Last winter was rough in Montana. How did wildlife fare?
Austin Amestoy: Welcome to the Big Why, a series from Montana Public Radio where we find out what we can discover together. I'm your host, Austin Amestoy. This is a show about listener-powered reporting. We'll answer questions, big or small, about anything under the Big Sky. By Montanans for Montana, this is the Big Why.
Today we're with reporter Ellis Juhlin.
Ellis Juhlin: Hey, Austin.
Austin Amestoy: We're switching gears from this hot summer, and cooling things off with an episode about last winter.
Ellis Juhlin: Yeah, that's right. This question comes to us from a couple of PhD students studying wildlife.
How did the extreme winter in and around Yellowstone affect animals like deer, elk and bison?
Ross Hinderer: My name is Ross Hinderer. I'm a graduate student at the University of Montana. I generally look at how amphibian populations grow.
Matt Webster: I'm Matt Webster, and I study how beavers influence aquatic communities in prairie streams.
Ellis Juhlin: Now, full disclosure one of these grad students is my fiancee, Matt. But being engaged to a public radio reporter, he knew that the Big Why was the right place to go to get a question like theirs answered. Their questions started as they were chatting about their respective field seasons out in eastern and northwestern Montana.
Matt Webster: We were talking about kind of this past winter and spring and how that's affected our study animals.
Ellis Juhlin: And they got to talking about some news they heard out of Wyoming: massive die offs of certain ungulates because of the elements last winter.
Austin Amestoy: Ungulates?
Ellis Juhlin: Yeah. So basically animals with hooves, like deer, elk, bison and pronghorn. But hearing this news, Matt and Ross got to wondering about those harsh conditions around Yellowstone.
Ross Hinderer: And how that might affect things in Montana that we haven't really heard much about.
Ellis Juhlin: So they wanted to know how did the extreme winter in and around Yellowstone affect animals like deer, elk and bison?
Austin Amestoy: Interesting. I haven't heard much about an ungulate die-off in the Yellowstone region, but for that to happen, I am betting we're talking about a lot more than just cold temperatures.
Ellis Juhlin: Yeah, we definitely are. From hunting to food chains to snowfall and temperatures and even entire ecosystems. Everything is so interconnected here. A good starting point is understanding what last winter was like in and around Yellowstone National Park. So, I went to the wildlife biologists who've been studying these animals and working in this system for decades. Julie Cunningham from Montana Fish, Wildlife and Parks and Dan Stahler from Yellowstone National Park. And they're going to be our guides through this whole web.
Julie Cunningham: The snows were so thick and so long, they came early and just stayed. And there is no respite for the for the critters.
For the last 23 years, it was our biggest snowfall that we had recorded, particularly early winter. Winter came fast and furious early in the season with a lot of snow accumulations and a lot of cold temperatures.Dan Stahler
Dan Stahler: For the last 23 years, it was our biggest snowfall that we had recorded, particularly early winter. Winter came fast and furious early in the season with a lot of snow accumulations and a lot of cold temperatures.
Ellis Juhlin: Austin, have you ever walked through deep snow? Like thigh deep or more?
Austin Amestoy: Not very successfully, I'd say.
Ellis Juhlin: Yeah, exactly. So, imagine putting yourself in the body of an ungulate. Now you've got four legs and you have to move those around through this deep snow. And every step is exhausting. You're slogging through several feet of snow just to make a little bit of progress. And you're hungry, but there's next to no forage exposed. So you have to dig down under all of that snow to try and reach anything to eat. Plus, when the occasional warm day hits and things melt a little bit, the deeper snow refreezes as a layer of ice that can be pretty much impossible for you to break through. So this means those ungulates like deer and elk and bison are burning through all of the energy they have just searching for food. And it's not enough to sustain them, so they're also burning through fat reserves. And for a lot of animals, those fat reserves just weren't enough to make it through this winter. When an animal succumbs to the elements like this, Dan explained to me that it's referred to as winter kill.
Dan Stahler: And this year we definitely had a notable increase in the amount of winter kill that we were detecting from our normal monitoring.
If ungulates are having a harder time moving around, are predators having an easier time catching them?
