Federal Register, Volume 59 Issue 22 (Wednesday, February 2, 1994)

[Federal Register Volume 59, Number 22 (Wednesday, February 2, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-2303]

[[Page Unknown]]

[Federal Register: February 2, 1994]

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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