California Red-legged Frog

Rana draytonii is a moderate to large (4.4–14 cm or 1.7–5.5 in) frog. It is the biggest native frog species in the western United States. The back is a brown, grey, olive, or reddish color, with black flecks and dark, irregular, light-centered blotches, and is coarsely granular. A dark mask with a whitish border occurs above the upper jaw, and black and red or yellow mottling is in the groin. The lower abdomen and the undersides of its hind legs are normally red. The male can be recognized by its large forelimbs, thumbs, and webbing. Only a portion of the toes are webbed, and it uses vocal sacs to grunt during the breeding season. The juvenile frog has more pronounced dorsal spotting, and may have yellow, instead of red, markings on the undersides of the hind legs. A characteristic feature of the red-legged frog is its dorsolateral fold, visible on both sides of the frog, extending roughly from the eye to the hip. R. draytonii looks very similar to the northern red-legged frog.

The California red-legged frog is found in California and extreme northern Baja California, northwestern Mexico. This species now occurs most commonly along the northern and southern Coast Ranges, and in isolated areas in the foothills of the Sierra Nevada mountains. The current southernmost California populations are on the Santa Rosa Plateau in Riverside County, and within the Upper Las Virgenes Canyon Open Space Preserve in the Simi Hills in eastern Ventura County, near the community of West Hills. In 2015, egg masses from the nearby Simi Hills were introduced to two streams in the Santa Monica Mountains. Juvenile frogs were found living at the locations a year later.

Rana draytonii has disappeared from an estimated 70% of its range, and is now only found in about 256 streams or drainages in 35 counties of California. However, the species is still common along the coast, and most of its population declines are in the Sierra Nevada and Southern California. The California red-legged frog is an important food source for the endangered San Francisco garter snake in San Mateo County. The California newt is often found with this species due to sharing habitat requirements and the newt's eating their eggs. The California red-legged frog primarily eats earthworms, beetles, flies, and other winged insects. There have been instances where the species was viewed as preying on juvenile snakes, small mammals such as mice, and other frogs and tadpoles. Breeding occurs from late December to early April. The male frog's advertisement call is a series of a few small grunts, usually given while swimming around underwater. Choruses are weak and easily missed. The adult California red-legged frog is nocturnal, while juvenile frogs are both nocturnal and active during the daytime. The species inhabits dense, shrubby, or emergent riparian vegetation and still or slow-moving perennial and ephemeral water bodies that also serve as breeding sites. This species has been noted to utilize upland habitats as adults near aquatic areas (such as creeks). …