CALIFORNIA RED-LEGGED FROG
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Description:
The abdomen and hind legs of adults are red; the backs are characterized
by small black flecks and larger irregular dark blotches with
indistinct outlines on a brown, gray, olive, or reddish background
color. Dorsal spots usually have light centers. Skin folds across the
back are common. In their tadpole stage, the frogs are dark brown and
yellow with darker spots.
Size: At up to 5 inches long, the California
red-legged frog is one of the West's largest native frogs. Females grow
larger than males. The larvae range from .6 to 3.1 inches.
Habitat: Adult frogs require dense, shrubby or
emergent riparian vegetation closely associated with deep still- or
slow-moving waters. During winter, well-vegetated areas along these
river corridors are needed for shelter.
Range: Remaining populations of the red-legged frog
are found mostly in three California counties: Monterey, Santa Barbara,
and San Luis Obispo. The frog's historical range extended from the
vicinity of Point Reyes National Seashore, Marin County, California,
coastally, and from the vicinity of Redding, Shasta County, California,
inland south to northwestern Baja California, Mexico.
Life Cycle: Eggs are laid, which hatch in 6 to 14
days. Larvae (tadpoles) undergo metamorphosis in 3.5 to 7 months. Sexual
maturity is attained at around 3 to 4 years of age. California
red-legged frogs may live 8 to 10 years.
Food Source: The diet of California red-legged frogs
is extremely variable. Invertebrates, small tree frogs and mammals are
eaten by adults, while larvae are thought to feed on algae.
Population: In the past, over 80,000 red-legged
frogs were harvested annually for their legs. Currently, while exact
numbers are unknown, only three localities are known to support
substantial (over 350) populations of adult frogs.
Voice: California red-legged frogs have paired vocal
sacks, and usually call into the air.
Behavior: In general, adult frogs are quite wary.
Highly nocturnal, they come under attack from wading birds. Adult frogs
seem to use vibrations transmitted along the vegetation on which they
are sitting to detect the approach of certain other predators, such as
raccoons. They also sometimes fall prey to San Francisco garter snakes
and two-striped garter snakes, with which they share certain habitat.
During periods of flooding, California red-legged frogs have been
observed concealed in small pockets or mammal burrows along river banks,
stabilized by shrubby riparian growth.
Reproduction: California red-legged frogs breed
early in the year, from late November to late April. Males appear at
breeding sites typically 2-4 weeks ahead of females, and call in small
mobile groups of between 3 and 7 to attract females. Egg masses
containing between 2,000 and 5,000 small (.1 inches in diameter), dark,
reddish-brown eggs are attached to vegetation in or near the water, such
as bulrushes or cattails.
Survival Threats: Bullfrogs, introduced to supply
frog legs for restaurants in the face of declining numbers of the
California red-legged frog, eat their eggs, and replace them in their
habitat. Clearing of creek-bed vegetation and the creation of concrete
banks threatens the frog's breeding habitats, as well as other forms of
water-diversion associated with development.
Legal Protection: Endangered Species Act; Species of
special concern in the state of California.
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