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Down to Earth: Keeping the Wolverine Wild

After more than a decade of litigation, the federal government has finally proposed to protect wolverines as a threatened species under the Endangered Species Act. Down to Earth speaks with Douglas H. Chadwick, a wildlife biologist and journalist who wrote the book The Wolverine Way.


Douglas H. Chadwick is a wildlife biologist and journalist whose work appears regularly in National Geographic. His latest book is The Wolverine Way.

Doug Chadwick is a wildlife biologist and journalist for National Geographic. As a volunteer for the Glacier National Park Wolverine Project, Doug helped researchers track wolverines, fierce members of the weasel family who regularly face down grizzly bears and eat entire bones for dinner. Despite their ferocity, both climate change and trapping threaten the wolverines' existence.

Doug spoke with Jessica Knoblauch, content producer at Earthjustice, in Feburary of 2013.

Jessica Knoblauch: Doug Chadwick, welcome to Down to Earth.

Doug Chadwick: Well, thank you.

Jessica: So start by telling me about your first encounter with a wolverine.

How did you become interested in wolverines?

Doug: Oh, I was about sixteen, and I was in Alaska, and it was not a direct encounter with a wolverine. I was underground in a placer gold mine where the fellow telling us what he was doing—he looked like he had run into a Cuisinart. And the story was that he trapped a wolverine and he clubbed it in the head. And then to carry it back to camp he tied the paws, bound them together, and then looped them over his head and started back to camp. And as you can probably guess, it turned out the wolverine wasn't dead. Anyway, that was my first, "That was a wolverine? A wolverine did that? Oh my god! They're everything people have said they are and even worse."

My next encounters were while I was studying mountain goats up in the high country of Glacier [National] Park in the Bob Marshall Wilderness in Montana. And I would see wolverines occasionally, and they were lovely, they were free, and they covered the ground like nothing I'd ever seen. But they also tore up a couple of my tents and pulled every single goose feather out of a couple of sleeping bags just to see if there was any meat to go with the feathers. So I didn't know what to make of them!

With that background, I heard there was a research project starting up in Glacier Park. And Glacier Park, I lived close to it. And being a wildlife reporter and a conservationist I said, "I just gotta go meet these guys and spend some time with them. Maybe I'll finally learn a bit about wolverine biology."

[The wolverine way is] climb everything, whether it’s trees, cliffs, avalanche chutes; eat everything whether it’s small, large, alive, dead; and never back down, even from a mountain and least of all from a grizzly bear.

I went in through a snowstorm, skied into the east side of the park, met these people in the backcountry and started following wolverine tracks and listening to beats on a radio receiver because they had some radio tagged. But I still wasn't seeing a wolverine, and yet the stories they were telling me of how much ground these animals covered in a 24-hour period and secondhand tales of wolverines standing off much bigger carnivores over a carcass, including grizzly bears, and pretty soon I found myself getting really hooked.

And then I went down later in the year with another researcher down a trail just below the Continental Divide, and I looked up and saw him waving at me kind of frantically to come down the trail. I trotted down and about 25 feet away was a mother wolverine with two young and they were standing in the middle of a wildflower bouquet lapping water out of a high mountain stream. And then they started playing together. I thought, "Wow, this is a pretty magnificent animal." I was just sitting there on top of the world with these three rare creatures. It just went on from there.

Jessica: Most people have never seen a wolverine. In fact, they're only familiar with the name "wolverine" because of, you know, the X-Men comics. So I mean, why do we know so little about these creatures?

Why is so little known about wolverines?

Doug: [Laughs] Yeah, and I love Wolverine [of the X-Men]. He's great. He's got ten-inch claws made of adamantium, and they can slice through helicopter rotors. I mean, that's a pretty good superhero.

Until we had GPS technology, I just don't know anybody alive that could keep up with a wolverine for 24 hours. They don't go incredibly fast. They just go constantly, day and night, and with brief intervals of rest in between. These are 30 pound animals. They're three feet long, a little more if you count their tail, and yet they have home ranges the size of a grizzly bear. So we're talking four to 500 square miles for males, and about half of that for females, and this is right on top of the world. I mean, they're going up peaks and through passes and along cliff faces. I would brag about it for months if I went one-tenth of the distance they traveled in a day.

