Alpine Chipmunks’ Habitat and Gene Pool are Shrinking

One of the few mammals unique to California is also one of the most threatened by climate change.

The alpine chipmunk only lives in California, and its habitat is shrinking.

The alpine chipmunk, found in Yosemite’s high country, has moved upslope as temperatures have warmed over the last century.

Now a new study out yesterday from the journal Nature Climate Change shows a warming climate may also be affecting the species’ genetic diversity. Listen to my radio story about the study on today’s California Report.

The alpine chipmunk is one of the smallest chipmunks in California. It’s also got a uniquely striped face. It’s hard to see these chipmunks in the wild unless you strap on a backpack and climb some 10,000 feet high in the Sierra.

That’s what study author Emily Rubidge did as a PhD student at UC Berkeley’s Museum of Vertebrate Geology. She’s part of a team that’s been ambitiously updating Joseph Grinnell’s historic survey of Yosemite’s wildlife from the early 1900s.

The team first found that the alpine chipmunk had pushed its habitat some 1600 feet higher into the Sierra over the last century, a period when average temperatures in the park increased by about 5.4 degrees Fahrenheit. Back in the early 1900s, Grinnell and his colleagues sighted alpine chipmunks at elevations of 7,800 feet. More recently, researchers couldn’t find the species any lower than 9,600 feet.

Rubridge also compared DNA of century-old dried specimens and skeletons Grinnell collected for the Museum of Vertebrate Zoology to samples she took from the ears, toes and tails, of alpine chipmunks today.

She found that the chipmunks living at higher elevations showed a startling decline in the species’ genetic diversity compared to samples from the early 20th century.

“This new work shows that, particularly for mountain species like the alpine chipmunk, such shifts can result in increasingly fragmented and genetically impoverished populations,” said Rubidge. “Under continued warming, the alpine chipmunk could be on the trajectory toward becoming threatened or even extinct.”

A more limited gene pool means the chipmunks could face problems caused by inbreeding or disease. And could also be less likely to adapt to changing environments.

This study is one of the first to show actual impacts on genetic diversity because of warming temperatures, evidence that climate change could already be altering life for mammals unique to California.