Giraffes at the Safari Park
February 8, 2023

News Release

San Diego Zoo Wildlife Alliance
Public Relations  


Endangered Mouse Raised by San Diego Zoo Wildlife Alliance Certified by GUINNESS WORLD RECORDSTM as Oldest Living Mouse in Human Care  

Title Recognizes a 9-year-old Pacific Pocket Mouse, North America’s Smallest Mouse Species 

SAN DIEGO (Feb. 8, 2023) – San Diego Zoo Wildlife Alliance today received a GUINNESS WORLD RECORDSTM title for Oldest Living Mouse in Human Care recognizing “Pat,” a Pacific pocket mouse fondly named after actor Sir Patrick Stewart. Pat was born July 14, 2013 at the San Diego Zoo Safari Park, in the first year of the organization’s Pacific pocket mouse conservation breeding and reintroduction program. Today, he is 9 years and 209 days old. The GUINNESS WORLD RECORDS title is a win for all the tiny but mighty—and often overlooked—species around the world that play an important role in their ecosystems.  

Team members and local and regional partners were present at a ceremony this morning in which Debra Shier, Ph.D., Brown Endowed Associate Director of Recovery Ecology at San Diego Zoo Wildlife Alliance, who established and continues to oversee the Pacific pocket mouse conservation breeding program, accepted a plaque commemorating Pat’s significant age.  

“This recognition is so special for our team, and is significant for the species,” said Shier. “It’s indicative of the dedication and incredible care we as an organization provide for each species, from the largest to the very smallest. This acknowledgement is also a symbol of appreciation for species that people don’t know much about because they’re not charismatic megafauna, but are just as critical for ecosystem function. These overlooked species can often be found in our own backyards—like the Pacific pocket mouse.” 

The acknowledgement from GUINNESS WORLD RECORDS comes on the heels of a historic Pacific pocket mouse breeding season. In 2022, San Diego Zoo Wildlife Alliance recorded the earliest breeding event and pup birth in the history of the program, and the team helped with producing a record 31 litters, for a total of 117 pups during the spring and summer months. Many of these mice will be reintroduced into native habitats this spring. 

Endemic to coastal scrublands, dunes and riverbanks within about 2 miles of the ocean, the Pacific pocket mouse’s range once stretched from Los Angeles to the Tijuana River Valley. Because of human encroachment and habitat degradation, their numbers dropped sharply after 1932. For 20 years, they were thought to be extinct until a tiny remnant population was rediscovered in 1993 at Orange County’s Dana Point headlands. By then, the species had been reduced to just a few small populations, isolated from one another by long distances and urban barriers. 

Continued declines in Pacific pocket mice populations prompted the establishment of San Diego Zoo Wildlife Alliance’s conservation breeding program in 2012 to help save the species from extinction. San Diego Zoo Wildlife Alliance carries out a breeding program and studies behavior, ecology, genetics, microbiome and physiology to best support genetically diverse, healthy and behaviorally competent mice that are well prepared for reintroduction into native habitats. With the support from Orange County Parks, in 2016, San Diego Zoo Wildlife Alliance, the U.S. Fish and Wildlife Service, and the California Department of Fish and Wildlife began to establish a new population of Pacific pocket mice in Orange County’s Laguna Coast Wilderness Park, and they began to breed without human assistance in 2017.  

Weighing about the same as three pennies, the endangered Pacific pocket mouse is the smallest mouse species in North America. They get their name from pouches in their cheeks used to carry food and nesting materials. Though small, these mice play a crucial role in their ecosystems by dispersing the seeds of native plants and encouraging plant growth through their digging activities.  

In addition to bolstering the species and maintaining high genetic diversity, the breeding program provides the added benefit of increasing the understanding of how to better manage genetic diversity of populations in their native habitats. Because only three small populations of Pacific pocket mice remain, San Diego Zoo Wildlife Alliance’s collaborative efforts to augment population numbers, as well as to study and understand their biology and habitat requirements, are critical in conservation of the species. 


About San Diego Zoo Wildlife Alliance
San Diego Zoo Wildlife Alliance is a nonprofit international conservation leader, committed to inspiring a passion for nature and working toward a world where all life thrives. The Alliance empowers people from around the globe to support their mission to conserve wildlife through innovation and partnerships. San Diego Zoo Wildlife Alliance supports cutting-edge conservation and brings the stories of their work back to the San Diego Zoo and San Diego Zoo Safari Park—giving millions of guests, in person and virtually, the opportunity to experience conservation in action. The work of San Diego Zoo Wildlife Alliance extends from San Diego to eco-regional conservation “hubs” across the globe, where their expertise and assets—including the renowned Wildlife Biodiversity Bank—are able to effectively align with hundreds of regional partners to improve outcomes for wildlife in more coordinated efforts. By leveraging these skills in wildlife care and conservation science, and through collaboration with hundreds of partners, San Diego Zoo Wildlife Alliance has reintroduced more than 44 endangered species to native habitats. Each year, San Diego Zoo Wildlife Alliance’s work reaches over 1 billion people in 150 countries via news media, social media, their websites, educational resources and the San Diego Zoo Wildlife Explorers television programming, which is in children’s hospitals in 13 countries. Success is made possible by the support of members, donors and guests to the San Diego Zoo and San Diego Zoo Safari Park, who are Wildlife Allies committed to ensuring all life thrives.  

All visual assets provided by SDZWA are intended solely for use by journalistic news media agencies only. For commercial usage, please submit a request to SDZWA's Licensing Department.

Link includes:

  • Photos and videos from GUINNESS WORLD RECORDS ceremony on Feb. 8, 2023 
  • Video interview with Debra Shier, Ph.D., Brown Endowed Associate Director of Recovery Ecology, San Diego Zoo Wildlife Alliance 
  • Photos and video of Pat, the 9-year-old Pacific pocket mouse, at the San Diego Zoo Wildlife Alliance conservation breeding center 
  • Video explanation of Pacific pocket mouse conservation efforts narrated by Will Miller, biologist, U.S. Fish and Wildlife Service 
  • Graphics of historic and current range of the Pacific pocket mouse