...how pikas can survive extreme conditions? (with Johanna Varner)

Ever Wonder? / September 13, 2023
PikaJo with pika
Image attribution
Courtesy of IF/THEN Collection
JoVarner holding Pika
Image attribution
Courtesy of IF/THEN Collection
Image attribution
Courtesy of IF/THEN Collection

In an earlier episode, we spoke with Johanna Varner (@johannavarner), also known as Pika Jo, Associate Professor of Biological Sciences at Colorado Mesa University. She introduced us to the pika – an adorable little creature about the size of a russet potato that lives high up in the mountains without hibernating in the winter!

Ever wonder how pikas can survive extreme conditions?

In this short we get to know more about this new known favorite critter and what they do to survive extreme conditions. Here is more of our conversation with Pika Jo.

Have a question you've been wondering about? Send an email or voice recording to the podcast team to tell us what you'd like to hear in future episodes.

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Karen Arroyo (00:06):

Hello, this is Ever Wonder? from the California Science Center. I'm Karen Arroyo. In an earlier episode, we spoke with Joanna Varner, Associate Professor of Biological Sciences at Colorado Mesa University. Joanna, also known as Pika Jo, introduced us to the Pika, an adorable little creature that lives high up in the mountains and survives cold winters. Some animals hibernate when it gets cold, but not pikas. Ever Wonder... how Pikas can survive extreme conditions? In this episode, Joanna shares how resilient pikas can be as they survive the alpine winter. She also tells us about some accidental research about how pikas survive a very different extreme condition: Wildfires. Let's take a listen.

Karen Arroyo (00:56):

Pikas depend on snow. And to me when you said this, this is surprising because I know that a lot of animals hibernate during winter, and to hear that pikas rely on snow shocked me a little bit. Can you explain why they depend on snow?

Johanna Varner (01:14):

Most alpine mammals kind of hibernate, and that's a really good way of surviving the winter when there isn't much to eat, right? You just fatten up in the fall, eat a lot of food when there's lots of food to eat, and then go to sleep for nine months and wake up again in the spring when the snow melts. But pikas is actually are incapable physiologically of hibernating, like their bodies can't go into that kind of deep sleep and lowered metabolism that other species can. And so what they have to do instead is they have to spend the short summer when there is lots of plants available. They eat mostly grasses and wild flowers that live in alpine meadows near the rocks where they live. And they spend their short summers collecting all of the plants that they're going to eat during the winter in addition to feeding themselves during the summer. And so a single pika can build this big, big winter food cache that's called a hay pile, that is about 65 pounds of food that it's gonna stash away in the rocks and pile up and dry out in the sun, and then store under the rocks. And that will be the food that it eats during the winter. So you could think of it as basically like having three months a year when the grocery store is open and having to go and find all of the food that you're gonna eat during the winter, during just three months in the summer, storing up your cellar with all of that food and then eating it in the winter without leaving your house. The reason that the pikas has really depend on the snow is because the snow actually acts like a layer of insulation and it helps to keep the temperatures that the pikas has experienced in the rocks close to freezing. So really close to about 32 degrees Fahrenheit. If you think about these mountain habitats, we oftentimes think about them being really cold. And so if you've ever gone to a ski resort or been up in the mountains, where there is a lot of snow, the temperature is usually in the winter, a lot colder than 32 degrees. But when you get this really thick layer of snow, it actually acts kind of like a blanket and helps to keep the temperatures that the pikas has actually experienced down in the rocks underneath the snow right there at freezing. So right at 32. And so ironically, with a thick snow pack when there's lots of snow, the pikas actually are warmer than in situations where they don't have very much snow and then they're exposed to those colder temperatures. So, I think one thing that's really amazing about pikas is how much energy they have to invest during the summer in order to collect all of that food that they're going to eat during the winter. So a single pika, in order to survive the winter, has to collect somewhere around 65 pounds of food. And if you think about a pika as being about the size and shape of a russet potato, that's actually a lot of food, even though 65 pounds may not seem like that much to us. So a single pika during three months during the summer, they have to make somewhere around 5,000 trips to the meadow out to collect grasses and flowers and then drag them back into their winter food cache, which we call a hay pile. And if you were to scale this into human terms, it would be like us collecting about 25,000 pounds of food, making 5,000 trips to the grocery store. And on every single one of those trips, you'd have to carry home the equivalent of about four heads of lettuce in your mouth. So the next time you're at the grocery store, I really recommend that you go spend some time in the produce section, check out the heads of lettuce, check out the potatoes, and I think that will really give you an appreciation for how much work these animals are doing in order to survive the winter.

Jennifer Aguirre (04:45):

For a second there, I thought you were gonna tell me to go stick four heads of lettuce in my mouth and walk out of the grocery store with them.

Johanna Varner (04:52):

I think you should try that too. That would be a really great experiential learning.

Jennifer Aguirre (04:57):

I'm a very visual person, so I'm picturing myself trying to like carry the heads of lettuce, that way.

Johanna Varner (05:03):


Karen Arroyo (05:04):

I can't imagine putting one head of lettuce in my mouth. So four is just unconceivable. I, I can't.

Johanna Varner (05:10):


Jennifer Aguirre (05:11):

Since pikas like the cold, how did they survive or how did it impact your research during the fires?

