Overview
The California red-legged frog is the largest native frog in the western United States. Named for its red abdomen and hind legs, the frog was once found in 46 counties stretching from southern Mendocino County, California, inland to Shasta County, California and south to Baja California, Mexico.
Habitat loss and alteration, as well as non-native species, are the primary factors that have negatively impacted the California red-legged frog throughout its range. In the Central Valley of California, more than 90% of historic wetlands have been diked, drained or filled, primarily for agricultural development and secondarily for urban development. The frog was listed as threatened in 1996.
Scientific Name
Identification Numbers
Characteristics
Behavior
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.
Life Cycle
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.
Physical Characteristics
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.
Similar Species
Habitat
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.
Land on which the natural dominant plant forms are grasses and forbs.
A dense growth of trees and underbrush covering a large tract.
The land near a shore.
A considerable inland body of standing water.
A landmass that projects conspicuously above its surroundings and is higher than a hill.
A natural body of running water.
Of or relating to cities and the people who live in them.
Environments influenced by humans in a less substantial way than cities. This can include agriculture, silvaculture, aquaculture, etc.
Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.
Food
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).
Geography
Today, the frog is known to occur in 35 counties in California extending along the California Coast Range from southern Mendocino County to Santa Barbara County, through the northern Transverse Ranges from Santa Barbara County to Los Angeles County, and in isolated populations in the Sierra Nevada foothills, Riverside County, and San Diego County. The California red-legged frog is no longer found in the Central Valley of California, but is still common in the San Francisco Bay Area and along the Central Coast of California. Additional populations are found in Baja California, Mexico.
Timeline
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