Q. What is the mountain yellow-legged
frog?
The mountain yellow-legged frog (Rana muscosa), a member of the family of ‘true
frogs', (Ranidae) is a relatively small frog that measures about 1.5 to three
inches in length from the snout to the base of the backbone. Mountain yellow-legged
frogs have highly variable skin patterns and coloration ranging from large,
discrete dark spots to numerous, smaller spots; coloration may be a mix of brown
or yellow, but can often include hues of gray, red, or greenish-brown. Female
mountain yellow-legged frogs are slightly larger than males. Mountain yellow-legged
frogs are diurnal (active both day and night), highly aquatic frogs that feed
on terrestrial and aquatic insects including beetles, bees, dragonflies, and
ants.
Q. What is a ‘true frog'?
The ‘true frog' family includes one genus, Rana, found in North America.
This genus is comprised of 21 species including the mountain yellow-legged frog.
True frogs are, as the name implies, truly amphibious. Species in this genus
typically living along the edge of water and rely heavily on an aquatic environment
for foraging, shelter, breeding, and protection from predators. True frogs are
carnivorous and feed primarily on insects, spiders, and crustaceans, but they
will eat just about anything else that can be caught and swallowed.
Q. Why is the southern California
population considered a Distinct Vertebrate Population Segment?
Research indicates there are two major ‘clades' (a group of organisms sharing
a common ancestor) of mountain yellow-legged frog, divided into four subgroups
- northern Sierra Nevada, central Sierra Nevada, southern Sierra Nevada, and
southern California. The northern ‘clade' includes mountain yellow-legged
frogs in the Northern and Central Sierra Nevada Mountains; the southern ‘clade'
includes frogs from the southern Sierra Nevada and southern California mountains.
Genetic analyses indicate that mountain yellow-legged frogs in southern California
are significantly different from those inhabiting the Sierra Nevada, including
those from the southern Sierra Nevada. Mountain yellow-legged frogs in southern
California currently inhabit portions of the San Gabriel, San Bernardino, and
San Jacinto Mountains in Los Angeles, Riverside, and San Bernardino counties.
Three elements are used to determine if a vertebrate population may be considered a distinct population segment: 1) discreteness of the population segment in relation to the remainder of the species to which it belongs; 2) significance of the population segment to the species to which it belongs; and 3) the population segment's conservation status in relation to the Endangered Species Act's (Act) standards for listing?
Mountain yellow-legged frogs in southern California and those in the Sierra Nevada Mountains are geographically separate and are genetically different. The U.S. Fish and Wildlife Service (Service) has determined the southern California population of mountain yellow-legged frog meets the criteria of a distinct vertebrate population segment (DPS). Mountain yellow-legged frogs in southern California represent the southernmost occurrence of the species and extinction of this DPS would substantially reduce the overall range of the species and could have potential impacts to its long-term survival.
Q. When was this DPS proposed
for listing under the Act, and Why?
In 1995, the Service was petitioned by D.C. "Jasper" Carlton (of the
Biodiversity Legal Foundation), and Bonnie M. Dombrowski and Michael C. Long
(individuals), to list the southern California population of mountain yellow-legged
frog as endangered pursuant to the Act. On July 8, 1997, we published a 90-day
administrative finding in the Federal Register indicating the petition contained
substantial information and that listing of the species under the Act may be
warranted. Following the publication of our 90-day finding, we initiated a 12-month
status review.
On December 22, 1999, we published a proposed rule to list the southern California DPS of mountain yellow-legged frog as endangered under the Act. Populations of mountain yellow-legged frogs in southern California have declined significantly over the past 30-40 years. Although the exact causes of this rapid decline may not be fully understood, the small number of remaining populations in southern California are threatened by impacts from human-related activities that occur adjacent to and within areas inhabited by the frogs; random genetic, demographic, and environmental effects (e.g., fire, extreme drought, loss of genetic vigor resulting from inbreeding); and may also be threatened by predation from non-native trout and bullfrogs, and disease (e.g., ‘Red-leg' disease, chytrid fungus).