Johanna Varner (05:20):

Yeah, so unfortunately I probably have more experience studying how pikas respond to wildfires than anybody else just because of a series of really bad luck. I first, when I first started my PhD and I first started doing pika research, I was studying this really unusual population of pikas that lives close to sea level near the, just outside of Portland in the Columbia River Gorge. And I was trying to understand why this population of pikas was able to survive at such low elevations and in a habitat that gets really warm in the summer and doesn't have that thick, persistent snow cover blanket, to help protect them against winter cold temperatures or ice storms that happen there. And to do that, I kind of tried to set up a comparison with a more typical population of pikas that was living up on Mount Hood at, you know, close to treeline in this more typical habitat where we would expect to find pikas. And so I went out to these two different places. I tried to catch and mark the animals so that we could track their survival. And that was a whole other adventure, of a problem. But we put out temperature sensors, we did a bunch of vegetation surveys, and then we left. And I went back to University of Utah where I was studying, and I came back the following summer in 2012. And all of my high elevation sort of control sites had burned up in a massive wildfire while I was gone. And so, the first thing I did was I sat down and just started crying because it was so sad. The, you know, it was so sad. All of these really beautiful places that I had spent all of last summer were all, you know, totally charred. The fire was really severe in some places. All of the forest was completely dead. All of the grasses were dead. The saddest part was coming back to some of the, those winter food caches from our marked animals and finding those to be little piles of crispy ashes where we had spent the summer watching these little pikas building all of the food that they're going to eat for the winter. And then it all burned up. And my field crew wasn't really sure what to do with me because they didn't really know what was going on, except that I was having a little emotional breakdown out in the middle of nowhere. And when I kind of got over the initial sort of shock and sadness of this, we ended up trying to sort of reorient to try to understand how these kinds of wildfires, which we know are becoming more frequent and more severe across the American West and especially in places like California, how those kinds of fire regimes might affect this species that already has to face all of these other challenges that, I, that we already know about. And nobody had ever really studied that before. So we spent a couple days in a coffee shop in Hood River scouring the literature, trying to figure out how do people study fire, and how do people measure burn severity? And all of these other questions that I just had no experience with in my past. And coming up with some protocols to try to get a handle on, you know, the resources that were available to the pikas that we could track as the habitat recovered and ways to estimate population size of pikas, so that we could also observe that recovery process. So, that was kind of our first big study. One of the things that was really interesting and encouraging about that study was that the populations of pikas has actually rebounded fairly quickly. So within two years of the fire, every single one of the 20 different sites that we visited was occupied by pikas in at least one season of sampling. So they came back even to these really, really severely burned habitats pretty quickly. And they seemed to come back with a sort of threshold of vegetation availability. So it didn't really matter so much what plants were there, but it mattered more like how much plant material was there. And that's really cool from a conservation perspective because it gives our land managers some like targets, right? Like numbers. This is how much food it needs to be in a habitat to support a population of pikas. So that was kind of my first experience studying pikas and wildfire. Unfortunately, I had a second experience in 2017 with the Eagle Creek fire, which then burned up the low elevation populations in the Columbia River Gorge. And we've been working with a community science organization there called Cascades Pika Watch to help, engage people from Portland and from the Columbia Gorge and from Washington in helping to monitor that population recovery. And once again, you know, the kind of good news is that at least in that habitat, the pikas seemed to rebound pretty quickly. And so they definitely had kind of a decline in 2018, the year after the fire. But in 2019, their population went, you know, was much higher and they were found in a lot more places. Unfortunately that research was then derailed by Covid in 2020 since then. So, we're still kind of working on getting it restarted.

Karen Arroyo (10:24):

They're so resilient. Not only are they cute, they're also resilient.

Johanna Varner (10:28):

Exactly. They're cute and they're little survivors.

Jennifer Aguirre (10:31):

Yeah. They're very good at finding the environment they need to survive. Right? So like looking under rocks to stay cooler.

Karen Arroyo (10:40):

Eating whatever is growing.

Jennifer Aguirre (10:42):

I'm wondering if they sploot, Jo? Whatever splooting is. So whatever you wanna,

Johanna Varner (10:49):

Whatever splooting is.

Jennifer Aguirre (10:50):

Yeah. Um, so do they sploot?

Johanna Varner (10:54):

I actually had to go and look up what splooting means.

Jennifer Aguirre (10:57):

Splooting. Yes.

Johanna Varner (10:57):

Because it's not a term that we, that we use very often in the pika behavioral literature,

Jennifer Aguirre (11:03):


Johanna Varner (11:03):

But it's a delightfully descriptive term and I learned that lots of species of squirrels sploot. When an animal sploots, it means that it is laying out, and making, increasing its contact between its body and the ground or the surrounding environment, usually as a way of trying to dump body heat. So you could imagine maybe being outside in a really like hot day and in Phoenix or a really hot day somewhere in southern California, and you go into an air conditioned house and you just lay on the floor to try to cool off. And that is apparently what's splooting is. So as far as whether pikas sploot or not, the answer is we're still not really sure. We see this behavior occasionally in some places, but they usually when they get too hot and they need to cool off, what they do is they dive below the surface of the rocks down in sort of the spaces between the boulders and these big jumbled piles of boulder fields. And so we're not really sure what they're doing down there. I think there's a very high probability they may be splooting, but nobody has ever been able to place a camera in a place where we could observe that. For sure. So maybe that's an open line of research and I should write a grant on, to study pika splooting behavior, subsurface splooting.

Karen Arroyo (12:27):

And that's our show. Thanks for listening. Until next time, keep wondering.

Karen Arroyo (12:34):

Ever Wonder? from the California Science Center is produced by me, Karen Arroyo, along with Jennifer Aguirre, D. Hunter White, and Perry Roth-Johnson. Liz Roth-Johnson is our editor. Theme music provided by Michael Nickolas and Pond5. We'll drop a new episode every other Wednesday. If you're a fan of the show, be sure to subscribe and leave us a rating or review on Apple Podcast. It really helps other people discover our show. Have a question you've been wondering about? Send us an email or voice recording to [email protected] to tell us what you'd like to hear in future episodes.