Sierra Nevada Yellow-legged Frog

The Sierra Nevada yellow-legged frog is one of two species (along with the southern mountain yellow-legged frog, Rana muscosa) that make up the "mountain yellow-legged frog species complex." The Sierra Nevada yellow-legged frog is very similar in appearance to the southern mountain yellow-legged frog. The two were separated into different species by examining mitochondrial DNA, and subtle differences in morphology and breeding calls. R. sierrae is highly aquatic and normally found within a few meters of water.

The frogs are often olive, brownish, or yellowish above with varying amounts of black or brown markings, often with dark spots or bands. Yellow or light orange coloration can be present on much of the ventral side (including the chin), but the coloration is most often present on the underside of their legs, lower abdomen, groin, and sometimes up onto the flanks, although not all individuals possess distinct ventral yellow coloration.

Tadpoles of R. sierrae appear black or brown, and vary from around a centimeter soon after hatching, up to approximately 75 mm total length before metamorphosis, which may take several years in higher elevation populations. Females generally grow up to 3.4 inches (87 mm) snout vent length (SVL) and males grow up to about 2.7 inches (68 mm) SVL. R. …

R. sierrae inhabit lakes, ponds, streams, flooded meadows, and other wetland habitats, from about 4,500 feet up to 12,000 feet in elevation. The species spends most of its life in or around these water sources, which provide foraging, breeding, and overwintering habitat. The species is found primarily from Kings Canyon National Park and surrounding National Forest Lands up through Plumas County, in the northern Sierra Nevada. Although overall population densities for R. sierrae have declined when compared with historic distributions (particularly at the northern extent of the species' range), the species is showing positive signs of recovery in some locations.

Adults can be found basking on aquatic habitat features (rocks, logs, shorelines), resting near shore with their head protruding from shallow water, hiding (e.g., in crevices, beneath undercut banks, under overhanging logs, within low shoreline vegetation), or sitting on the bottom of lakes and streams. Larvae often congregate (sometimes in dense clusters within larger populations) in warm, shallow areas of water.

Breeding for R. sierrae typically starts soon after snowmelt in spring or early summer, but timing varies, depending on elevation, water year, and local conditions of the area (usually between April and August). During the breeding season, adult male frogs will call for a mate (usually within or underwater) and upon the arrival of a female, the male will grasp the female's back (in a position known as amplexus) and externally fertilize as the female releases eggs.

Eggs are laid in masses underwater, often attached to rocks, submerged vegetation, or beneath undercut banks. Eggs are typically laid in fishless habitats where water is deep enough to not freeze entirely overwinter. (Overwinter mortality, due to freezing of shallow habitats and anoxic conditions, has been reported.) Egg masses have been estimated to contain between 100 and 350 eggs. The eggs will then hatch in about 15–20 days.

Larvae will then develop into adult frogs over a period ranging from one to four years, depending on the elevation, weather, and local conditions.