Q. What is ‘red-leg' disease?
Red-leg disease is caused by a bacterium, Aeromonas hydrophila. Frogs infected
with this disease may be lethargic, and be unable to remain upright; red spots
and swollen skin may also develop. In the Sierra Nevada, the loss of a population
of mountain yellow-legged frog was thought to be caused by ‘red-leg' disease,
and there are studies reporting deaths of boreal toads in the Rocky Mountains
due to this disease. It is not clear what role ‘red-leg' disease or other
viruses may play in the decline of amphibians, including the mountain yellow-legged
frog.
Q. What is chytrid fungus?
Another pathogen causing concern is chytrid fungus (Batrachochytrium dendrobatidis).
This naturally occurring, freshwater fungus was discovered in the mid-1990s
and has been linked to the mortality of many amphibian species in the United
States, Australia, and Central America. The chytrid fungus attacks the mouthparts
of tadpoles and impairs their ability to feed. Chytrid fungus was discovered
in mountain yellow-legged frog larvae in the Sierra Nevada, but has not yet
been seen in the southern California DPS of mountain yellow-legged frog.
Q. Why are amphibians considered
indicators of aquatic ecosystem health?
Many species of amphibians spend most of their lives in water and breathe at
least partially through their skin making them highly sensitive to changes in
their aquatic environments. Worldwide many species of amphibians including frogs,
toads, and salamanders are declining. Scientists are working hard to find answers
as to why many amphibian species are declining, even those that live in areas
relatively untouched by humans. In California, several species are already listed
under the Act, including the threatened California red-legged frog (Rana aurora
draytonii) and the endangered arroyo toad (Bufo californicus).
Q. Are other populations of mountain
yellow-legged frog declining?
Yes. In October 2000, the Service published a 90-day administrative finding
on a petition to list the Sierra Nevada populations of mountain yellow-legged
frog as endangered pursuant to the Act. The Service concluded that the petition
provided substantial information and that listing of the Sierra Nevada populations
of mountain yellow-legged frog under the Act may be warranted. A 12-month status
review was initiated.
Q. Was the public provided with
an opportunity to comment on the proposed listing of the southern California
DPS of mountain yellow-legged frog?
Yes. At the time we published our proposal to list the southern California DPS
of mountain yellow-legged frog under the Act, we opened a 60-day public comment
period seeking information on the biological, commercial trade, or other relevant
data concerning threats to the species; distribution of native rainbow trout
in the mountains of the southern California prior to the stocking programs of
the California Department of Fish and Game; locations of any additional populations
of this species in southern California; and current or planned activities in
the southern California mountains where mountain yellow-legged frogs occur and
the possible impacts of these activities on this DPS of mountain yellow-legged
frog.
Following a request from the California Department of Fish and Game, we reopened an additional 30-day comment period from May 19, 2000, to June 19, 2000.
The final determination to list the southern California DPS of mountain yellow-legged frog is based upon the best scientific and commercial information available and incorporates comments and information received on the proposal.
Q. How will listing of this DPS
affect public use within Angeles and San Bernardino National Forests?
The southern California DPS of mountain yellow-legged frog occurs in only a
few small, isolated populations in portions of the San Gabriel, San Bernardino,
and San Jacinto Mountains. The stream reaches inhabited by the species are almost
wholly contained within the boundaries of the U.S. Forest Service's Angeles
National Forest (ANF) and San Bernardino National Forest (SBNF); some portion
of habitat used by the species may be found on private inholdings within SBNF.
The four southern California National Forests (Los Padres National Forest, Cleveland National Forest, ANF, and SBNF) revised their Land and Resource Management Plans (LRMP) and initiated consultation with the Service pursuant to section 7 of the Act in 2000. In February 2001, the Service issued a biological opinion on the LRMPs and the effects of activities within the National Forests on 59 federally listed species and critical habitat for 10 species; a conference opinion was issued for the proposed endangered southern DPS of mountain yellow-legged frog and proposed critical habitat for four species.
