Sierra Nevada Mountain Yellow-Legged Frog (Rana sierrae and Rana muscosa)

Threats

Sierra Nevada Mountain Yellow-Legged Frog Once the most abundant frog in the Sierra Nevada, the mountain yellow-legged frog is now critically endangered in the Range of Light. Populations of mountain yellow-legged frogs have declined dramatically and they are now found in fewer than 7 percent of their historic localities. This decline is due to a number of factors, including the stocking of fish in high elevation lakes, many of which did not contain fish historically. As a result of these fish stocking efforts, which continue today, more than 90% of Sierra Nevada lakes which were naturally fish-less now contain introduced trout. There is abundant scientific evidence that predation by non-native trout on mountain yellow-legged frog tadpoles, as well as adults, is a major factor in the decline of this amphibian. Other factors leading to declines in population include toxins from pesticides and herbicides, livestock impacts, chytrid fungal infection, and off-highway vehicle (OHV) recreation.

Habitat

The habitat of the mountain yellow-legged frog consists of glaciated lakes, ponds, tarns, springs, and streams in the upper elevations (above 6,000 feet generally) of the Sierra Nevada. The adaptations that allow them to live at these high elevations and cold temperatures have made them highly vulnerable to introduced fish species. The species is usually associated with montane riparian habitats in lodgepole pine, yellow pine, sugar pine, white fir, whitebark pine, and wet meadow vegetation types, and range from southern Plumas County to southern Tulare County.

Conservation

Nearly all the remaining populations of mountain yellow-legged frog occur on public lands, and studies have demonstrated that in the absence of disease, it is possible to bring these species back to recovery. Recent surveys, however, have shown an increase in the deadly disease, chytridiomycosis. The Sierra Nevada Framework Plan provides strategies to reduce all the factors causing a decline in mountain yellow-legged frog populations including prohibition of pesticides from frog habitat, removing livestock near lakes and pond areas, prohibiting development of new recreation trails that would affect known frog sites, and the identification of Critical Aquatic Refuges to protect sensitive species. It also calls for the removal of exotic fish from frog habitat. The 2004 revisions to the Framework have weakened the protections for the mountain yellow-legged frog by failing to maintain grazing restrictions for amphibian species in key habitats. A return to a robust monitoring and restoration program as promoted and required by the original Sierra Nevada Framework is vital to protect the species from disappearing from the Sierra Nevada altogether.

Status

Until recently, the mountain yellow-legged frog in the northern and central Sierra Nevada, and those in the mountains of southern California, were thought to be the same species. Today the Sierra Nevada mountain yellow-legged frog--specifically, those frogs north of Mather Pass--is recognized as a unique species, Rana sierrae. The species are thought to have diverged more than 2 million years ago. Both species are critically endangered with extinction. Surveys have shown that 93% of the R. sierrae and 95% of R. muscosa historical populations are now extinct.

In 2003 the U.S. Fish and Wildlife Service (USFWS) determined that the Sierra Nevada population of the mountain yellow-legged frog should be protected under the Endangered Species Act, but that listing the species under the Act is "warranted but precluded" by the agency's backload of priorities and budget constraints. Subsequent legal action on behalf of the species resulted in a 2007 USFWS 12-month petition finding (see below, in Supporting Documents) that the mountain yellow-legged frog is still precluded from listing under the Endangered Species Act, basically due to the agency's lack of funds and priority allocation. This continued inaction through administrative delay is pushing the species closer to extinction throughout the Sierra Nevada.

For more information about the mountain yellow-legged frog, visit the mountain yellow-legged frog website of Dr. Roland Knapp, at http://www.mylfrog.info.