The mountain yellow-legged frog (Rana muscosa), also known as the southern mountain yellow-legged frog, is a species of true frog endemic to California in the United States. It occurs in the San Jacinto Mountains, San Bernardino Mountains, and San Gabriel Mountains in Southern California and the Southern Sierra Nevada. It is a federally listed endangered species. Populations formerly classified as Rana muscosa in the northern Sierra Nevada have since been redescribed as a new species: Rana sierrae, the Sierra Nevada yellow-legged frog. The Sierra Nevada yellow-legged frog has also been classified as an endangered species since 2013. The mountains separating the headwaters of the South Fork and Middle Fork of the Kings River mark the boundary between the ranges of the two species. Description Rana muscosa is 4 to 8.9 centimeters long. Females tend to be larger than males. Its color and patterning are variable. It is yellowish, brownish, or olive with black and brown markings. The underside of its hind legs can be different hues of yellow, from a bold sun yellow to a lighter pale yellow; larger ones may can hints of orange on their hind legs. The throats of it range from white to yellow. Along with its variable coloration, the frog also has a dorsal pattern with dark spots in different shapes and sizes. Its species name muscosa is from the Latin meaning "mossy" or "full of moss", inspired by its coloration. It may have light orange or yellow thighs. When handled, the frog emits a defensive odor reminiscent of garlic. Habitat The frog occurs in mountain creeks, lakes and lakeshores, streams, and pools, preferring sunny areas. It rarely strays far from water, and can remain underwater for a very long time, likely through cutaneous gas exchange. As such, adults can be found on rocks around shorelines. Close proximity to water is important because eggs are either laid underwater attached to rocks or in shallow waters. The tadpoles require a permanent water habitat for at least two years while they develop. This is because tadpoles can die from a lack of moisture, especially dry summers. The frog has been noted at elevations of between about 1,214 and 7,546 feet (370 and 2,300 meters) in Southern California. These habitats are primarily found in north of California in Sierra Nevada and south of California in the Transverse ranges. Reproduction and early life The frog emerges from its wintering