Adult California red-legged frogs are largely nocturnal while juveniles are active both day and night. Frogs are inactive in cold or hot, dry temperatures in the late summer and winter months. They may be active all year in coastal areas where temperatures don’t fluctuate as much.  

California red-legged frogs live up to five years the wild, but few survive beyond two years.

Most male California red-legged frogs reach sexual maturity at 2 years and females at 3 years of age and are often prolific breeders. They lay their eggs during or shortly after large rainfall events in late winter and early spring between November through May. Each egg mass contains about 300 to 4,000 eggs, but fewer than 1% of eggs laid survive the tadpole phase.

The California red-legged frog is the largest native frog in the western United States. Adult females are larger than males at 5.4 inches (138 millimeters). Males reach 4.5 inches (116 millimeters). 

The California red-legged frog is a colorful amphibian. The abdomen and hind legs of adults are often red or salmon pink. The back of this species is characterized by small black flecks and larger irregular dark blotches, with indistinct outlines on a brown, gray, olive or reddish-brown background color.

The California red-legged frog spends the bulk of its life in or near water sources like streams or stock ponds, which the species uses for breeding. The frog moves into neighboring upland areas to feed and shelter when stream flow levels are high. In the summer, they seek relief from the heat by hiding under rocks or boulders, leaf litter, small stream channels or animal burrows.

California red-legged frog’s diet is highly variable. Tadpoles feed on algae by grazing on the surface of rocks and vegetation. Juvenile and adult frogs mostly eat insects and other invertebrates. As they get larger, they also eat small vertebrates, including Pacific tree frogs (Pseudacris regilla) and California mice (Peromyscus californicus).