Austin Amestoy: Huh, interesting. But, Ellis, when I think of Yellowstone, I also think of predators. How did they affect ungulates this last winter?
Ellis Juhlin: You know, I wondered that, too. If ungulates are having a harder time moving around, are predators having an easier time catching them? Julie said she could see this play out in the case of Pronghorn antelope in the region.
Julie Cunningham: Pronghorn run to get away from predation, but the heavy or deep snow impedes their ability to run. It's easier for the coyotes to catch them.
Ellis Juhlin: And Dan watched this happen with wolves in Yellowstone, too. But he said it's not that simple. This predation is within the bigger picture of the climate this past winter. With their food buried underneath deep snow and their bodies working harder to stay warm, ungulates were just in poor health overall making them more likely to die or more easy to catch.
Dan Stahler: Despite carnivore abundance and diversity here in Yellowstone, there are a lot of animals that just were not being killed by predators, they were being killed by winter.
Austin Amestoy: Right. So, heavy snow led to poor eating for ungulates and good eating for carnivores. Did the elk and deer try to find a way out of that snow?
Ellis Juhlin: Yeah, they did. Every year as fall transitions into winter, many animals move to lower elevations where the snow is shallower, so it's easier to find food. For animals in Yellowstone, this often means moving outside of the park.
Julie Cunningham: On the west side of Yellowstone, we had some pretty good snow come early. By that I mean October.
Ellis Juhlin: Julie said when that happened, tons of ungulates headed outside the park. But the thing is, when they leave Yellowstone's boundaries, they don't have the same protections.
Julie Cunningham: That helped influence hunting season success because it moved animals to winter range during October and November, which is our general rifle season.
Ellis Juhlin: Julie said hunters shot 150% to 250% more elk than average in that hunting district this year. And that early movement was true for an even bigger ungulate. The park's iconic bison.
Dan Stahler: We had the greatest number of bison ever documented in the history of the park migrate out of the park at the north entrance.
Ellis Juhlin: That hunt was huge too. You might have heard about it since it made headlines all over the country.
Austin Amestoy: Wow, I had no clue there would be so many factors at play here. Between the deep snow, the hard to reach food, the human and predator hunting. Ellis, do we have any way to know how many deer and elk or bison died this winter?
Ellis Juhlin: So, the biologists I talked with don't go out and count carcasses one by one. But they did have some really interesting observations from the field this spring that gives us some insights into mortality numbers. Like in Yellowstone watching wolf packs they saw some really interesting stuff.
We had the Mollie's pack not make a single kill in over 30 days because they didn't have to because they were just finding winter kill bison.Dan Stahler:
Dan Stahler: We had the Mollie's pack not make a single kill in over 30 days because they didn't have to because they were just finding winter kill bison. And so that was the first time that we've ever documented a wolf pack not making a single kill in the month of March. And we've been doing these March winter studies for the last 28 years.
Austin Amestoy: Wait, to be clear that wolf pack didn't have to hunt at all during March? It fed solely on carcasses?
Ellis Juhlin: Yeah, exactly. By all accounts, there was winter kill all over the area. So, it was kind of like an all you can eat buffet for the wolves. So, there are certainly drops in these populations from this winter, but it's not all bad news.
Austin Amestoy: Okay, what's the upshot?
Ellis Juhlin: Well, in the short term, the females that give birth to the next generation seemed to have survived the winter pretty well. And Dan and Julie told me that the plants were glowing green when I talked to them after this wet spring. And all of that lush new food set up ungulate populations to get healthier going into the summer.
Julie Cunningham: I don't see any reason to be worried about their future in the long term.
Austin Amestoy: It's pretty remarkable just how durable these critters are. Ellis, do we have any idea what's next for them?
Ellis Juhlin: Well, just like the complexities of this winter itself, there's a lot that depends on the future, as in what the next several winters are like. Plus, everything that goes on outside of winter. Like the heat that we're in right now. It's left me with all kinds of questions about what that might mean for these animals that I'd love to ask Dan and Julie about.
Austin Amestoy: Well, thanks so much for coming on the show and sharing your reporting, Ellis.
Ellis Juhlin: Thanks for having me.
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