California Red-Legged Frog
Photo Credit: Flo Gardipee/USFWS
Basic Species Information
Threatened. The species is likely to become endangered in the foreseeable future throughout all or a significant portion of its range, but they are not in danger of extinction right now.
The California red-legged frog is the largest native frog in the western United States. It ranges in size from 1.5 to 5 inches long (4 to 13 cm).
The abdomen and hind legs of adults are mostly red. The back has small black flecks and larger irregular dark blotches. These have indistinct outlines on a brown, gray, olive, or reddish background color. The spots on the frogs' backs usually have light centers. Lateral folds are prominent on the back.
Tadpoles (larvae) are from 0.6 to 3 inches (14 to 80 mm)long. They are dark brown and yellow, with darker spots.
The diet of California red-legged frogs is variable. Larvae probably eat algae. Invertebrates, such as insects, are the most common food items of adult frogs. Larger frogs frequently eat vertebrates, such as Pacific tree frogs and California mice.
Young frogs are active both during the day and at night, whereas adult frogs are largely nocturnal. Feeding likely occurs along the shoreline and on the surface of the water.
The California red-legged frog occupies a fairly distinct habitat, combining both specific water (aquatic) and upland (terrestrial) components. California red-legged frog habitat includes nearly any area within 1-2 miles of a breeding site that stays moist and cool through the summer; this includes non-breeding aquatic habitat in pools of slow-moving streams, perennial or ephemeral ponds, and upland sheltering habitat such as rocks, small mammal burrows, logs, densely vegetated areas, and even, man-made structures (i.e. culverts, livestock troughs, spring-boxes, abandoned sheds).
Breeding sites are generally found in deep, still or slow-moving water (greater than 2.5 feet) and can have a wide range of edge and emergent cover amounts. California red-legged frogs can breed at sites with dense shrubby riparian or emergent vegetation, such as cattails, tules, or overhanging willows or can proliferate in ponds devoid of emergent vegetation and any apparent vegetative cover (i.e., stock ponds).
California red-legged frogs enter a dormant state during summer or dry weather (estivate) in small mammal burrows and moist leaf litter. They have been found up to 100 feet from water in adjacent dense riparian vegetation.
Northern localities of California red-legged frogs breed in January to March, soon after the ice melts, while frogs in southern localities have earlier breeding records, November through March.
The species is endemic (native and restricted) to California and Baja California, Mexico, at elevations ranging from sea level to approximately 5,000 feet (1,500 meters). Records of the California red-legged frog are known from Riverside County to Mendocino County along the Coast Range; from Calaveras County to Butte County in the Sierra Nevada; and in Baja California, Mexico.
California red-legged frogs are still locally abundant within portions of the San Francisco Bay area (including Marin County) and the central coast.
Within the remaining distribution of the species, only isolated populations have been documented in the Sierra Nevada, northern Coast, and northern Transverse ranges.
The species is believed to be extinct from the southern Transverse and Peninsular ranges, but is still present in Baja California, Mexico.
A number of species prey on California red-legged frogs including raccoons, garter snakes, bass, sunfish, mosquito fish, herons, egrets, cats, foxes, coyotes, and most importantly, the introduced American bullfrog. The most secure aggregations of California red-legged frogs are found in aquatic sites that support substantial riparian and aquatic vegetation for cover and lack exotic predators (e.g., bullfrogs, bass, and sunfish). Bullfrogs are considered one of the main threats to the persistence of this species, and are one reason why California red-legged frogs are found more often in intermittent or seasonal aquatic habitat rather than permanent waters. While California red-legged frogs have been found to co-exist with bullfrogs, the presence of these predators in breeding habitat significantly decreases the survivability of tadpoles, metamorphs, and juveniles, and if allowed to persist, can wipe out an entire population within one breeding pool or stream.
California red-legged frogs are currently threatened by loss of habitat from the growth of cities and suburbs, mining, overgrazing by cattle, invasion of nonnative plants, impoundments, water diversions, degraded water quality, and introduced predators, such as bullfrogs.
The fragmentation of existing habitat and the continued colonization of existing habitat by nonnative species may represent the most significant current threats to California red-legged frogs.
WHAT YOU CAN DO
All endangered and threatened species need your help. Private citizens can play a critical role in protecting our country's wildlife and plants. See What You Can Do to Help Wildlife and Plants (201 KB PDF) for more specific ideas about how to help.
Need more specifics? Download the California Red-Legged Frog scientific species account.