So that was the big eye-opener is how much ground they cover. And then the other part of this is they're strictly territorial. So that means you can't fit very many of these wide-ranging animals into any one spot. And even a place as big as Glacier Park, which is 1500 square miles has, let's just say, between 30 and maybe 45 wolverines. That same park has an estimated 340-some grizzly bears living in it.

Close Video

The Wolverine Way

From Patagonia Books comes a story that goes inside the fascinating history of the elusive creature known as the wolverine—and the threats that face them today.

Written by wildlife biologist and and Vice Chair of Vital Ground Douglas H. Chadwick, The Wolverine Way describes the challenges and surprising discoveries uncovered while studying the animals as they roam across the Continental Divide.

This video preview was produced by Wild Collective.

You can put an amazing number of bears into this space, but in that same great mountain expanse, you can't have a genetically varied, viable, long-term population of wolverines. And so that tells you something very important about wolverines, which is you need connections between existing wildlands. And the way they're going to persist is as what biologists call a meta-population. You're going to have a handful here. You're going to have a couple dozen there, miles and miles away. And they have to be connected to one another for the population as a whole in western U.S. to endure over time.

And that's a pretty startling concept because it tells us we need to go about conservation a bit differently. We can't just go out and say, "Oh, we've set aside this mountaintop here and this little range of mountains over here, and so we protected nature." And the wolverine's reminding us of something that really applies to almost all the big wide-ranging animals. That was the first step in conservation, but the next one is to link them together so genes can flow across the landscape; animals that are reduced in one area can be replenished by a population somewhere else. So if it's big and connected, this will work. If it's a series of isolated little reserves, it won't work.

And the other thing about the scale of movements, it's not only huge, but it's constant. They're always on the go. And so what was happening through the years was people would see tracks when they went out and did surveys, and they said, "Oh, well I think we've got a fair number of wolverines here." We now can go out and say, "Yeah, all those tracks you saw in 10 different mountain drainages you went through, that's one male."

There are only an estimated 250 to 300 wolverines south of Canada, and they are spread in a series of small populations, and that makes this a uniquely vulnerable critter. Wolverines live in the very tip top of this country, and they're tied to deep snow and year-round cold. They can handle the high country with their big feet and their exceptional fur and their high metabolism better than anybody else, so that means they don't have much competition for this niche they've chosen in the Alpine and sub-Alpine, but there's not much food up there either. And that's probably why they're covering such and defending such immense territories is, you can have it all to yourself but boy, you have to be able to cover the mountains like crazy to find enough food, especially over winter.

Jessica: I've heard they can eat everything. Can you speak a little bit to that?

Describe the wolverine's famous appetite.

Doug: You look up in those high ridges and those high slopes and say, "Wow, a wolverine just floating over the snow with its big feet. It's covering all this ground, but what the heck is up there?"

I mean, there is plenty of wildlife in the Rockies. It's just that it's down on south-facing slopes. It's migrated far enough down the valleys to a more snow-free area. The big game ranges are quite a distance, usually, from where the wolverines are. And so what are they living on? And the answer seems to be food they have cached during the warm months when the big critters were up in the high country and maybe something they killed and maybe something a cougar killed, a wolf killed, a grizzly killed months earlier.

"If we’re going to keep these animals, they need every break we can give them. And there's still the need for a lot more information."  (Outdoor NE)

And the wolverine has carried off pieces of it and cached it in snow banks during the summer or maybe put them under boulders that have cold water running under them. So it's got food stored in all these natural refrigerators, and it can come back six months later in January or February when a female is denning up there to create a den for the birth of her kits. And then she can leave and go these areas where she stashed food earlier, and she can not only eat the kinds of things we can imagine, but she can crunch up the bones. They have very strong jaws, a terrific bite force on them. And we would find autopsied wolverines whose stomachs felt like they were full of gravel because they were just a big rubble of bones.

This is a consummate scavenger. They can grab a squirrel, a ptarmigan, a snowshoe hare on the way. They can climb trees and get at other food. They swim with their big paws. They've been seen chasing ducks and fishing. They eat berries. They do what they have to do to survive. So if you can cover several hundred square miles and eat virtually everything you come upon, and you've got the attitude to walk up to a carcass that has a grizzly on it, or a couple of wolves, or a cougar and go, "This is mine now." And the other animal says, "Wait a minute. You're only three feet long." And then you start issuing this wolverine growl that sounds kind of like a Harley Davidson mating with a chainsaw. It's really velociraptor-quality stuff.

