Rana muscosa

Mountain yellow-legged frog [Northern California DPS]

Family: Ranidae · Class: Amphibia · Order: Anura

Conservation status: (SE) · Endangered · G1 S2

The mountain yellow-legged frog (Rana muscosa) Northern California Distinct Population Segment is a medium-sized ranid frog endemic to high-elevation aquatic habitats in the Sierra Nevada. Adults typically measure 40 to 95 mm (1.6 to 3.7 inches) in snout-vent length, with females generally larger than males. The dorsal surface ranges from yellow to brown or olive, often with dark irregular spots or blotches. The characteristic yellow coloration is most prominent on the underside of the hind legs and lower abdomen, giving the species its common name. The skin is smooth to slightly granular, and males develop enlarged thumbs and darkened throat patches during breeding season. According to the SummitWest Environmental Database, the Northern California DPS occurs north of the Tehachapi Mountains from the Monarch Divide to portions of the Kern River drainage. This population is geographically isolated from the Southern California DPS and historically occupied high-elevation lakes, ponds, and streams throughout the central and northern Sierra Nevada. Current distribution is severely fragmented, with remaining populations concentrated in specific watersheds including portions of Kings Canyon and Sequoia National Parks. Mountain yellow-legged frogs inhabit montane aquatic ecosystems at elevations typically ranging from 1,200 to 3,650 meters (4,000 to 12,000 feet). The species requires permanent or near-permanent water bodies including alpine lakes, tarns, ponds, and slow-moving stream reaches. Adults are closely associated with rocky shorelines and submerged boulders that provide basking sites and cover. Tadpoles require shallow, sun-exposed areas with minimal flow for development, which can extend 2 to 4 years at high elevations due to short growing seasons. Breeding occurs from April through August, depending on elevation and snowmelt timing. Females deposit 100 to 350 eggs in shallow water, typically attached to vegetation or rocks. The extended larval period is an adaptation to harsh montane conditions, with tadpoles overwintering under ice for multiple years before metamorphosis. Adults are primarily aquatic, rarely moving more than 100 meters from water. Diet consists of terrestrial and aquatic invertebrates including flies, beetles, spiders, and aquatic larvae. The U.S. Fish and Wildlife Service listed the Northern California DPS as endangered in 2014, with the state of California providing endangered status protection. Population declines exceed 90% across the historical range, with fewer than 200 known occupied sites remaining. Primary threats include the introduced pathogenic fungus Batrachochytrium dendrobatidis (Bd), which causes chytridiomycosis and has caused widespread population extirpations. Non-native trout predation on tadpoles and juveniles represents another significant threat, as high-elevation lakes were historically fishless. Additional threats include habitat alteration from grazing, recreational activities, and climate change effects on snowpack and hydroperiod. Recovery efforts focus on Bd research, fish removal from critical habitats, captive breeding programs, and population monitoring.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.