Milestone marks 20 years of conservation efforts to recover one of North America’s most endangered mammals

SAN DIEGO, Oct. 6, 2026 /PRNewswire/ — San Diego Zoo Wildlife Alliance has helped establish a third reintroduced population of endangered Pacific pocket mice at North San Mateo, a training area within Marine Corps Base Camp Pendleton.

The milestone comes as San Diego Zoo Wildlife Alliance celebrates 20 years of conservation efforts to recover Pacific pocket mice in Southern California. Since launching its Pacific Pocket Mouse Conservation Program in 2006, San Diego Zoo Wildlife Alliance has released more than 500 Pacific pocket mice into new and existing populations throughout the species’ native range.

“Establishing this new population of Pacific pocket mice at Camp Pendleton is an exciting step toward the species’ recovery,” said Debra Shier, Ph.D., Brown Endowed Associate Director of Recovery Ecology at San Diego Zoo Wildlife Alliance. “Pacific pocket mice are ecosystem engineers, and their impact goes far beyond their small size. By digging their burrows, they help improve soil hydrology and nutrient cycling, while their burrows provide shelter for other species. Establishing another population helps bring these important ecological functions back to the coastal ecosystems where Pacific pocket mice naturally occur.”

The Pacific pocket mouse is the smallest and one of the most endangered mammals in North America, measuring about the size of a human thumb and weighing approximately as much as three pennies. Once thought to be extinct, the species was rediscovered in 1993 when a small remnant population was found in Orange County. Following its rediscovery and emergency listing under the federal Endangered Species Act, conservationists began working to prevent the Pacific pocket mouse from disappearing again. Today, only three original populations persist in the wild, and the species remains an important part of Southern California’s coastal ecosystems.

In 2006, San Diego Zoo Wildlife Alliance launched its Pacific Pocket Mouse Conservation Program to help recover the species throughout Southern California. Since then, the program has advanced scientific understanding of Pacific pocket mice and developed conservation strategies to protect existing populations, restore habitat, and establish new ones. In 2012, the program added a conservation breeding effort to produce genetically diverse and behaviorally competent mice for release into their native habitat.

The first reintroduced population was established in Laguna Coast Wilderness Park in Orange County in 2016. A second was established at Marine Corps Base Camp Pendleton in 2024. The new population at North San Mateo represents the third reintroduced population established through the collaborative conservation program.

The effort is part of a collaborative partnership between San Diego Zoo Wildlife Alliance, the U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, U.S. Geological Survey, and Marine Corps Base Camp Pendleton. Together, the organizations have worked to protect and grow Pacific pocket mouse populations, restore and manage habitat, and develop the scientific knowledge needed to support the species’ recovery.

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• Photos and b-roll of the Pacific pocket mouse reintroduction

About San Diego Zoo Wildlife Alliance

San Diego Zoo Wildlife Alliance, a nonprofit conservation leader, inspires passion for nature and collaboration for a healthier world. The Alliance supports innovative conservation science through global partnerships and groundbreaking efforts at the world-famous San Diego Zoo and San Diego Zoo Safari Park, both leading zoological institutions and accredited botanical gardens. Through wildlife care expertise, cutting-edge science and continued collaboration, more than 44 endangered species have been reintroduced to native habitats. The Alliance reaches over 1 billion people annually through its two conservation parks and media channels in 170 countries, including San Diego Zoo Wildlife Explorers television, available in children’s hospitals across 14 countries. Wildlife Allies—members, donors and guests—make success possible. 

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SOURCE San Diego Zoo Wildlife Alliance