A Guide to the Amphibians
and Reptiles of California

Southern Mountain Yellow-legged Frog - Rana muscosa

Camp, 1917

(= Mountain Yellow-legged Frog - Rana muscosa)

Click on a picture for a larger view

Description • Taxonomy • Species Description • Scientific Name • Alt. Names • Similar Herps • References • Conservation Status

Southern Mountain Yellow-legged Frog Habitat

Orange: historical range of this species in Calfironia
Rana muscosa - Southern Mountain Yellow-legged Frog

Red: Historic range of similar species
Rana sierrae - Sierra Nevada Yellow-legged Frog

Click on the map for a topographical view

Map with California County Names

Adult Southern Mountain Yellow-legged Frogs from Mountains of Southern California

Adult, San Gabriel Mountains,
Los Angeles County

Adult, underwater, San Gabriel Mountains, Los Angeles County

Adult, San Gabriel Mountains,
Los Angeles County

Adult, Mt. San Jacinto,
Riverside County@ 2005 Brian Hubbs

Adult frogs, from San Bernardino Mountains stock, part of the captive breeding program at the San Diego Zoo's
Center for Conservation and Research for Endangered Species, courtesy of Jeffrey M. Lemm. Photos © Gary Nafis

Adult frogs, part of the captive breeding program at the San Diego Zoo's Center for Conservation and Research for Endangered Species, courtesy of Jeffrey M. Lemm. Photos © Gary Nafis

Adult, San Gabriel Mountains,
Los Angeles County

Juveniles

Juvenile, San Gabriel Mountains,
Los Angeles County

Juveniles, San Gabriel Mountains,
Los Angeles County

Juvenile, San Gabriel Mountains,
Los Angeles County

Juvenile, raised in captivity, part of the captive breeding program at the San Diego Zoo's Center for Conservation and Research for Endangered Species, courtesy of Jeffrey M. Lemm.
© Gary Nafis

Southern Mountain Yellow-legged Frogs from the Sierra Nevada Mountains

Adult, Tulare County
© Isaac Chellman

Adult, Tulare County
© Max Roberts

Adult, Tulare County
© Isaac Chellman

Adult, Tulare County
© Isaac Chellman

Adult with heavy spotting, Southern Sierra Nevada Mountains
© Max Roberts

Several adult Rana muscosa on a rock in a stream in the Southern Sierra Nevada Mountains. © Max Roberts

Adult Mountain Gartersnake eating a juvenile Southern Mountain Yellow-legged Frog in Tulare County
© Max Roberts

Reproduction, Eggs, and Tadpoles

Southern Mountain Yellow-legged Frog eggs

Pair of amplexing adults, part of the captive breeding program at the San Diego Zoo's Center for Conservation and Research for Endangered Species, courtesy of Jeffrey M. Lemm.
© Gary Nafis

Amplexing adults, part of the captive breeding program at the San Diego Zoo's Center for Conservation and Research for Endangered Species.
© Jeffrey M. Lemm

Pair of adults in amplexus,
Tulare County © Isaac Chellman

Eggs, close-up, part of the captive breeding program at the San Diego Zoo's Center for Conservation and Research for Endangered Species.
© Jeffrey M. Lemm

Adult and tadpole, San Gabriel Mountains, Los Angeles County
© Chris DeGroof

Immature tadpole, San Gabriel Mountains, Los Angeles County
© Chris DeGroof

Transforming tadpole underwater, San Gabriel Mountains, Los Angeles County

Habitat

Habitat, 5,100 ft., San Gabriel Mountains, Los Angeles County

Habitat, 5,200 ft., San Gabriel Mountains, Los Angeles County

Habitat, 5,000 ft., San Gabriel Mountains, Los Angeles County

Habitat, San Gabriel Mountains, Los Angeles County © William Flaxington

Habitat, 5,100 ft., San Gabriel Mountains, Los Angeles County

Habitat, 5,600 ft., Mt. San Jacinto, Riverside County

Habitat, Mt. San Jacinto,
Riverside County

Habitat, 5,300 ft., San Gabriel Mountains, Los Angeles County

Rana muscosa once inhabited
this area high up Mt. Palomar in
San Diego County

Adults in habitat, Tulare County
© Isaac Chellman

Adult in habitat, Fresno County
© Isaac Chellman

Southern Mountain Yellow-legged Frog Sign

National Forest Service signs detailing the attempt to protect a small struggling population of Southern
California Mountain Yellow-legged Frogs on Mt. San Jacinto, Riverside County

Short Videos

Some of the few last remaining juvenile and adult Southern Mountain Yellow-legged Frogs in a small creek on a sunny summer day in the San Gabriel Mountains.

