One of North America’s tiniest and most endangered mammals just got a big reason to celebrate. The San Diego Zoo Wildlife Alliance has established a third reintroduced population of Pacific pocket mice, this time at North San Mateo on Marine Corps Base Camp Pendleton — marking 20 years of a conservation program that has already released more than 500 of these thumb-sized rodents back into the wild.
The Pacific pocket mouse weighs about as much as three pennies, yet its impact is enormous. These little diggers are ecosystem engineers: their burrows improve soil hydrology and nutrient cycling, and they provide shelter for other species across Southern California’s coastal ecosystems. Once thought extinct, the species was rediscovered in 1993 and remains one of the continent’s most endangered mammals, with only three original wild populations left.
The recovery is a team effort. The Alliance works alongside the U.S. Fish and Wildlife Service, the California Department of Fish and Wildlife, the U.S. Geological Survey, and Marine Corps Base Camp Pendleton. The first reintroduced population took root in Laguna Coast Wilderness Park in 2016, followed by a second at Camp Pendleton in 2024 — and now a third is settling into its new home.
“Establishing this new population at Camp Pendleton is an exciting step toward the species’ recovery,” said Debra Shier, the Alliance’s Brown Endowed associate director of recovery ecology.
Good news for a species that fits in the palm of your hand — and for everyone who believes small things can change the world.
Photo: San Diego Zoo Wildlife Alliance
