SF Zoo conservation team releases over 1,000 nearly extinct frogs into natural Yosemite habitat

One of the red-legged frogs prior to its release at Yosemite National Park. One of the red-legged frogs prior to its release at Yosemite National Park. Photo: Courtesy Of The San Francisco Zoo Photo: Courtesy Of The San Francisco Zoo Image 1 of / 63 Caption Close SF Zoo conservation team releases over 1,000 nearly extinct frogs into natural Yosemite habitat 1 / 63 Back to Gallery

The California red-legged frog might be nearly extinct, but two of the unsuspecting amphibians ended up making a difference for their dying species.

On Wednesday, the San Francisco Zoo took to Twitter to announce that, earlier this week, the pair of monumental frogs were the 1,000th – and 1,001st – to be released back into their natural habitat of Yosemite National Park.

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On Monday, we released the 1,000th red-legged frog reared at #SFZoo into @YosemiteNPS! For 3 years, our conservation team has raised the nearly extinct CA red-legged frogs from eggs & tadpoles to reintroduce them to areas from which they disappeared 50 years ago pic.twitter.com/QkG42takMx — San Francisco Zoo (@sfzoo) August 21, 2019

As part of a collaborative effort with the National Park Service, the San Francisco Zoological Society's conservation team spent three years raising the frogs from eggs and tadpoles to fully-grown adults. They disappeared from the area 50 years ago due to the introduction of the non-native bullfrog, considered one of the main threats to the persistence of the species. Habitat loss and disease also contributed to the once-declining population.

"It's fantastic," said Dr. Jason Watters, vice president of wellness and animal behavior at the San Francisco Zoo. "We're very proud to be able to be part of this program that's effectively brought this species back to its true home."

The Yosemite Conservancy, U.S. Fish and Wildlife Service and California Department of Fish and Wildlife also united with the zoo's efforts to support the red-legged frog. The state of California reaffirmed its commitment to protect the species by designating it as the official state amphibian in 2014.

"Without them, we would have a lot to lose," Watters said. "They may seem small, but they're important indicators of ecosystem health and parts of the food web."

Not to mention, they're actually one of the largest frogs native to the western region, with some growing to be over five inches long. They were once a common species, even written about in a short story that brought Mark Twain to fame: "The Celebrated Jumping Frogs of Calaveras County." In the past, over 80,000 were harvested annually for their legs.

But despite the zoo's efforts, some of the frogs didn't make it to the wild. As they were raised, they didn't grow properly or experienced other health-related issues that would prevent them from faring well on their own.

"We want to give the ones we release the best odds – it's already a tough world out there," Watters said.

The zoo houses the rest of the frogs in its "California Conservation Corridor," an exhibit established last July in order to educate patrons about the Bay Area's native species, and how the zoo is attempting restore their local populations. There, the red-legged frogs are lifelong neighbors to mountain yellow-legged frogs, western pond turtles and San Francisco fork-tailed damselflies – one of the rarest damselfly species in the country. Watters said it wasn't until recently that the zoo staff learned how to breed them, and thousands have been released back into their natural homes since.

"We hope to help even more species in the future," Watters said. "It's unfortunate that this sort of work has to be done, but it's promising that we're able to bring these animals out there and they're able to stay."

Amanda Bartlett is an SFGate editorial assistant. Email: amanda.bartlett@sfchronicle.com