L.A. Basin’s Yellow-Legged Frog to Be Protected Under Endangered Species Law

A rare frog that inhabits mountains of the Los Angeles Basin will be declared an endangered species protected by federal law under a proposal announced this week by the U.S. Fish and Wildlife Service.

Abundant before the late 1960s, Southern California’s mountain yellow-legged frog is now in danger of extinction, with probably fewer than 100 adults alive today, according to the federal agency’s proposal.

Only the yellow-legged frogs that live in Southern California are covered by the federal agency’s proposal, which was announced Wednesday. In recent years, small numbers have been found exclusively in the Angeles National Forest, on Mt. San Jacinto, and in a tributary of the Santa Ana River in the San Bernardino Mountains.

“The southern population of mountain yellow-legged frog is declining at an alarming rate,” said Michael J. Spear, manager of the U.S. Fish and Wildlife Service’s California office. “It has disappeared from 99% of its former habitat for reasons that are not fully understood.”

A variety of threats are blamed for the frog’s disappearance, including predation by rainbow trout that have been introduced into streams. Also, intensive recreation, air pollution and other activities that have degraded streams have killed the frogs.

About two inches long, the colorful frog with yellow underlegs lives in snow-fed lakes and streams at moderate to high elevations. They hibernate in winter, and emerge in spring to mate, laying their eggs in shallow, flowing water.

All of the remaining frogs are on U.S. Forest Service land protected from development, but federal wildlife officials said the populations are so isolated that they could easily be wiped out by predators, disease or human activities.

If the wildlife agency finalizes its proposal to add the frog to the endangered species list, activities or projects that threaten its habitat are subject to federal review.

Throughout the world, including much of California, many frog species have been vanishing, and no one knows precisely why. Scientists say their thin skins and dependence on water leave them vulnerable to environmental threats, from ultraviolet light to pesticides.

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Mountain Yellow-Legged Frog

Scientific name: Rana muscosa

Length: 2 to 3 inches

Habitat: Lakes, rivers and streams at moderate to high elevations

Color: Highly variable on top; belly and underlegs vary from lemon to darker yellow

Food: Beetles, flies, ants, bees and wasps

Predators: Trout, coyotes, birds, garter snakes

Range: Fewer than 100 frogs are estimated to survive in Southern California in the San Gabriel and San Bernardino mountains.