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 of Rana muscosa in the northern Sierra Nevada have been redescribed as a new species, Rana sierrae, the Sierra Nevada yellow-legged frog. This has been proposed as an endangered species as of 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.
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Oviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
Jumping (saltation) can be distinguished from running, galloping, and other gaits where the entire body is temporarily airborne by the relatively l...
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starts withRana muscosa is 4 to 8.9 centimeters long. Its color and patterning are variable. It is yellowish, brownish, or olive with black and brown markings. 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.
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. The tadpoles require a permanent water habitat for at least two years while they develop. The frog has been noted at elevations of between about 1,214 and 7,546 feet (370 and 2,300 meters) in Southern California.
The frog emerges from its wintering site soon after snowmelt. Its breeding season begins once the highest meltwater flow is over, around March through May in the southern part of its range, and up to July in higher mountains to the north. Fertilization is external, and the egg cluster is secured to vegetation in a current, or in still waters sometimes left floating free. The juvenile may be a tadpole for 3 to 4 years before undergoing metamorphosis.
The frog lacks a vocal sac. Its call is raspy, rising at the end. During the day, it calls underwater.
This species feeds on insects such as beetles, ants, bees, wasps, flies, and dragonflies. It is also known to eat tadpoles.
The frog is an endangered species under the US Endangered Species Act. The International Union for Conservation of Nature has also listed it as endangered. Its NatureServe conservation status is Imperiled.
Once a common species, Rana muscosa was absent from much of its native range by the 1970s. Over the course of the last hundred years, 90% of its populations have been eliminated. The frog was known from 166 locations in the Southern California mountains, and as of 2007, only seven or eight remained. The 2009 discovery of R. muscosa at two locations in the San Bernardino National Forest was newsworthy. The frog is represented in the Sierra Nevada by three or four populations. Its decline is attributed to many factors, including introduced species of fish such as trout, livestock grazing, chytrid fungus, and probably pesticides, drought, and ultraviolet radiation.
The first successful captive breeding of the frog occurred in 2009 when three tadpoles were reared at the San Diego Zoo. Conservation workers at the zoo plan to release any more surviving captive-bred frogs in the San Jacinto Mountains, part of their native range.
In 2015 frogs and tadpoles of the species were reintroduced to Fuller Mill Creek in the San Bernardino Mountains and San Bernardino National Forest. They were bred and raised the Arnold and Mabel Beckman Center for Conservation Research in Escondido, one of the organizations that have partnered with the San Diego Zoo Institute for Conservation Research (ICR) to save the species from extinction. The Los Angeles Zoo is also a coalition partner and is raising two groups of wild collected tadpoles from two localities in the San Gabriel Mountains where they are released when ready.
In 2015, the Oakland Zoo began a rehabilitation project of the frog in order to fuel efforts to save the species. Every year, a group of tadpoles are taken from native lakes throughout California and brought to the zoo. There, the tadpoles are grown to juvenile frogs, while also undergoing an inoculation process to render them immune to the chytridiomycosis fungus disease. Once ready, the now chytrid immune juvenile frogs are released back into the lakes they were found. In 2016, the Oakland Zoo released 53 specimens into various lakes in Sequoia and Kings Canyon National Parks. The program is set to release 130 inoculated individuals into lakes in Sequoia and Kings Canyon National Parks and Inyo National Forest in 2017.
