Hundreds of Threatened Frogs Released in Santa Monica Mountains

California red-legged frog | Photo: Charles Peterson/Flickr/Creative Commons License

The Santa Monica Mountains are once again home to California's official state amphibian. After a release of ready and willing tadpoles earlier this week, the mountain range that separates the Los Angeles Basin from the San Fernando Valley has a population of the California red-legged frog for the first time in about 40 years.

The tadpoles were released from protective mesh cages into two unidentified streams in the Santa Monicas, according to wildlife biologists. The cages were placed in the streams in March, along with red-legged frog egg masses biologists collected from an isolated population in the Simi Hills. (We'd written about the Simi Hills frogs a few months earlier.)

The 850 tadpoles now plying those mountain streams make up the first-ever effort to expand the range of the federally Threatened species in Southern California.

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"California red-legged frogs haven't been seen in the Santa Monica Mountains since the early 1970s," said National Park Service wildlife ecologist Katy Delaney, who spearheaded the effort to reintroduce the frog to the Santa Monicas. "Hopefully these tadpoles can help reverse the population decline of native frog species locally and across the state."

Other agencies working with the National Park Service to reintroduce red-legged frogs to the Santa Monicas are the California State Parks, the Mountains Recreation and Conservation Authority, the Mountains Restoration Trust, the Santa Monica Bay Restoration Commission, the U.S. Fish and Wildlife Service and U.S. Geological Survey's Western Ecological Research Center.

The California red-legged frog, Rana draytonii, was once one of the most common frogs throughout its range. The frog thrived in coastal wetlands south of Mendocino through Baja, as well as watercourses in the Sierra Nevada and the mountains that surround the Sacramento Valley.

But a century and a half of harvesting for food, destruction of native stream habitat, and introduction of exotic predators and competitors have done serious damage to red-legged frog numbers. Listed as Threatened under the U.S. Endangered Species Act in 1996, the frog has suffered especially serious declines in the Sierra Nevada and in Southern California.

Katy Delaney holds one of the tadpoles | Photo: National Park Service

When the survivors among the 850 tadpoles released this week metamorphose into adult frogs and grow to maturity, they'll reach lengths of up to five inches. The frogs tend to prefer pond habitat when it's available, though they can be found in streams, moist vegetated spots far from open water, or even sealed into the dried out mud of seasonally dry pools.

The new Santa Monica Mountains population of Rana draytonii still has an uphill battle: frogs are especially susceptible to environmental contaminants such as pesticides due to their highly absorbent skin. Loss of habitat due to climate change and increasing drought are also looming threats. Still, we'll take out good news wherever we can find it.

About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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