This frog is a member of the mountain yellow-legged frog complex which is comprised of two species: Rana muscosa and Rana sierrae. Both species are highly aquatic and are always found within a meter or two from the edge of water. Rana sierrae is yellowish or reddish brown from above, with black or brown spots or lichen-like markings. Toe tips are usually dusky. Underside of hind legs and sometimes entire belly is yellow or slightly orange, usually more opaque than in foothill yellow-legged frog, Rana boylii. Yellow often extends forward to level of forelimbs. Dorsolateral folds present but frequently indistinct. The tadpoles are black or dark brown and are large (total length often exceeds 10 cm) and metamorphose in 1-4 years depending on the elevation. Rana sierrae differs from Rana muscosa in having relatively shorter legs. When a leg is folded against the body the tibio-tarsal joint typically falls short of the external nares. The mating call of R. sierrae is significantly different from that of R. muscosa in having transitions between pulsed and noted sounds. Both species call underwater. Males can be heard above water but only from a short distance away (<2 meters). The two species also differ in mitochondrial DNA. The mitochondrial DNA, male advertisement calls, and morphology datasets are geographically concordant (Vredenburg et al. 2007).