Jessica: They sound really just scrappy and ferocious.

What are wolverines really like?

Doug: They are scrappy and ferocious. There are lots of stories of how they would attack people and they were destructive and a danger to the lone mountain man in the backcountry. And no one's ever been able to trace down a true story of that. What we were finding was they actually have some family structure.

But if you do corner one in a trap, they turn into the wolverine of myth. I mean, they are just, holy smokes, they're a dynamo. It's like caged plutonium in there. These things just keep coming at you, and they're growling. They've got saliva coming out of their mouth. And so you can kind of see where some of this comes from, and you can see that for years, what we knew about wolverines came mostly from trappers.

Log box-trap in Glacier National Park. The traps were used to temporarily capture wolverines to obtain survey data.  (Wolverine Population Assessment in Glacier NP)

So if you come up on a wolverine that's been in a trap for a couple of days with tremendous pain. Just picture yourself there, and then some guy comes up and intends to club it on the head and take its skin, and then, what a human thing that is to say. "Wow, this is a nasty, vicious animal" [Laughs] Okay, I would be, too!

Anyway, we make animals into kind of what we want them to be. We like dangerous critters, and carnivores are supposed to be naturally surly. But what we were finding was males associating with their young after they became independent and some of the supposedly independent ones going back and associating with mom. Not a lot, but they were tolerated. The big part is they're also allowed to stay in the parents' territories after they become independent, so that means they can follow dad around or follow mom around, see where they're going, where they're hunting, where the food is.

And equally important, they don't have to defend a territory against larger, more experienced wolverines until they're almost two years old and ready to head out on their own. In this tough environment, their chances of survival go way up because they do have continued family relationships for a couple of years. And who knows what else we'll discover?

One time I was doing a story for National Geographic on endangered species, and I went to a place where they were breeding red wolves in captivity, and somebody said, "Do you want to come and see something interesting?" And of course, yeah I do, lead the way. And he leads me to about a half-acre pen, and there's tons of wolverines inside.

And then he says, "Do you want to go in?" And I'm thinking, "No." [Laughs] From what I've heard about wolverines, a herd of wolverines is not something I want to walk into. But we did go in, and these guys are rolling around together like puppies and playing with each other in big furry balls. And then they all come scampering over to see us. And they're tremendously inquisitive, and they explore you with their little nips and sniffs in your ear.

"They're not afraid of anything. They climb peaks that human climbers turn back from. So they're just fearless, and they're tireless, and they got no end of attitude."  (Dale Pedersen)

They were tremendously social. So right then, before I got involved with the Glacier project, I said, "Wow there's definitely a lot more to these critters than I've heard from all the old frontier tales, but I don't know what it is. Let's go find out."

One reason I was kind of eager to find out more about them was, like so many animals, the more we know about them the more the old image changes, and they turn out to have dimensions we never guessed, and they turn out to be way more fascinating.

My life is simple. If someone can teach me new things and show me new aspects of nature, I'm in. If I got any spare time, I'll help out and learn along the way. After doing that, my other role is as a journalist. I just wanted to get these guys up on the radar because you realize they're not going to hold up. It's tough enough to survive on the southern end of their range. They tend to be in scattered little populations in separate mountain ranges, and you know they've got to contend with bigger predators; they've got to contend with winter on top of the Cascades. And on top of that, they've now got to deal with human impacts, and they've got to deal with climate change.

The more we know about them, the more the old image changes, and they turn out to have dimensions we never guessed, and they turn out to be way more fascinating.

Females require deep, persistent snowpack to raise their young from February through May, and they don't tend to tolerate warm temperatures very well. You won't find wolverines where the average summer temperatures get really hot, even in high mountains. And they need that deep, persistent snowpack also probably for caching their food. So as scientists have modeled this under various climate regimes, the best they can come up with in the future is that wolverines are going to lose perhaps a third of their existing range in the U.S., in the lower-48, by 2049 or 2050. And by the end of the century, they'll have lost almost two-thirds. So that means if we're going to keep these animals, they need every break we can give them, and there's still a need for a lot more information. It's typical where we finally recognize an animal is in tough straits and then we run out and try to learn about it.

