News Release

For the First Time, Threatened California Red-Legged Frogs Are Independently Breeding at Two Reintroduction Sites

A California red-legged frog found in the spring of 2021 by biologists in the Santa Monica Mountains.

National Park Service

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News Release Date: June 29, 2021

Contact: Ana Beatriz Cholo, 805-750-9356 (cell); 805-370-2385 (office)

THOUSAND OAKS, Calif. – National Park Service biologists have discovered California red-legged frogs (Rana draytonii), a threatened species, independently breeding at two sites that were severely impacted by the Woolsey Fire. These sites have not had wild breeding for perhaps as long as half a century. Click here for photos.

During recent stream surveys, researchers spotted three egg masses at one site in Los Angeles County. At a different Ventura County site, biologists found one female and one male frog and then, a week later, voila - a single egg mass. This was proof that the frogs were successfully breeding on their own. All egg masses have since successfully hatched.

"It was a welcome surprise," said Katy Delaney, an ecologist at Santa Monica Mountains National Recreation Area who has been leading the project for the last decade.

In 2014, NPS biologists set up two stream sites to reintroduce the species back into the Santa Monica Mountains. Two years later, egg masses were reintroduced into two additional stream sites. These are the two sites that are currently experiencing new activity.

A population discovered in the nearby Simi Hills has been used to replenish these four locations in the mountains. Translocated eggs were reared into tadpoles and released in the four streams. The idea was that translocated individuals would eventually mature, mate, and reproduce on their own. 

The project was humming along before the Woolsey Fire in November 2018. Frogs were surviving in each of the four streams - from tadpoles to grown adults. The grown adults in the first two reintroduction sties had already begun breeding independently. For the two newer sites, it was still a bit too early for reproduction. 

The wildfire was closely followed by catastrophic mudslides that wiped out much of the frog's habitat. The frogs require deep breeding pools of year-round water and foliage, which is not easy to find in the arid Santa Monica Mountains. Many streams were filled in with silt, mud, and debris. 

Because frogs are picky about where they breed, Delaney had doubts about their future, and thus, the future of her project. 

She wondered if this might be the end for these newly reestablished populations of nocturnal amphibians. However, she is pleased that the frogs proved more resilient than she initially thought.

"Here we are two years later, and the streams have recovered enough to create pools that the frogs must have liked," Delaney said. 

The exception is one of the reintroduction sites that was introduced in 2014. The habitat is in poor shape, and very low numbers of frogs have been surveyed, according to the researchers. Frogs were breeding there prior to the Woolsey Fire, but they have not since.

Regardless, biologists see this latest development as a positive milestone for the project because now every reintroduction site has had successful wild breeding. 

“This is one more step towards our goal of self-sustaining populations of these frogs in our region,” said Delaney.
 
Biologists are doing regular surveys for tadpoles. Later this summer, they will be on the lookout for froglets. 

The last known record of California red-legged frogs in the Santa Monica Mountains was in the 1970s. As a result, they are listed as federally threatened under the Endangered Species Act and are a state Species of Special Concern. 

Partners in the reintroduction project are California State Parks, the Mountains Recreation and Conservation Authority, the Santa Barbara Zoo, the Santa Monica Bay Restoration Commission, the Santa Monica Mountains Conservancy, California State Coastal Conservancy, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey (USGS).

Santa Monica Mountains National Recreation Area (SMMNRA) is the largest urban national park in the country, encompassing more than 150,000 acres of mountains and coastline in Ventura and Los Angeles counties. A unit of the National Park Service, it comprises a seamless network of local, state, and federal parks interwoven with private lands and communities. As one of only five Mediterranean ecosystems in the world, SMMNRA preserves the rich biological diversity of more than 450 animal species and 26 distinct plant communities. For more information, visit nps.gov/samo.

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Last updated: June 29, 2021

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