"If you were a miner in California during the Gold Rush, you might have dined on a California red-legged frog.

The largest native frog in the western United States, this Golden State denizen used to be found as far inland as the Sierra Nevada mountains and south, into Baja California. But overharvesting, predation by invasive bullfrogs and habitat loss took their toll on the frogs: Today, they're listed as threatened under the Endangered Species Act.

Over the past five years, a team of conservationists carefully translocated a population of these red-legged frogs, moving them from northwestern Mexico to two sites in California. Once they got there, though, they were stuck with another problem: how to monitor that population's growth."

Nathan Rott, Hannah Chinn, Regina G. Barber, and Rebecca Ramirez report for NPR July 18, 2025. [2]