Description

Size

Adults are moderate in size, 2 - 3 inches long from snout to vent (5 - 7.6 cm). (Stebbins & McGinnis, 2012)

Appearance

A medium-sized frog with a slim waist, long legs, smooth skin and webbing on the hind feet.
Ridges on the sides (dorsolateral folds) are not distinct.

Similar Species

Differs from Rana muscosa by having relatively shorter legs and a significantly different mating call.
When it is extended forward, the heel of the hind foot of Rana sierrae usually does not reach the nostril. The heel of Rana muscosa does reach the nostril.

Color and Pattern

Variable in color - olive, yellowish or brown above, with varying amounts of black or brown markings.
Pale orange to yellow below and underneath the hind legs.
No dark face mask is present.

Larvae (Tadpoles)

Tadpoles grow up to 2 inches in length (5 cm.)
Coloring is brown with a tint of gold and dark spots.

Comparing Red-legged Frogs and Yellow-legged Frogs and Bullfrogs

Life History and Behavior

Activity

A mountain frog of high elevations.
Chiefly diurnal.
Usually found close to water, typically within a couple of meters.
Rarely occurs where predatory fishes have been introduced.
Probably spends the winter at the bottom of frozen lakes.
Emerges shortly after snow melts.
In years of heavy snow, may only be active for about 3 months.

Smells like garlic when handled.

Longevity

Not known.

Voice

This frog makeis a short and rasping call often accellerated and rising at the end, sometimes preceeded by calls that don't rise at the end. Calls primarily underwater during the day, but may also call at night. This frog has no vocal sacs so the sound produced is fairly quiet. (You can listen to it online at the Western Soundscape Archive, and on the Lang Elliot and the Carlos Davidson CDs listed below in References.)

Diet and Feeding

Eats a variety of terrestrial and aquatic invertebrates, including beetles, ants, bees, wasps, flies, and dragonflies.
Tadpoles may also be consumed.

Frogs tend to sit and wait until they see prey come within range, then they strike, or creep up a little then strike, using their large sticky tongue to catch the prey and bring it into the mouth.

Reproduction

Reproduction is aquatic.
Fertilization is external, with the male grasping the back of the female and releasing sperm as the female lays her eggs.

Mating and egg-laying occurs after high creek waters have subsided, from March - May in the southern California populations.
In the southern Sierra Nevada populations, breeding may occur later after the snows melt from May to July.

Eggs

A cluster of eggs is laid in shallow water and is left unattached in still waters, but may be attached to vegetation in streams.

Tadpoles and Young

There is no information on the larval stage of Southern California populations, but it's possible they could transform their first year.
Tadpoles in the Sierra Nevada may overwinter, possibly taking as many as 3 or 4 summers before they transform.

Habitat

Inhabits lakes, ponds, meadow streams, isolated pools, sunny riverbanks in the southern Sierra Nevada Mountians.
In the mountains of southern California, inhabits rocky streams in narrow canyons and in the chaparral belt.
"...frequents streams that range from rocky, steep drainages to those with a gentle gradient, marshy margins, and sod banks. Large clear pools up to three feet deep are especially favored." (Stebbins & McGinnis 2012)

Geographical Range

No longer found in much of its former habitat. Historically Rana muscosa ranged
"...from Palomar Mountain in San Diego County through the San Jacinto, San Bernardino and San Gabriel Mountains of Riverside, San Bernardino and Los Angeles counties in southern California. These formed four isolated clusters of montane populations. In addition, the species occurred as an isolated cluster of populations on Breckenridge Mountain, south of the Kern River in Kern County, and in the Sierra Nevada in Tulare, Inyo and Fresno counties, extending north to Mather Pass. The distribution of R. muscosa in the Sierra Nevada is bordered by the crest of Sierra Nevada. No populations occur east of the crest. The mountain ridges that separate the headwaters of the South Fork Kings River from the Middle Fork Kings River, from Mather Pass to the Monarch Divide, form the northern border of the range. ... Rana muscosa is extinct on Palomar and Breckenridge mountains."
(Vredenburg, et al, 2007.)

