9-Year-Old Pocket Mouse Named 'Oldest Living Mouse in Human Care'

The world is a big place for a mouse, especially a tiny mouse that weighs no more than three pennies. For the aptly named Pacific pocket mouse, the smallest mouse species in North America, the world has provided even more challenges than those facing the average mouse.

Endemic to a narrow strip of coastal scrublands, dunes, and riverbanks that once stretched from Los Angeles to the Tijuana River Valley, their numbers started declining sharply in the 1930s, thanks to human encroachment and habitat degradation. In fact, the Pacific pocket mouse was considered extinct for several decades. But in 1994, a small population was rediscovered at Orange County’s Dana Point headlands. It turns out there were a few small populations left, but they were isolated by distance and manmade barriers.

Enter the San Diego Zoo Wildlife Alliance, which launched the Pacific pocket mouse conservation breeding and reintroduction program in 2012 to help save the species from extinction. The first year of the program saw the birth of Pat (named after actor Sir Patrick Stewart), who was born on July 14, 2013.

Now, at 9 years and 209 days old, Guinness World Records has awarded Pat the title of "Oldest Living Mouse in Human Care."

As the San Diego Zoo Wildlife Alliance notes in a press statement announcing the new record, the 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." The Pacific pocket mouse is noteworthy for their dispersing of native plant seeds and abetting plant growth through their digging activities.  

Alliance members and partners attended a ceremony in which Debra Shier, Ph.D., Brown Endowed Associate Director of Recovery Ecology at San Diego Zoo Wildlife Alliance, accepted a plaque for the accomplishment. Shier created and oversees the Pacific pocket mouse conservation breeding program.

“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 acknowledgment 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.” 

As for the Pacific pocket mouse (and its advocates), it's not all just awards and glam. These kids are busy. In 2022, according to the Alliance, the team recorded the earliest breeding event and pup birth in the history of the program, not to mention a record of 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. 

While there is much debate about zoos, the pocket mouse program is a good example of how some zoos have pivoted from entertainment to conservation. In addition to the Alliance's breeding program, the researchers study 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."

Partnering with Orange County Parks, the U.S. Fish and Wildlife Service, and the California Department of Fish and Wildlife, in 2016 the Alliance began to establish a new population of Pacific pocket mice in Orange County’s Laguna Coast Wilderness Park.

As of 2017, the mice have been breeding without human intervention. Not bad for a tiny mouse that was once thought gone forever ... and who can now find its name in the Guinness Book of World Records.