar

negative correlation was reported by Hunt (in litt., 1993) for red-

legged frogs in the Salinas River drainage and by Moyle (1973) for the

foothill yellow-legged frog (Rana boylii). Stocking of warm water game

fish is often included as a mitigation measure in proposed reservoir

projects. Results of a recent study indicate that, despite their small

size, mosquitofish do prey on and incapacitate red-legged frog tadpoles

by eating their fins. This mosquitofish predation may be more

significant than predation by bluegill (Lepomis macrochirus) or

bullfrogs (Michael Soule and Randy Schmieder, University of California,

Santa Cruz, pers. comm., 1993). Mosquitofish have become established

statewide and are stocked routinely by mosquito abatement districts as

a control measure (Moyle 1976). The demonstrated adverse effects and

widespread distribution of alien fishes on red-legged frogs indicate

that fish introductions are one of the primary threats to the survival

of the species.

D. The inadequacy of existing regulatory mechanisms. In 1972, the

California Fish and Game Commission amended its sport fishing

regulations to prohibit take or possession of California red-legged

frogs (Bury and Stewart 1973). This law, however, provides no

protection for habitat of the California red-legged frog. The

California red-legged frog also is classified as a ``Species of Special

Concern'' in California (Steinhart 1990). This designation, however,

provides no special, legally mandated protection.

The Clean Water Act (section 404) is the primary Federal law that

could provide some protection for aquatic habitats of the California

red-legged frog if the habitats are determined by the U.S. Army Corps

of Engineers (Corps) to be jurisdictional areas (i.e., waters of the

United States). Under section 404, nationwide permits, which undergo

minimal public and agency review, can be issued for projects involving

less than 10 acres of wetlands above the headwaters (i.e., streams with

less than 5 cubic feet per second (cfs) mean annual flow) or for

isolated waters, unless a listed species may be adversely affected.

Many aggregations of California red-legged frogs occur in isolated

wetlands and coastal streams that may have mean annual flows less than

5 cfs. Individual permits, which are subject to more extensive review,

could be required for projects that have more than minimal impacts to

waters of the United States. The Clean Water Act does not afford any

special protection for candidate species. However, if the California

red-legged frog is listed, the Corps would be required by section 7 of

the Act to consult and obtain the concurrence of the Service prior to

the authorization of any section 404 permit.

Federal lands, including those of the Forest Service, National Park

Service, Bureau of Land Management, and Department of Defense,

encompass approximately 10 percent of the current known range of the

California red-legged frog. Multiple land use management, as currently

practiced by the Forest Service, Bureau of Land Management, and

National Park Service, does not provide long-term protection for the

California red-legged frog.

E. Other natural or man-made factors affecting its continued

existence. Four consecutive years of drought in California (1986-1990)

severely affected remaining California red-legged frogs in the Sierra

foothills. According to the petitioners, several thousand hours of

field surveys have revealed only one California red-legged frog since

1985 (Jennings et al. 1992). Many sites in intermittent streams that

held California red-legged frogs before the drought were completely dry

during field surveys. Sites still holding pools of water had water

levels so low that access by predators was enhanced. Livestock grazing

at many sites exacerbated effects of the drought by limiting or

preventing riparian habitat regeneration (Jennings et al. 1992).

Jennings et al. (1992) concluded that California red-legged frogs have

been extirpated from the Sierra Nevada foothills or are extremely rare

and vulnerable. Amphibian surveys of Sierran National Forests in 1992

revealed no California red-legged frogs (David Martin, University of

California, Santa Barbara, pers. comm., 1993).

On the central California coast, drought also may play a role in

decreased California red-legged frog reproduction where frogs occur in

coastal lagoons. At Pescadero Marsh Natural Preserve, Jennings and

Hayes (1990) found that many dead egg masses in a portion of the marsh

likely were killed by excessive (> 4.5 parts per thousand) salinity

levels. High salinities in the marsh were attributed to drought

conditions in the watershed. Rathbun et al. (1991) attributed the

absence of California red-legged frogs in lower Santa Rosa Creek and

lagoon in San Luis Obispo County to overallocation of instream flows

exacerbated by the drought. Increased salinities were recorded in

several other coastal lagoons during the drought years (C. Swift and K.

Worcester, pers. comm. in Jennings et al. 1992). In 1993, Jennings

(pers. comm., 1993) reported the loss of California red-legged frog egg

masses from increased salinity in Arroyo Laguna in San Luis Obispo

County. Because significant numbers of California red-legged frogs

occur in coastal lagoons on the central California coast, drought has

the potential to severely reduce production of California red-legged

frogs over a significant portion of their remaining range.