Elevational Range

From 984 ft. - over 12,000 ft. elevation (370 - 3,660 m.)

Notes on Taxonomy

According to a February, 2008 petition by the Center for Biological Diversity and Pacific Rivers Council to list the Sierra Nevada Mountain Yellow-legged Frog as an Endangered Species, "The mountain yellow-legged frog in the Sierra Nevada is geographically, morphologically and genetically distinct from mountain yellow legged frogs in southern California. It is undisputedly a 'species' under the ESAOs listing criteria and warrants recognition as such."

Vredenburg, V. T., R. Bingham, R. Knapp, J. A. T. Morgan, C. Moritz & D. Wake (2007. Journal of Zoology 271: 361–374) have determined that this taxon consists of two species, which they name Rana muscosa - Sierra Madre Yellow-legged Frog, and Rana sierrae - Sierra Nevada Yellow-legged Frog. More from the CNAH.

In 2008, the Society for the Study of Amphibians and Reptiles recognized two species, Rana muscosa - Southern Mountain Yellow-legged Frog , and Rana sierrae - Sierra Nevada Yellow-legged Frog.

Alternate and Previous Names (Synonyms)

Rana muscosa - Mountain Yellow-legged Frog (Stebbins 1966, 1985, 2003)
Rana boylii muscosa (Stebbins 1954)
Rana boylii muscosa - Sierra Madre Yellow-legged Frog (Southern Yellow-legged Frog) (Wright & Wright 1949)
Rana boylii muscosa - Sierra Madre Yellow-legged Frog (Storer 1925)
Rana boylii muscosa - Sierra Madre Yellow-legged Frog (Grinnell and Camp 1917)

Conservation Issues (Conservation Status)

Endangered in Southern California and the southern Sierra Nevada Mountains, where it is absent from most of its historic range. Once thought to be extinct in the San Bernardino Mountains until a small population was discovered. Considered extinct on Breckenridge Mountain and Mt. Palomar. Only a few creeks have been found with frogs in the San Gabriel, San Bernardino, and San Jacinto mountains. This decline has been attributed to many factors, including bullfrogs, introduced non-native trout, airborne pollution, cattle grazing, ozone depletion, mining pollution, off road vehicle disturbance, public dumping, chytrid fungus, fires, and excessive flooding.

In June, 2009, biologists from the U.S. Geological Survey and scientists from the San Diego Natural History Museum retraced a 1908 expedition through the San Jacinto Wilderness near Idyllwild and re-discovered a population of frogs in two creeks 2.5 miles apart.

The San Diego Zoo, along with the California Dept. of Fish and Game, the U.S. Fish and Wildlife Service, the U. S. Forest Service, and the U.S. Geological Survey, has developed a Mountain Yellow-legged Frog Recovery Program, a captive breeding and translocation plan for the only remaining frogs known from the San Bernardino Mountains. In August of 2006, 75 tadpoles were removed from a drying creek bed in the San Bernardino Mountains and transferred to the program. They began planting eggs into the wild in April 2010.

Drought and wildfires threaten the endangered mountain yellow-legged frog. (Los Angeles Times, 8/20/16)

In August, 2016, the U.S. Fish and Wildlife Service announced the designation of 1.8 million acres of protected critical habitat in the Sierra Nevada mountains for Rana sierrae, the Sierra Nevada Yellow-legged Frog, the northern population of Rana muscosa, the Southern Mountain Yellow-legged Frog, and Anaxyrus canorus, the Yosemite Toad. BiologicalDiversity.org

