An endangered mouse may need a helping hand to adapt to climate change

A tiny mouse on the brink of extinction in coastal California may be able to adapt to a hotter world — though it might need a little help. 

Genetic analyses of critically endangered Pacific pocket mice suggest the species has the genetic diversity to adapt to a changing climate, researchers report April 17 in Science Advances. But urbanization has isolated the remaining animals, and conservation efforts may be necessary to help spread genes linked to acclimation. 

The range of the Pacific pocket mouse (Perognathus longimembris pacificus) once spanned the southern California coast from Los Angeles to Mexico. The critter went undetected for more than two decades but was rediscovered in the early 1990s, gaining protection under the U.S. Endangered Species Act. Now, just three small groups south of Los Angeles remain. 

Endangered species can struggle to adapt to environmental changes, in part because inbreeding can strip away the genetic diversity needed for a species to evolve. The three wild Pacific pocket mouse populations have shrunken due to habitat loss, says Erik Funk, a conservation geneticist with the San Diego Zoo Wildlife Alliance. In 2012, researchers launched a conservation program at the zoo that breeds individuals across the three groups and releases offspring into the Laguna Coast Wilderness Park in Laguna Beach, Calif. 

To uncover how resilient wild and reintroduced Pacific pocket mice might be to climate change, Funk and colleagues analyzed genetic blueprints from mice collected over nearly a century. While modern mice are more inbred, 14 genes that could help the species adapt to climate change retain some diversity. Some genes are related to heart function, which could help animals cool down. 

Whether the three wild groups could individually adapt to a warmer world is unclear, but genetic analyses showed that the released animals with mixed genes may already be adjusting to the wilderness park’s climate. “The real benefit for this released population is that they’re all mixed together,” Funk says. “In the wild populations, there’s some variation that exists in one population, some variation that exists in another. The biggest benefits, we think, come when we can combine all this diversity together.” 

It’s unclear how many Pacific pocket mice are left. Disasters such as flooding or severe drought can further push vulnerable species toward extinction. And as more animals perish, the remaining genetic diversity declines. “Once that’s lost,” Funk says, “it can’t be brought back.”