Conservation Genetics of the Pacific Pocket Mouse

The diminutive Pacific pocket mouse, once thought to be extinct, then found to survive on Orange County’s Dana Point headlands, is another species that the San Diego Zoo Institute for Conservation Research is working to bring back from the brink of extinction.

Additional populations of Pacific pocket mice have been discovered at South San Mateo and at Camp Pendleton, so that these three locations provide the remaining strongholds of the tiny mice whose life cycle is aligned with the availability of small seeds from grasses that they store in underground caches.

In collaboration with the U.S. Fish and Wildlife Service, samples collected for genetic analysis as part of trap-and-release census studies at the three sites, are providing valuable information that is being utilized for structuring the recovery efforts for this highly endangered species.

From the more than seventy individuals sampled in the three populations, DNA profiles have been obtained that attest to the genetic isolation of these populations. Even fifty years ago, additional populations with habitat connections between them may have existed that facilitated the dispersal of young or the migration of males.

Today, various roads, multi-lane interstate freeways, numerous residential and commercial buildings, and general loss of habitat make such movements impossible. The entire gene pool of the species is now distributed among populations in the three remaining locations where Pacific pocket mice survive. Each one of these populations is important for the survival of the species, and recovery efforts are focused on establishing additional populations.

Genetic studies that revealed the genetic distinctiveness of the remaining populations strongly support the need to establish additional populations that mimic historic patterns of gene flow among populations that contributed to their survival. The boom and bust of annual cycles in rainfall and seed abundance make the Pacific pocket mouse vulnerable to population crashes.

The maintenance of habitat suitable for connecting isolated population fragments, establishment of new populations, and carefully managed translocations offers hope for the future of these amazing little mice.