Young pikas are quietly vanishing in the Rocky Mountains

Pikas greet a lot of Colorado hikers before they ever see the animals themselves. Their sharp squeaks echo out from the rocks, giving these tiny mountain mammals a big presence in the high country.

But now, the familiar call of the pika is growing quieter at a well-studied site in the Rockies. A long-running survey on one Colorado mountainside shows that fewer young animals are joining the population.

The work suggests that the community of pikas there is shifting toward older adults, with fewer juveniles stepping in to replace them.

The lifestyle of a pika

The American pika (Ochotona princeps) is a small and fuzzy animal with round ears, about the size of your fist. It is more closely related to rabbits and hares than to rodents.

In Colorado and across many western mountains, pikas live among broken rock piles near the tops of peaks, greeting visitors with loud squeaks.

Pikas cut and stash plants in little hay piles to get through long winters. They also feed predators such as weasels and birds of prey.

Because they are easy to see and to hear, changes in pika numbers quickly catch human attention.

Decades on a mountain ridge

The new study was led by Chris Ray, a research associate at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado Boulder, and colleagues.

The work focuses on a habitat about 10 miles south of Rocky Mountain National Park, at the Niwot Ridge Long Term Ecological Research site north of Nederland, Colorado.

Niwot Ridge holds wide tundra meadows and steep hillsides covered in boulders, and it has been watched closely by scientists for decades.

From 1981 to 1990, CU Boulder Professor Charles Southwick and his team trapped and tagged pikas that stayed close to taluses, or piles of rocks.

Ray has studied pikas in the American West from Montana south to Colorado for more than 35 years. At Niwot Ridge she returned to Southwick’s site using similar methods in 2004 and again from 2008 to 2020, with rigorous precautions to protect the animals.

Working with former CU Boulder undergraduate Jasmine Vidrio, Ray compared the new surveys with the older records.

“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.

Fewer young pikas on the rocks

That long record let the team spot a worrying pattern. The researchers discovered that the “recruitment “of juveniles to this site seems to have plummeted since the 1980s.

In plain terms, the community is now dominated by older adults, with fewer young pikas being born there or moving in from elsewhere.

Based on the team’s calculations, the proportion of pikas the team trapped that were juveniles fell by roughly 50% from the 1980s to today.

The researchers cannot yet pinpoint the reason for this change at Niwot Ridge, and they do not know how common this pattern is across the West. They also cannot conclusively link the local drop in juvenile pikas to temperature alone.

Pikas have a narrow comfort zone

Even so, the species has been on scientists’ radar for years. Ray noted that researchers have long predicted that climate change might threaten pikas in the American West.

One 2016 study predicted that pikas could disappear entirely from Rocky Mountain National Park by the end of the century. Summers have also been growing warmer at alpine sites in the Rockies, a concerning bellwether for ecosystems that people rely on.

Part of the problem is biology. “Pikas don’t pant like a dog. They don’t sweat. The only way they can release their metabolic heat is to get into a nice, cool space and just let it dissipate,” noted Ray.

Warmer days leave them with less safe time to forage on the surface. Earlier work suggested that young pikas may struggle to move between mountain habitats as temperatures rise, because they must first travel downslope through hotter conditions.

“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.”

Changes in pika populations can therefore hint at deeper shifts in snow, ice, and water in high basins.

Signs of a changing alpine system

The pika is not just an interesting data point. It is also part of the experience of being in the high country.

“It’s a fun encounter when you’re hiking on a trail in the Rockies and a pika yells at you,” said Ray. “If you don’t have that anymore, your experience in the wild is degraded.”

Losing those small sounds would mark a real change for many people who feel connected to these peaks.

A hillside that once held a busy mix of adults and youngsters could turn into a quieter place, where older animals hang on but fewer young ones arrive. For scientists, that shift is important for what it says about the broader alpine system.

A shift that feels personal

Ray’s relationship with pikas goes back decades. Early in her career, in the 1990s, she met a male pika she nicknamed Mr. Mustard because of the yellow tags on his ears.

“He was an adult when I trapped him, and he lived for nine more years,” Ray said.

That kind of long life now seems rare at her study sites. “I don’t see that anymore, so I do think things are changing.”

For researchers who have spent much of their working lives with these animals, the shift is personal as well as scientific.

The study at Niwot Ridge adds a detailed case study to a larger picture: a warming West where even small, familiar neighbors on the rocks are feeling the heat.

The full study was published in the journal Arctic Antarctic and Alpine Research.

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