Reservoirs provide persistent habitat for bullfrogs during drought.

Once rains return, bullfrogs recolonize former habitat as reservoir

levels rise. Reservoirs, however, with their steep sides and lack of

critical riparian vegetation, are structurally unsuitable for the

California red-legged frog.

Periodic wildfires may adversely affect California red-legged frogs

by causing direct mortality, destroying streamside vegetation, or

eliminating vegetation that protects the watershed. The 1991 Lions Fire

on upper Sespe Creek in the Los Padres National Forest destroyed known

California red-legged frog habitat (S. Sweet, pers. comm., 1993).

Following the fire, extensive erosion in the watershed also negatively

affected California red-legged frogs (S. Sweet, pers. comm., 1993).

Extensive flooding has been implicated by Jennings and Hayes (in

press) as a significant contributing factor in the extirpation of the

California red-legged frog from desert drainages of southern

California. For example, in the Mojave River drainage, no verifiable

records or sightings exist of California red-legged frogs after 1968

(Jennings and Hayes in press). The disappearance of this species from

the drainage coincided with a catastrophic flood event in the Mojave

River in the winter of 1968-1969.

The high degree of fragmentation of remaining California red-legged

frog habitat makes this subspecies especially vulnerable to random

extinction events and to loss of genetic variability. Small population

size increases rates of inbreeding and may allow expression of

deleterious recessive genes occurring in the population (known as

``inbreeding depression''). Loss of genetic variability, through random

genetic drift, reduces the ability of small populations to respond

successfully to environmental stresses. In the remaining vestiges of

its former habitat and with its potentially reduced genetic

variability, the California red-legged frog is vulnerable to random or

stochastic events, such as fluctuations or variations of annual weather

patterns (as discussed above), availability of food, predation and

associated demographic uncertainty, or other environmental stresses.

With only three areas currently supporting over 350 adults, all

remaining populations of the species are considered vulnerable to

stochastic threats.

The Service carefully has assessed the best scientific and

commercial information available regarding the past, present, and

future threats faced by the California red-legged frog in determining

to propose this rule. Based on this evaluation, the preferred action is

to list the California red-legged frog (Rana aurora draytonii) as

endangered. This subspecies has been extirpated from 75 percent of its

former range. Seventy-seven percent of remaining aggregations currently

are threatened by one or more factors, including (1) introduction of

exotic predators and competitors, (2) urban encroachment, (3)

construction of large and small reservoirs, water diversions and well

development, (4) flood control maintenance, (5) grazing, and (6) timber

harvest. Only 44 drainages, with the majority being in Monterey, Santa

Barbara, and San Luis Obispo Counties, currently provide habitat free

from the above threats. Fragmentation of habitat, however, renders

these populations vulnerable to random extinction (stochastic) events.

For the reasons discussed below, critical habitat is not being proposed

at this time.

Critical Habitat

Section 4(a)(3) of the Act, as amended, and implementing

regulations (50 CFR 424.12) require that, to the maximum extent prudent

and determinable, the Secretary propose critical habitat at the time a

species is proposed to be endangered or threatened. The Service finds

that designation of critical habitat is not presently prudent for the

California red-legged frog.

As discussed under Factor B in the ``Summary of Factors Affecting

the Species'' section, the California red-legged frog has been and

continues to be threatened by taking, an activity difficult to control.

Listing of the frog may result in an increase in the threat of

vandalism, a concern expressed by the petitioners and other experts (M.

Jennings, S, Sweet, pers. comms., 1993). California red-legged frogs

occur in isolated and fragmented wetland habitat on private property

and are at risk from vandalism. Publication of specific localities,

which would be required in proposing critical habitat, would reveal

precise locality data and thereby make the species more vulnerable to

collection and acts of vandalism, and increase the difficulties of

enforcement. Protection of this species' habitat will be addressed in

the recovery process and through the section 7 consultation process.

Therefore, it would not now be prudent to determine critical habitat of

the California red-legged frog.

Available Conservation Measures

Conservation measures provided to species listed as endangered or

threatened under the Endangered Species Act include recognition,

recovery actions, requirements for Federal protection, and prohibitions

against certain activities. Recognition through listing encourages and

results in conservation actions by Federal, State, and private

agencies, groups, and individuals. The Act provides for possible land

acquisition and cooperation with the States and requires that recovery

actions be carried out for all listed species. The protection required

of Federal agencies and the prohibitions against taking and harm are

discussed, in part, below.

