USGS ARMI-led conservation program reaches milestone with release of 600 endangered frogs into San Gabriel Mountains

LOS ANGELES, CA – In a remarkable step forward for amphibian conservation, over 600 endangered southern mountain yellow-legged frogs were released into their native habitat in the San Gabriel Mountains earlier this month. The coordinated release — involving 450 tadpoles and 193 subadult frogs — is part of the long-running Southern Mountain Yellow-Legged Frog Recovery Program, led by the U.S. Geological Survey’s Amphibian Research and Monitoring Initiative (ARMI) in partnership with the Los Angeles Zoo, Aquarium of the Pacific, and other agencies.

This program, established in 2006, is one of the most significant amphibian recovery efforts in the country, and the USGS ARMI has played a central role from the outset. As the lead scientific agency, ARMI provides research, monitoring, and strategic oversight for the entire conservation initiative, using decades of expertise in amphibian population science to guide partner efforts and evaluate long-term success.

The recent July 2025 release, carried out at a remote, undisclosed location to protect the animals and their fragile environment, represents a continuation of nearly two decades of strategic reintroductions. Most of the released frogs were bred at the Los Angeles Zoo in a highly controlled, bio-secure facility built specifically for the species. With support from the USGS and partners, the zoo has produced over 6,000 frogs since 2007, all released under carefully monitored conditions to reestablish wild populations.

The species, Rana muscosa, has experienced dramatic population declines in recent decades due to disease, habitat loss, non-native predators, drought, and environmental degradation. Once abundant throughout Southern California’s mountain ranges, these frogs are now classified as Endangered by the IUCN.

Recognizing the urgency of the situation, USGS launched the ARMI initiative in the early 2000s to respond to amphibian declines nationally. The Southern Mountain Yellow-Legged Frog Recovery Program remains a flagship example of ARMI's mission in action. Through intensive monitoring, habitat modeling, and close coordination with state and federal agencies, ARMI ensures that each step in the recovery process — from breeding to release to long-term population tracking — is rooted in scientific evidence.

For more info on the release, please visit the L.A. Zoo's news story: https://lazoo.org/2025/07/l-a-zoo-releases-450-zoo-bred-endangered-frog-tadpoles-into-san-gabriel-mountains/.