Wolverine on the prowl in Glacier National Park. About 30 pounds heavy and three feet long, wolverines have been known to travel more than 20 miles in a day.  (NPS)

But I hope we can, and what we do know is that in a situation with shrinking ranges the connections between wild lands become all the more important. They can persist because they're great travelers. One has made it from the Tetons 500 miles down to Rocky Mountain National Park in Colorado, and one made it from it looks like maybe central Idaho 600 miles down to Lake Tahoe in California.

These are both dispersing young males. They need a date. They need to find a girlfriend, or we need to bring some down there. But they can persist if they have wild ways, or habitat bridges, or corridors, or whatever you want to call it so that these scattered populations can stay in touch with one another, and that we can provide. What to do about global warming, I think that's going to be a separate podcast for you.

Jessica: As I'm sure you've heard in February the U.S. Fish and Wildlife [Service], after years of conservation groups asking for this, they finally proposed that the wolverine be listed as a threatened species. So is it your hope that if they do get these protections, things like wildlife corridors will be established?

What can we learn from gaining endangered species protections for wolverines?

Doug: It is. Let's go back to climate for just a minute. When people hear about wildlife and climate change, I think the standard thing is, "Oh boy, the polar bear and maybe the caribou up in the Arctic are going to have a real problem." We think of the shrinking ice cap. We're not as attuned to it down in our midst, but now we've got an equivalent of the southern polar bear. We've got an animal very closely tied to climate, not in our midst in the sense of, you know, the deer in our yard but, in the Rockies, in the coastal ranges, that's telling us the same thing. And I think that's valuable in and of itself because every other critter from butterflies to, let's say ptarmigan or golden-mantled ground squirrels or mountain goats, they all are going to be affected by those same changes in temperature and snowpack and forests marching uphill, taking over the Alpine areas and all that.

So it's really good to have the wolverine here as a really intriguing animal that focuses our attention on that. And then it's good to have an animal that tells us we need to move past the 100-year old model of how we go about conservation, which is setting aside isolated parks here and there.

They're one of the greatest beasts we have to share these ecosystems. They're absolutely inspiring. They make the mountains taller. They make the whole place more alive, and we can't lose animals like that just because we're not paying attention.

They need these large landscapes. They need wild ways between them. We don't need to declare a lot more wilderness for this or that necessarily. We just have to keep the landscape permeable to wildlife, and the wolverine can help lead the way now. You have to remember, animals like grizzlies or wolverines, they didn't arrive in little isolated museum-like reserves. They arose in big sweeping landscapes with an interchange of genes and interacting predator populations.

You need a big, dynamic, natural system, so the question now is not how to preserve samples of it but how to preserve the connections that keep the whole thing vibrant. And so by protecting the wolverine, I think the Fish and Wildlife Service reinforced this next phase of conservation, which is thinking bigger and thinking more connected.

And this is a huge change because when the wolverine was first proposed for listing, it was turned down a couple of times just because the agencies would say, "We don't know enough." There's not enough information out there for us to say, 'yay or nay'." And it's just in the last couple of decades they've got enough information not only to start protecting the animal but to start getting a grip on what we need to do to keep it and a whole lot of other wildlife going.

Jessica: Right. Well, and as you said, people don't really come into contact with wolverines. So in some ways, I feel like it's hard for people to care about them, you know, because they don't really know anything about them.

How can we get the public to care about such a mysterious animal?

Doug: Yeah, and that's why I helped talk PBS into doing a special on them. It's called Chasing the Phantom, and then I did a book, The Wolverine Way, to get the word out on these guys. I think it's a shame to see a species possibly dwindle away just because no one's paying attention.

So that's been my job as a journalist and a scientist is to get them up on the public's radar cause they're an inspiring critter. They're one of the greatest beasts we have to share these ecosystems. They're absolutely inspiring. They make the mountains taller. They make the whole place more alive, and we can't lose animals like that just because we're not paying attention.

Jessica: One wolverine that I came across that you've mentioned in some of your writings is M3. Can you tell me a little bit about him?

Describe the wolverine known as "M3".

Doug: You got it, my hero, yeah [laughs]. I can tell you that M3 is the badass's badass. He is a big male. He was young when we got to know him, and he did not like being in the trap.

He is a beautiful animal, chocolate-colored with bronze stripes on his side. And as we were tracking him, he kicked out an older male in the territory north of him; he expanded his territory until it included a good part of Canada as well as Glacier Park. He was like the Genghis Khan of gulos. Gulo gulo is the scientific name [for wolverines]. I mean, he was just expanding his empire and taking over other wolverines' women and collecting all the power he could. I don't know what he was up to. He was just a big dominant animal.