Within the San Gabriel Mountains (ANF) there are no roads or developed recreation sites in mountain yellow-legged frog habitat and only nine acres are affected by trails; in the San Bernardino Mountains (SBNF) there are seven acres of trails and nine acres of roads within the species' habitat; and in the San Jacinto Mountains (SBNF) approximately 40 acres of habitat are potentially affected by developed recreation sites, 11 acres are affected by roads, and only one acre is affected by trails.
Both ANF and SBNF have proposed undertaking actions to help conserve the remaining populations of the southern California DPS of mountain yellow-legged frog, including: 1) installing signs to encourage the public to remain on designated trails in areas inhabited by the species; 2) developing mountain yellow-legged frog educational workshops for organizational camp permittees; 3) removing campgrounds or their components (barbeque pits, picnic tables) in areas adjacent to streams inhabited by the species; 4) using additional patrols to prevent illegal suction dredge mining in the East Fork San Gabriel River, upstream from the Sheep Mountain Wilderness Area boundary; 5) rerouting a portion of a trail in Little Rock Canyon; 6) acquiring mountain yellow-legged frog habitat from private inholdings; and 7) preventing the depositing or stockpiling of brush, loose soils or other debris along or within stream reaches occupied by the species.
Q. How will listing of the southern
California DPS of mountain yellow-legged frog affect recreational fishing?
Research conducted within the Sierra Nevada has shown a clear link between the
introduction of trout into previously fishless lakes and a decline in populations
of mountain yellow-legged frog. The possible impacts of the introduction of
non-resident trout in southern California streams inhabited by mountain yellow-legged
frogs is not clearly understood.
The California Department of Fish and Game intends to: 1) suspend trout stocking indefinitely at Dark Canyon along the North Fork, San Jacinto River (SBNF); 2) suspend stocking activities and evaluate results on mountain yellow-legged frog populations at three locations - Fuller Mill Creek and Mill Creek (SBNF), and North Fork San Gabriel River (ANF); and 3) continue to stock trout and conduct surveys for mountain yellow-legged frogs at six other locations where the species is believed to no longer exist or where physical barriers separate trout from a population of mountain yellow-legged frogs - East and West Forks San Gabriel River, Arroyo Seco Creek, Upper and Lower Tujunga (ANF), and Lake Fullmer/Hall Canyon (SBNF).
Q. Is the Service proposing to
designate critical habitat for the southern California DPS of mountain yellow-legged
frog?
Not at this time. Although the Service has determined that designation of critical
habitat for the southern California DPS of mountain yellow-legged frog is prudent,
we are not proposing to designate critical habitat at this time. The deferral
of the critical habitat designation for this DPS of mountain yellow-legged frog
will allow us to concentrate our limited resources on higher priority critical
habitat designations, and other listing actions. We will prepare a proposal
for critical habitat designation for this species in the future when our available
resources allow it.
Even without the designation of critical habitat, section 9 of the Act prohibits any person subject to the jurisdiction of the United States to ‘take' (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.
Activities identified by the Service that may result in a violation of section 9 of the Act include, but are not limited to: 1) ‘Take' of southern California DPS of mountain yellow-legged frogs without a permit; 2) possessing, selling, delivering, transporting, or shipping them illegally; 3) interstate of foreign commerce and import/export of mountain yellow-legged frogs; 4) introduction of non-native species that compete or hybridize with, or prey on, mountain yellow-legged frogs; 5) destruction of alteration of habitat by suction dredging, channelization, diversion, in-stream vehicle operation or rock removal, or other activities that result in the destruction of significant degradation of cover, channel stability, substrate composition, temperature, and habitat used by the southern California DPS for foraging, cover, migration, and breeding; and 6) discharging or dumping of toxic chemicals, silt, or other pollutants into waters supporting mountain yellow-legged frogs.
Prepared by: U.S. Fish and Wildlife
Service
Carlsbad Fish and Wildlife
Prepared on: July 2, 2002