350 endangered frogs released in California’s San Bernardino mountains

San Diego, California – On Tuesday, a coalition of California institutions celebrated a milestone that’s been decades in the making: more than 350 endangered Mountain Yellow-legged Frogs were released into the wild, marking the first species reintroduction for the Birch Aquarium at Scripps. The release took place in the San Bernardino Mountains at Bluff Lake, a preserve managed by The Wildlands Conservancy.

For the Birch Aquarium team, the moment was both historic and deeply personal. “It was an incredibly exciting and emotional day for our team, as releasing these frogs into the wild marks a historic first for Birch Aquarium,” said Sean Bruce, assistant curator of fishes and invertebrates. “We have been raising these frogs for more than a year, and to finally reach this milestone is truly remarkable.”

Of the frogs released, 220 were raised at the aquarium, while the remainder were raised by the San Diego Zoo Wildlife Alliance and UCLA. Small but striking, the frogs measure between 1.6 and 3.5 inches, with females generally larger than males. Their colors range from olive to brown with dark markings, and their yellow-to-orange hind legs give them their common name. If threatened, they produce a garlic-like odor as a natural defense.

The release was carefully staged. The frogs were transported in coolers up the mountain before being split into two groups. The “hard release” group was placed directly into the lake, while the “soft release” group spent a few days in a monitored man-made habitat where they were fed insects and acclimated before being released into the same lake. Every frog was tagged to aid in long-term monitoring. By varying the release methods, scientists hope to learn which strategy offers the species the best chance at survival and repopulation.

This isn’t the first time conservationists have tried to bring the species back to Bluff Lake. In 2023, more than 70 frogs were released into the same area. According to The Wildlands Conservancy’s conservation director, Tim Krantz, the effort has already made history: “Thanks to these efforts, Mountain Yellow-legged Frogs are hopping around Bluff Lake for the first time since they were last recorded here in 1951.”

The frogs’ return is a fragile but hopeful step. Over the last century, their population has declined by an estimated 90 percent, driven by the introduction of non-native trout, which feed on tadpoles, as well as pesticides, a deadly fungal disease, and habitat degradation linked to cattle ranching.

Conservation groups plan to continue monitoring the newly released frogs several times a year and anticipate releasing more in the future. The long-term goal is to restore the population to the point where the species can eventually be removed from the endangered list.

For now, though, the sight of frogs leaping once again around Bluff Lake—after an absence of more than 70 years—is cause for celebration. It’s proof that careful science, patient collaboration, and sheer determination can help turn the tide for species pushed to the brink.