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) of the Act 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 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 that may be involved as a result of this proposed

rule are the Bureau of Reclamation, Bureau of Land Management, National

Park Service, Forest Service, and the Departments of the Army, Navy and

Air Force. At several parks, the National Park Service has conducted or

is planning to conduct surveys of California red-legged frogs on park

property (Daphne A. Hatch, National Park Service, in litt., 1993; James

Sleznick, National Park Service, in litt., 1992; Gary Fellers, National

Park Service, pers. comm., 1993). The Forest Service has conducted and

has ongoing amphibian surveys in many National Forests within the

historic range of the California red-legged frog (J. Stephenson, pers.

comm., 1993; D. Martin, pers. comm., 1993). The Bureau of Reclamation

is cosponsoring a proposed reservoir construction project (Los Vaqueros

Reservoir) on Kellogg Creek, Contra Costa County (Contra Costa Water

District 1993). A mitigation and monitoring program is proposed to

compensate for California red-legged frog habitat losses. The

mitigation plan includes a bullfrog and exotic fish control program to

be carried out for the life of the reservoir project (Contra Costa

Water District 1993). The potential for success of the mitigation plan

is unknown. The proposed Los Banos Grande reservoir project on Los

Banos Creek in Merced County, also cosponsored by the Bureau of

Reclamation, does not provide mitigation specifically for the

California red-legged frog (Cay Goude, Fish and Wildlife Service, pers.

comm., 1993). The U.S. Army Corps of Engineers would be involved

through their permitting authority under section 404 of the Clean Water

Act. Any of the above mentioned Federal agencies would be required to

consult with the Service if any action they fund, authorize, or carry

out is likely to jeopardize the continued existence of the California

red-legged frog.

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. With respect to the California red-legged frog,

these prohibitions, in part, 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 also is

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.

Permits may be issued to carry out otherwise prohibited activities

involving endangered and threatened wildlife species under certain

circumstances. Regulations governing 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, and/or for incidental take

in connection with otherwise lawful activities. Requests for

information on permits should be addressed to the Assistant Regional

Director, Ecological Services, U.S. Fish and Wildlife Service, 911 NE.

11th Avenue, Portland, Oregon 97232-4181 (503/231-6241; FAX 503/231-

6243).

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 the California red-legged frog;

(2) The location of any additional populations of the California

red-legged frog and the reasons why any habitat should or should not be

determined to be critical habitat as provided by section 4 of the Act;

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

population size of the California red-legged frog;

(4) Any examples of take or vandalism of California red-legged

frogs; and

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

possible impacts on the California red-legged frog.

Any final decision on this proposal will take into consideration

the comments and any additional information received by the Service,

and such communications may lead to a final regulation that differs

from this proposal.

The Endangered Species Act provides for a public hearing on this

proposal, if requested. Requests must be received within 45 days of the

date of publication of this proposal in the Federal Register. Such

requests must be made in writing and addressed to the Field Supervisor

of the Sacramento Field Office (see ADDRESSES section).

National Environmental Policy Act

The Fish and Wildlife Service has determined that an Environmental

Assessment, 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 is available upon

request from the Field Supervisor, Sacramento Field Office (see

ADDRESSES section).

Author

The primary author of this proposed rule is Karen J. Miller,

Sacramento Field Office (see ADDRESSES section), telephone 916/978-

4866.

List of Subjects in 50 CFR Part 17

Endangered and threatened species, Exports, Imports, Reporting and

recordkeeping requirements, Transportation.

Proposed Regulation Promulgation

Accordingly, the Service hereby proposes 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, 10080 Stat. 3500, unless otherwise noted.

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

---------------------------------------------------- Historic range where endangered or Status When listed Critical Special

Common name Scientific name threatened habitat rules

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

* * * * * * *

* * * * * * *

Amphibians

Frog, California red- Rana aurora draytonii... U.S.A. (CA)............. Entire (excluding E ........... NA NA

legged. populations in

Humboldt, Trinity, and

Mendocino Cos., CA;

Sonoma Co, CA, north

and west of 38 deg. 30'

N, 123 deg. W; and NV).

* * * * * * *

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

Dated: January 26, 1994.

Mollie H. Beattie,

Director, Fish and Wildlife Service.

[FR Doc. 94-2303 Filed 2-1-94; 8:45 am]

BILLING CODE 4310-55-P