Taxonomy
Family	Ranidae	True Frogs	Rafinesque, 1814
Genus	Rana	True Frogs	Linnaeus, 1758
Species	muscosa	Southern Mountain Yellow-legged Frog	Camp, 1917
Original Description
Camp, 1917 - Univ. California Publ. Zool., Vol. 17, No. 9, p. 118 from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
Meaning of the Scientific Name
Rana - Frog - "Rana" probably mimics how the Romans heard their call. muscosa - Latin - mossy, full of moss- referring to the lichen-like dark dorsal patches from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
Related or Similar California Frogs
Rana aurora Rana boylii Rana cascadae Lithobates catesbeiana Rana draytonii Lithobates pipiens Rana pretiosa Rana sierrae Lithobates yavapaiensis
More Information and References
California Department of Fish and Wildlife AmphibiaWeb Center for Biological Diversity Dr. Roland Knapp's site Rescuing a Dying Breed - Saving the Southern California Mountain Yellow-legged Frog The Mountain Yellow-legged Frog - Can They Be Saved? Stebbins, Robert C., and McGinnis, Samuel M. Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012. Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972. Flaxington, William C. Amphibians and Reptiles of California: Field Observations, Distribution, and Natural History. Fieldnotes Press, Anaheim, California, 2021. Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018. Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003. Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992. Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998. Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Amphibians of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009. Elliott, Lang, Carl Gerhardt, and Carlos Davidson. Frogs and Toads of North America, a Comprehensive Guide to their Identification, Behavior, and Calls. Houghton Mifflin Harcourt, 2009. Lannoo, Michael (Editor). Amphibian Declines: The Conservation Status of United States Species. University of California Press, June 2005. Storer, Tracy I. A Synopsis of the Amphibia of California. University of California Press Berkeley, California 1925. Wright, Albert Hazen and Anna Wright. Handbook of Frogs and Toads of the United States and Canada. Cornell University Press, 1949. Basey, Harold E. Discovering Sierra Reptiles and Amphibians. Yosemite Association and Sequoia Natural History Association, 1976, 1991. Davidson, Carlos. Booklet to the CD Frog and Toad Calls of the Pacific Coast - Vanishing Voices. Cornell Laboratory of Ornithology, 1995. Lang Elliott, Carl Gerhardt, and Carlos Davidson - The Frogs and Toads of North America - Houghton Mifflin Harcourt. 2009. Vredenburg, V. T., R. Bingham, R. Knapp, J. A. T. Morgan, C. Moritz & D. Wake (2007. Journal of Zoology 271: 361–374) Joseph Grinnell and Charles Lewis Camp. A Distributional List of the Amphibians and Reptiles of California. University of California Publications in Zoology Vol. 17, No. 10, pp. 127-208. July 11, 1917.

Conservation Status

The following conservation status listings for this animal are taken from the January 2024 State of California Special Animals List and the January 2024 Federally Listed Endangered and Threatened Animals of California list (unless indicated otherwise below.) Both lists are produced by multiple agencies every year, and sometimes more than once per year, so the conservation status listing information found below might not be from the most recent lists. To make sure you are seeing the most recent listings, go to this California Department of Fish and Wildlife web page where you can search for and download both lists:
https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals.

A detailed explanation of the meaning of the status listing symbols can be found at the beginning of the two lists. For quick reference, I have included them on my Special Status Information page.

If no status is listed here, the animal is not included on either list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status you can also go to the NatureServe and IUCN websites to check their rankings.

Special Animals List Notes:

Both federally recognized Distinct Population Segments (DPS) of the mountain yellow-legged frog (Rana muscosa) are currently Endangered (2021).
The mountain yellow-legged frog – northern DPS is known from the southern Sierra Nevada;
the mountain yellow-legged frog – southern DPS is known from the Transverse Ranges.

Endangered and Threatened Animals List Notes:

Though the scientific name Rana muscosa is not disputed, the State uses this common name, whereas the USFWS listing refers to two distinct population segments. This species is also known by the common name Sierra Madre yellow-legged frog (Vredenburg et al. 2007).

Organization

Status Listing

Notes

NatureServe Global Ranking

Critically Imperiled.

NatureServe State Ranking

Critically imperiled

U.S. Endangered Species Act (ESA)

Two separate populations are listed as Federally Endangered

Southern California DPS (San Gabriel, San Jacinto, and San Bernardino Mountains only)
Endangered -8/1/2002

Northern California DPS (North of the Tehachapi Mountains from the Monarch Divide to portions of the Kern River drainage.)
Endangered - 6/30/2014

California Endangered Species Act (CESA)

Listed as Endangered 4/1/2013

California Department of Fish and Wildlife

Watch List

Bureau of Land Management

None

USDA Forest Service

Sensitive

IUCN

Endangered

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