Return of the Southern Mountain Yellow-Legged Frog at Bluff Lake

Mountain Yellow-Legged Frog at Bluff Lake / photo by Elba Mora

Bluff Lake Reserve is once again home to the Southern Mountain Yellow-legged Frog — a species that had been missing from this habitat for more than 70 years. The first release took place in summer 2023, and this August, the largest release yet brought 361 more frogs to the lake.

Once common in Southern California’s mountain streams, these small, moss-colored frogs have nearly disappeared from the region due to habitat loss, invasive predators, pesticides, and disease. In the San Bernardino Mountains, their population fell to fewer than 20 individuals in one creek. In 2011, the last frogs were collected and raised in captivity by the San Diego Zoo Wildlife Alliance and partners — the only way to keep them from vanishing entirely.

“To see these frogs return to Bluff Lake is to see a missing piece of the ecosystem put back in place,” says Tim Krantz, The Wildlands Conservancy’s Conservation Director. “It’s a crucial step toward restoring biodiversity in the San Bernardino Mountains.”

In 2023, half the frogs released spent a week in protective enclosures to adjust, while the rest swam free immediately. In August 2025, a solar-powered biomonitoring array was installed at the lake, and the second release of 361 frogs marked the largest yellow-legged frog release ever at Bluff Lake. Biologists can now track individual frogs and monitor how they adapt to their habitat.

The frogs’ return is part of a larger rewilding effort to restore missing species and strengthen whole ecosystems. Healthy frog populations benefit birds, fish, and aquatic plants, and their presence signals a balanced, functioning habitat. Around the same time as the first frog release in 2023, biologists also reintroduced the critically endangered unarmored threespine stickleback. Since then, the fish have established successfully at Bluff Lake, with breeding populations now contributing to the lake’s ecological recovery.

Together, these initiatives show how careful, coordinated conservation can restore balance and vitality to Bluff Lake. By reintroducing species once thought lost and working alongside our dedicated partners, we are strengthening biodiversity and creating a healthier, more resilient ecosystem.

Mountain Yellow-legged Frog release day at Bluff Lake / photo by Elba Mora

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