����������

American pika (Ochotona princeps). (Credit: Steve Torbit/USFWS)

A new study led by the ���������� Boulder carries a warning for one of the Rocky Mountains’ most iconic animals—the American pika (Ochotona princeps), a small and fuzzy creature that often greets hikers in Colorado with loud squeaks.

The study draws on long-running surveys of pikas living in a single habitat about 10 miles south of Rocky Mountain National Park in Colorado.

The researchers discovered that the “recruitment “of juveniles to this site seems to have plummeted since the 1980s. In other words, these populations are becoming dominated by older adults, with fewer juvenile pikas being born, or migrating in, to take their place.

The group in the journal “Arctic, Antarctic, and Alpine Research.”

An American pika in Yellowstone National Park. (Credit: Adobe Stock)

Chris Ray makes notes during a survey of pikas in Colorado's Indian Peaks Wilderness. (Credit: Gabe Allen/INSTAAR)

Graduate student Rachel Mae Billings releases a pika after collecting data in Colorado's Indian Peaks Wilderness. (Credit: Gabe Allen/INSTAAR)

“It’s a fun encounter when you’re hiking on a trail in the Rockies and a pika yells at you,” said Chris Ray, lead author of the study and a research associate at the Institute of Arctic and Alpine Research (INSTAAR) at ���������� Boulder. “If you don’t have that anymore, your experience in the wild is degraded.”

She added that scientists have long predicted that climate change might threaten pikas in the American West.

One 2015 study entirely from Rocky Mountain National Park by the end of the century.

Ray and her colleagues can’t yet pinpoint the reason pika recruitment may be declining at this one site. But summers have been growing warmer at sites in the Rocky Mountains—a concerning bellwether for ecosystems that humans depend on.

“The habitats where pikas live are our water tower,” Ray said. “The permafrost, or seasonal ice, that’s underground here melts later in the summer and helps replenish our water supplies at a time when reservoirs are draining.”

Rock piles

The research takes a close look at the site north of Nederland, Colorado.

Niwot Ridge is home to sweeping tundra meadows and steep hillsides dotted with boulders. It’s also home to pikas. These animals have round ears and are about the size of rats, although they’re more closely related to rabbits and hares.

From 1981 to 1990, Charles Southwick, a former professor at ���������� Boulder, set out to follow the pika populations at Niwot Ridge. His team trapped and tagged pikas, which tend to stick close to taluses, or piles of rocks.

Ray has studied these animals in the American West, from Montana south to Colorado, for more than 35 years.

At Niwot Ridge, she took up Southwick’s mantle by using similar methods to survey pikas at this location in 2004 and from 2008 to 2020. The team takes rigorous precautions to ensure the health and safety of the animals.

“Pikas are useful as a study system because they're so visible and conspicuous, and they’re one way to get a handle on what changes are happening in alpine ecosystems,” Ray said.

In the current study, she and Jasmine Vidrio, a former undergraduate at ���������� Boulder, compared their findings to what Southwick saw decades earlier.

The results were disturbing.

Quiet hillsides

Based on the researchers' calculations, the proportion of pikas they trapped that were juveniles fell by roughly 50% from the 1980s to today—suggesting that younger pikas could be growing rarer on Niwot Ridge.

Ray explained that pikas may be especially vulnerable to climate change, in large part because they can only survive in a narrow range of temperatures.

“Pikas don’t pant like a dog. They don’t sweat,” she said. “The only way they can release their metabolic heat is to get into a nice, cool space and just let it dissipate.”

The researchers can’t conclusively link the possible decline of pikas on Niwot Ridge to warming temperatures. They also aren’t sure how widespread this trend is in the West.

But Ray noted that her results support previous predictions that juvenile pikas may have trouble migrating through the Rockies as temperatures continue to warm. To cross from one mountain habitat to another, pikas first have to climb down in elevation, facing hot conditions in the process.

She recalls one pika she encountered at the start of her career in the 1990s. She nicknamed the male Mr. Mustard because he had yellow tags on his ears.

“He was an adult when I trapped him, and he lived for nine more years,” Ray said. “I don’t see that anymore, so I do think things are changing.”