California: rare frogs released into the mountains


More than two years after being released from California’s San Gabriel Mountains by the Bobcat Fire, endangered yellow-legged mountain frogs have been released back into their native habitat.

The Aquarium of the Pacific acquired a total of 275 yellow-legged tadpoles last July, according to Erin Lundy, who helps care for the aquarium’s frogs.

The aquarium received two cohorts of tadpoles: one and a half cohorts of tadpoles bred at the Los Angeles Zoo and rescued in a wildfire that destroyed their natural habitat.

“Over the last year, we’ve been slowly and steadily growing into frogs,” Lundy told CNN. The species can take four to five years to mature from tadpole birth to the adult frog stage, Lundy added. But they wanted to wait for the tadpoles to mature before releasing them; adults are “tougher” than tadpoles, he said.

On Sept. 15, a group of 188 fully grown frogs were released back into the San Gabriel Mountains, according to Lundy. Half were from the rescued cohort and half were from the captive-bred cohort. The release is especially exciting given how endangered the frogs are: fewer than 200 adults remain in the wild.

“Being able to release over 180 frogs was very meaningful to us,” Lundy said.

Amphibians like frogs play a key role in the ecosystem, according to Lundy. “When you remove amphibians from a habitat, you’re really losing all those parts of that interconnected food web, and that can be quite detrimental to the functioning of the ecosystem,” he explained.

Mountain yellow-legged frogs prey on insects, including beetles, ants, and flies. And they have a unique survival tactic: They can emit a strong garlic-like odor as a defense mechanism when they feel threatened, Lundy said.

The species used to be quite populous in the US, Lundy said. But when humans introduced invasive predators like trout, which feed on tadpoles, their numbers plummeted.

“Mountain yellow-legged frogs didn’t have too many natural predators, which is why they were so crowded and why they could take so long to breed,” he continued. “And they lived at very high altitudes, and streams and waterways that usually didn’t have fish in them.”

But the introduction of fish species for recreational fishing “decreased their population greatly, in addition to infectious diseases and other things that have been introduced to these animals over time.”