Mount Cleveland, the highest peak in Glacier National Park. The legendary wolverine M3 summited Mt. Cleveland's sheer face in the dead of winter.  (Gene Sentz)

But in the course of doing all this, he climbed the highest peak in Glacier, 10,460 feet. And he did the last vertical mile in 90 minutes, up a rock face that looks like it's the world's steepest, longest ski jump. People subsequently tried to do what they called "The M3 Route." They went about a third of the way up and bailed.

And we had other wolverines that did similar exploits. We've also picked up the carcass of a wolverine that died crossing the steep cliff face, just fell off. So why are they doing this? What's the advantage? Why the risk? What's the reward that balances that? And that's going to have to get classified under the large unknown category in wolverines.

I really don't know why they do it, but I know they do it regularly, and I know it's a big part of their lifestyle to cross the kind of avalanche slopes and rock walls and steep chutes. That was one of the reasons I call them inspiring. If you can master the mountains like that, for someone like me who spends a lot of time in the mountains, they're my heroes.

Jessica: One final question, and you've touched on this a little bit, but in your most recent book, The Wolverine Way, you talk about the wolverine's approach to life. Can you describe what that is?

Describe the wolverine's approach to life.

Doug: It's basically climb everything, whether it's trees, cliffs, avalanche chutes; eat everything whether it's small, large, alive, dead; and never back down, even from a mountain and least of all from a grizzly bear.

I think they live life as fiercely and relentlessly as it has ever been lived, and that's probably a better way of trying to explain why I'm so enamored of them. You know personally, I can't imagine living in a world giving up animals like this, these great creations. And discovering things about their family life, and their inquisitiveness, and their capabilities, it just makes it that much more rewarding. What are we saving nature for if we can't keep critters like this?

Jessica: Well, Doug, thank you so much for your time.

Doug: Yeah, thank you for your time and for letting me babble on! You know, the wolverine wouldn't be listed [under the Endangered Species Act], I don't think, without the work of Earthjustice. I can't recommend you guys too highly. It all works together somehow. I do what I can on my end, and then I think what really gets their attention of course is a nice lawsuit by Earthjustice, so I thank you on behalf of my wolverine buds.

I think they live life as fiercely and relentlessly as it has ever been lived … Personally, I can't imagine living in a world giving up animals like this, these great creations … What are we saving nature for if we can't keep critters like this?

Jessica: Doug Chadwick is a wildlife biologist and journalist whose work has appeared in National Geographic. His latest book is called The Wolverine Way.

For more information about Earthjustice's work to protect endangered species like the wolverine, check out And to hear more Down to Earth interviews with environmental experts, check out

Ten Things to Know About Wolverines:

  1. Wolverines are the largest members of the weasel family.
  2. The wolverine's scientific name, gulo gulo, means "glutton" in Latin.
  3. Wolverines are opportunistic eaters. They will forage, hunt, scavenge and even steal for food, traveling up to 15 miles in a day.
  4. Thanks to razor-sharp teeth and powerful jawbones, wolverines can crunch up entire bones of other animals.
  5. The wolverine's fur was once highly popular for lining the insides of jackets.
  6. Wolverines' giant paws, which are disproportionately large and wide for their body, allow them to walk on top of snow.
  7. Wolverines have an average life expectancy of only 4 to 6 years.
  8. Female wolverines require deep snowpack in order to birth and nurse their young in snow dens.
  9. Currently, there are no more than 300 wolverines left in the contiguous United States.
  10. Climate change may cause wolverines to lose two-thirds of their habitat by the end of this century.


Magazine Feature
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Tim Preso isn't likely to square off against a grizzly bear—as wolverines do—but he's figured out how to use the persistence and determination of a wolverine to keep it from going extinct in the continental United States.

Interview: Down to Earth
Climate Change in Glacier National Park

Research ecologist Dan Fagre discusses how climate change in the Crown of the Continent could result in a glacier-free Glacier National Park by 2030.

Down to Earth, an Earthjustice Podcast

Down to Earth is an audio podcast about the news, events and personalities that make up Earthjustice. Hear from attorneys, clients, scientific experts, and more on Earthjustice litigation.

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Office:  Northern Rockies
Program Area:  The Wild
Formatted Quote: