The Pika Paradox: Why a Warming Climate Is Making Colorado Too Cold for Its Toughest Survivor

NEDERLAND, Colo. — If you have spent any time above treeline in Colorado, you have met a pika, whether you knew it or not. It is the sharp, indignant eeep! from somewhere in a boulder field — a sound with no visible source until a palm-sized, round-eared ball of fur pops onto a rock with a mouthful of wildflowers, glares at you, and vanishes. The American pika does not hibernate. It somehow rides out a 12,000-foot winter awake, living off hay it dried and stacked all summer. It is arguably the toughest survivor in the high country.

Two recent studies suggest that toughness is running into a limit — and the way climate change threatens the pika is far stranger, and more revealing, than the headlines let on.

Not "fry." Freeze.

The story you have probably heard about pikas goes like this: they are cold-adapted animals built for the alpine, they cannot shed heat well, and a warming world will simply cook them off the mountain. That is true as far as it goes. Pikas are genuinely heat-sensitive — chronic stress sets in around 78°F, and older laboratory work found that body temperatures can become lethal after just a couple of hours above roughly 82°F. For an animal wearing a permanent down coat, summer is a real and growing danger.

But the "they'll overheat" version skips the more counterintuitive half of the science: a warming climate can also leave pikas to freeze.

Here is the mechanism, and it is the part of this story almost no one is telling. Pikas overwinter inside talus — those jumbled rock slopes — insulated not by the rock but by the snow on top of it. Scientists call the gap between the snowpack and the ground the subnivium, and it functions like a blanket. Deep snow traps the relatively warm air rising from the ground and holds the under-snow world at a stable temperature near freezing, no matter how brutally cold the air above gets. That stable pocket is what a non-hibernating, snack-sized mammal needs to survive January.

Take the snow away, and you do not get a warmer winter for the pika. You get a colder one. Without the insulating blanket, the talus is exposed directly to the deep cold of the open air, and the animals inside can freeze or burn through their fat reserves trying to stay warm. A landmark 2019 study in Nature Climate Change gave this paradox a name: as the climate warms and snow cover thins, many snow-dependent species will experience "functionally colder winters" — not in spite of warming, but because of it.

What the new Colorado-led research actually found

The reason this is news now is two studies, both led by Colorado researchers, both published in the last several months.

The first comes from the Niwot Ridge Long-Term Ecological Research site, a stretch of tundra and boulder-strewn hillside about 10 miles south of Rocky Mountain National Park, north of Nederland. Researchers have tracked pikas there since the 1980s. In a study published October 31, 2025, in the journal Arctic, Antarctic, and Alpine Research, University of Colorado Boulder biologist Chris Ray and co-author Jasmine Vidrio integrated decades of survey data and found something quietly alarming: the share of juvenile pikas being trapped at the site has fallen by roughly 50% since the 1980s.

That figure is about recruitment — the rate at which young animals are born into, or migrate into, a population to replace the old ones. A 50% drop does not mean half the pikas are gone today. It means the population is graying: increasingly dominated by older adults, with too few youngsters coming up behind them. That is the demographic signature of a population running out of runway.

The second study, published in 2026 in Western North American Naturalist, comes from a Colorado Mesa University team — led by recent CMU graduate Karli Weatherill, with longtime pika researcher Johanna Varner as senior author — studying an isolated pika population in Utah's La Sal Mountains. Surveying the same animals from 2018 to 2023 and measuring stress hormones in their droppings, the team found that pikas showed higher population-level stress in years with hotter August temperatures. Different mountains, different method, same direction: the heat is wearing on them.

Here's the honest part: scientists can't yet say which threat is doing it

This is where responsible reporting has to slow down, because the easy version of this story overstates what we know.

The freeze mechanism is real and documented — but most of the hard evidence for pikas actually dying of cold comes from places that have lost snow, like Washington's North Cascades, where a low-snow winter in 2014–15 was followed by pika die-offs at the lowest, least-insulated elevations. Niwot Ridge, crucially, has not lost its snow cover. What it has seen is clear summer warming. So at Niwot specifically, Ray has been careful to say heat is the more likely local driver — and that she cannot yet pinpoint the cause of the recruitment decline at all.

