These Rare AF Frogs Raised at SF Zoo Were Just Released Back Into the Wild

The San Francisco Zoo released over 160 endangered Sierra Nevada yell0w-legged frog tadpoles back into the wild, representing a major event in the species’ recovery.

Amphibians are like our ecological canaries in a coal mine. Because of their inherent anatomy — these animals possess semi-permeable epedermises, leaving them susceptible to pollutants — frogs in California have experienced sharp declines in population. One species of frog, the Sierra Nevada yellow-legged frog, has seen a 95% drop in their numbers since 2001; this near extinction-level decrease in their numbers is due to predation from non-native animals, deforestation, and the chytrid fungi — a type of fungus that quite literally immobilizes these frogs and prevent them from properly respiration.


Without human intervention (to, ironically enough, redo and make right by the wrongs we’ve committed against Mother Nature), it’s likely that some species of amphibians would fall off the face of the earth. The currently endangered Sierra Nevada yellow-legged frog is one such example.

Thankfully, the San Francisco Zoo is doing its part to help bolster these frogs in the wild. On Wednesday, June 28th,  166 Sierra Nevada yellow-legged frogs that were reared and raised at the zoo were successfully released into the wild.

Photo: Courtesy of the San Francisco Zoo

According to a press release from the zoo, biologists from the U.S. Forest Service, U.S. Fish and Wildlife Service, and California Department of Fish and Wildlife collected wild Sierra Nevada yellow-legged frog tadpoles that were living in Plumas National Forest back in 2022. Once they were harvested, the tadpoles — which have a survival rate of less than one percent in the wild — were brought to San Francisco Zoo and placed in an amphibian head start program. The zoo’s amphibian stronghold helped read the young, powerless tadpoles into adult frogs in captivity — significantly improving their odds of living out full lives in the wild.

Zoo conservationists also treated half of the frogs with medication treatment for the deadly fungal disease that should help prevent infections. (The remaining frogs were left untreated, so participating biologists can test the effectiveness of such treatments on the frogs’ long-term survival rates.)

“The hope is this treatment will help protect them from the fungus so they can continue to reproduce and repopulate the streams and lakes in this part of the Sierra,” said Jessie Bushell, Director of Conservation at the San Francisco Zoo, adding that the reared tadpoles were reintroduced to the same stream they were collected from.

Photo: Courtesy of the San Francisco Zoo

Per a wildlife biologist at the park, the Plumas National Forest contains several streams that have deep pools, capable of sustaining the frogs through the hot summer months and offering shelter during the winter. Biologists have placed a small identification chip under each frog’s skin, as well as taken a photo of their uniquely identifying chin spot patterns to create a personal profile for each.

With the Endangered Species Act turning 50 years old, the recovery and revitalization of species it protects — such as the Sierra Nevada yellow-legged frog — exists as a shining example of why legislation like this is important to safeguarding flora and fauna.

“This effort is a great example of organizations coming together to help an endangered species recover in the wild. The Endangered Species Act turns 50 years old this year, and the recovery of listed species is dependent on the cooperation of many partners,” said Ian Vogel, senior wildlife biologist at the U.S. Fish and Wildlife Service.

Feature image: Courtesy of SF Zoo

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