Chirping, charismatic pikas have perfected a cute-and-tough reputation for thousands of years, hoarding flowers in the frigid talus above treeline over long winters, then scampering miles to replenish food stores under piercing summer sun.
But the rabbit-cousin pikas have evolved a delicate metabolic sensibility: Above 76 degrees, their insides stress out. That’s why pikas dart back under rocks after you hear them but before you can see them, returning to the nurturing cool between boulders that one researcher calls steadier than a laboratory thermostat.
And now there’s more proof that the ravages of warming from climate change threaten the pika’s very existence in the Rocky Mountains.
New research from a team led by University of Colorado wildlife biologists in Boulder found a 50% drop in juvenile pikas captured over time in regular surveys on Niwot Ridge, north of Nederland and south of Rocky Mountain National Park. That means the adolescent pikas are not surviving their natural flight from nesting grounds to “recruit” into their own lifetime territory. Rising temperatures make the rocks and meadows too hot.
The study published in the journal “Arctic, Antarctic, and Alpine Research” is some of the early confirmation of long-held predictions that the popular pika will be one of the first high country species in noticeable decline from Colorado warming. Past research has predicted pikas might disappear from their narrow survival bands in the Rocky Mountains entirely by the end of the century.
Annual pika-sighting surveys by hundreds of volunteer hikers have sent similar warnings, with the creatures no longer seen at some lower elevations where they used to thrive.
“Our findings certainly suggest the need to consider that pika populations might soon be lost from some locations in the southern Rockies,” the new study says.
There’s no jump-starting evolution
The evolved just-right metabolism of pikas means they have a high resting body temperature in order to survive the winter without needing to hibernate, said CU Boulder research associate Chris Ray, who co-authored the current study. Problem is, “during the summertime, they’re very sensitive to heat, meaning they can’t actually survive for a few hours at anywhere above about 76 degrees.”
“Pikas are good at using a microclimate that is ridiculously stable,” Ray said. “The temperature in a good pika territory will look more stable than the temperature in one of the laboratories here at CU. It’s really amazing how these taluses work.”
That same perfected metabolism also makes it harder for them to simply adapt to new mountain homes.
So when a young pika strikes out on its own, “it’s got to move across a landscape that doesn’t contain talus to find another talus patch, and the more time it has to spend on south facing slopes and at lower elevations to find the habitat it needs, the less likely it is to make it,” Ray said.
In pika world, “recruitment” means the act of a juvenile staking out its own territory for life. When the pika traps show far more aging adults than healthy juveniles, sirens go off.
“Over the past forty years, American pika recruitment appears to have plummeted more than 50 percent in at least one study site at a core of the species’ distribution,” the study authors write.
“Juveniles are not coming in and claiming these empty territories,” Ray said, in an interview Wednesday. “It looks, unfortunately like the demographic data is supporting our dire prediction for Rocky Mountain National Park.”
Evolutionary adaptation for pikas — animals with an arbitrary genetic mutation that gives them a body characteristic less vulnerable to high temperatures — would take thousands of generations, if not longer, to become dominant. Pikas born with thinner fur for daytime adaptation would still freeze during plummeting nighttime temperatures, Ray said — they need the fur. For pikas to become nocturnal to take advantage of cooler nighttimes would require entirely new eye structures, bigger like rabbits and hares.
Even more worrisome, Ray said, is other research she and colleagues are involved in that puts temperature sensors down inside the talus and compares it to past temperature logs. “At one place on Niwot Ridge, we see that the temperatures in that microclimate have actually gone up more than the temperatures in the free air,” Ray said. “That was astounding to us.”
Ray said she fully understands why Colorado hikers are closely tracking the fate of the petite pika.
“I’m definitely one of the many who enjoy hearing their chirps and seeing them with a mouthful of flowers heading toward their hay pile when I’m hiking on trails in Colorado,” she said. “I definitely love that part, and I think that our enjoyment of many trails in Colorado would be greatly diminished if the pika has disappeared, or even if they went nocturnal.”
Rather than despair, though, she’s doubling down on the possibilities of research.
“I try not to worry, but what’s going to happen to these really incredible creatures that survive incredibly harsh conditions? 24/7, they’re on top of the mountain. We go home and crawl into a warm bed, you know, and they’re somehow surviving up there,” Ray said.
“And what makes them be able to survive the conditions that we perceive as harsh, cold conditions, is precisely what makes them vulnerable to the warming conditions, and I’m just more and more interested in what’s going to happen. So I’ll just keep studying this for the rest of my life.”