SANTA CRUZ >> The American pika, a rabbit-like fur ball that lives in the rocky slopes of mountains in the American West, is disappearing in California.

A recent study finds that rising temperatures appear to be driving some pika populations extinct in low elevation sites in the Sierra Nevada.

Using historical data, researchers found that pikas are no longer found in 15 percent of their California range, places that are on average 2.2 degrees warmer than sites where they remain. They predict that by 2070, pikas will have disappeared from nearly 40 to 90 percent of those sites, depending on how much summer temperatures actually rise.

“It’s troubling,” said lead author Joseph Stewart, a graduate student at UC Santa Cruz. “This sort of points the finger at climate change.”

The study was published in the Journal of Biogeography.

With thick fur — even inside their ears and on the bottoms of their feet — ­­pikas are adapted to the cold temperatures in high-elevation boulder fields and alpine meadows. They don’t hibernate and need to maintain a high body temperature to survive the winter, which they prepare for by spending the summer harvesting grasses.

“Hikers often see them hopping across the rocks and carrying little bouquets of wildflowers in their mouth,” Stewart said. “A lot of the locations that hikers go to, the lower elevations for pikas, that’s where we’re losing them.”

Hotter summer temperatures force pikas underground to hide from the heat, giving them less time to forage. Spending as few as six hours in weather as low as 78 degrees can be fatal. Rising temperatures also threaten the tiny animal by altering the types of plants in the already shrinking alpine meadows and melting snowpacks, which insulate their burrows.

Three pika communities near Crater Lake in Oregon have vanished in recent decades, according to the National Park Service.

“Pikas have become a poster child for climate change’s impacts,” said Stewart.

Trapped on isolated slopes, the sensitive tiny critter can’t adapt and migrate like other animals.

“A bird just has to pick up and fly,” Stewart said. “If a pika wants to get from one mountain peak that isn’t cold enough to another one that is colder, oftentimes it’s going to have to go down into hotter, lower-elevation areas. The problem is their habitat doesn’t go high enough in California.”

The California Fish and Game Commission and U.S. Fish and Wildlife Service denied petitions to list pikas under the state and federal endangered species acts, ruling that the pika’s peril a distant threat.

“This study shows that the pikas are disappearing now because it’s getting too hot,” said Shaye Wolfe, climate science director for the Center of Biological Diversity. “There’s been a decade’s worth of study saying that pikas are seriously threatened by global warming.”

On the Net: To view the study, visit The Journal of Biogeography.