So why does the freeze paradox matter for a Colorado story if it may not be what's happening in Colorado? Because it is the live hypothesis that ties everything together — and because the bridge between heat and cold runs straight through the animal's daily life. A pika that spends a hot summer hiding in the cool talus instead of foraging builds a smaller hay pile. A smaller hay pile means less fuel to burn through the next winter. Research in the North Cascades found that after a low-snow winter, surviving pikas didn't just struggle — they failed to reproduce the following year. That is exactly how you would produce a "recruitment collapse" without a single dramatic, visible die-off. The animals don't vanish in a bad winter. They quietly stop replacing themselves.

Heat in summer, cold in winter, food in between — for the pika, these are not separate problems. They are one problem with three faces.

Why a two-ounce rabbit relative is worth your attention

Pikas are what scientists call an indicator species: because they live in such a narrow band of conditions, their health is an early read on the health of the whole alpine system — the same high-elevation snow and ice that, as Ray puts it, functions as Colorado's "water tower," feeding the reservoirs we all depend on downstream. When the pika struggles, it is telling us something about the mountains far beyond itself. (For the bigger picture on what's shifting across the state, see our summary of the Climate Change in Colorado report.)

And the pika's predicament has a particular cruelty to it: it cannot simply climb higher to escape the heat. Mountains narrow as they rise. Move a population upslope far enough and it eventually runs out of mountain. Colorado's pikas are currently considered stable — the concern is the trajectory. One widely cited National Park Service modeling effort projected that pikas could be effectively gone from Rocky Mountain National Park by the end of this century under unchecked warming.

Despite all of this, the American pika still has no federal protection. The U.S. Fish and Wildlife Service declined to list it under the Endangered Species Act in 2010, and declined a second petition in 2024, both times concluding the case was not yet strong enough. A recurring theme in those decisions: not enough data on population trends. Which leads, conveniently, to the one part of this story where you are not a spectator.

What you can actually do above treeline

Start by learning to notice them. Once you know the signs, you will realize pikas have been all around you on every talus-edged trail:

• The call: a high, nasal eeep! or bark from the rocks — usually an alarm aimed at you.
• Hay piles: small bouquets of drying grass and wildflowers tucked under or between rocks. That's the winter pantry.
• Sign on the stone: whitish urine stains and small, round scat on prominent talus rocks.

Then give them room. Pikas are working against a deadline all summer, and every minute spent fleeing a hiker or a loose dog is a minute not spent gathering the food that has to last until June. The Leave No Trace move here is simple: keep your distance from foraging pikas, never disturb a hay pile, and leash dogs near talus fields. (Our general guidance on encountering wildlife responsibly applies here, and it's the same restraint we ask for around larger animals like moose.)

And here is the part that closes the loop on that "not enough data" problem. The Colorado Pika Project — a partnership of Rocky Mountain Wild and the Denver Zoo Conservation Alliance — turns hikers into data collectors, and the data feeds directly into the research that informs land managers and listing decisions. The program won Rocky Mountain National Park's Community Science Award in early 2026, so it is very much active. You can plug in two ways:

• The easy way: download the free Pika Patrol app (iOS and Android) and log any pika sign you spot — call, hay pile, scat, or the animal itself — wherever you happen to find it. No training required; the app teaches you the signs.
• The committed way: become a trained Pika Patroller, attend a half-day summer training, and adopt a long-term monitoring site on the Front Range, in Rocky Mountain National Park, or in the White River National Forest.

Both options are at pikapartners.org. In the Southern Rockies and San Juans, the Mountain Studies Institute runs a parallel program called PikaNet.

The pika has been telling us about these mountains for forty years, in a language of squeaks and hay piles, and for most of that time almost no one was writing it down. The science is finally catching up. The next data point could be yours.