Wolverines are vicious killing machines that are afraid of nothing. They are notoriously elusive and difficult to study. They look great without a shirt on.

Yeah, you probably don’t want to be locked in a cage with a wolverine (unless it’s Hugh Jackman). But killing machines? While wolverines are cunning carnivores, they are as likely to be playful, nurturing, and at times overcome by behaviour-altering fear.

In my former days as a biologist in the Yukon Territory, Canada, one of my colleagues came back from work one day and told me he had seen a wolverine riding on the back of a terrified deer.

The wolverine ripped flesh from the deer’s shoulder blades as the deer, eyes bulging, frantically tried to dislodge the spitting, hissing weasel from it’s back. The deer was not successful, and eventually collapsed in a fit of shock, hopefully unaware of the sharp teeth closing in on its spine.

Move over weaselpecker – it’s the wolverdeer.

They feel they can’t linger

Accounts like this are the stuff of horror films, or perhaps X-men movies, where Marvel’s troubled, leather-clad badass, Wolverine, eviscerates his enemy with metal spikes that shoot implausibly from his metacarpals. It’s hard to be sure where he hides these steak knives when he’s not cutting up villains (real wolverines don’t have retractable claws), but any way you slice it, Wolverine has a reputation as a borderline sociopathic killer.

The reputation of the wild version that inspired the movie character is not much better.

Face off

Wolverines are ferocious killing machines, yes, but there’s also some evidence that their hissy fits are just for show - a demonic display performed not as a precursor to a good lashing, but simply to scare away the threat, be it a bigger predator or a human.

In short the wolverine often bluffs, exaggerating its fearsomeness.

Dr Jason Fisher a wildlife ecologist with Alberta Innovates Technology Futures and a member of the Alberta Wolverine Working Group, has seen this firsthand. While tracking a wolverine, he accidently cornered it in a spruce thicket. The spruce shook, hissed and screamed in a way that petrified him. Fisher stood his ground, and instead of attacking, eventually the wolverine backed away, shrieking the whole time.

In nature, body size usually wins out

Why develop such an amazing ability to bluff?

It turns out wolverines have a history of having to watch their back. “Their life history is one of a scavenging carnivore, which means they feed on carcasses that are out there on the landscape,” says Fisher, adding that wolverines aren’t the only ones wanting a piece of the decaying action. Wolves, black bears, grizzly bears, raptors and cougars also like to saddle up to any rotting meat buffet.

Weighing 20-40 pounds (9-18 kg), wolverines are much smaller creatures than most of the predators they share habitat with, and so, says Fisher, naturally they need to exercise some discretion. “In nature, body size usually wins out.”

Fisher has seen internet videos of wolverines facing off against bears, but usually it doesn’t come to a fight. Rather it seems to be a battle of wills, complete with wolverine temper tantrums. The wolverines win some and lose some, but in general it makes more sense to bluff than to actually fight with other predators. Sometimes, “they do get killed and eaten,” says Fisher.

Smash and grab

If Hugh Jackman’s Wolverine has taught us anything, it’s that beneath that rock hard, muscly exterior there is more to the mutant than sneering at enemies and ripping things apart. The same can be said for his wild, weasly namesake. Wolverines show surprising flexibility in their behaviours.

Fisher and colleagues designed a study during which they collected DNA and snapped photos of wolverines by baiting automatically triggered camera sites with a stinky, tasty, beaver carcass attached to a tree. Individual wolverines could be identified by their unique markings, especially their “chest patches” that let researchers know just who they were dealing with.

“Some wolverines get to a site, and they really take their time,” says Fisher. “They sniff around, they might sit down, have a look about, and then they’ll eventually climb up the tree and have a nibble. We’ve got great footage of wolverine siblings playing around.”

Some wolverines even took the time to “beat the hell” out of several remote cameras. Kerpow!

They are extremely sensitive, and if we want them on the landscape, we need to see past the myth

On the other end of the spectrum, says Fisher, there are wolverines that race in and out of a site. “There’s a smash and grab of the bait – they’re hitting it Ocean’s 11 style.”

The team found that the most diverse behavioral repertoire was found in protected areas, where they saw everything from the smash-and-grabbers, to the lazy-take-your-timers.

“But in heavily developed areas,” says Fisher, “we’re only finding those smash-and-grabbers, which suggests there’s some reason they feel they have to get in, and get out really fast.”

Their hunch is that hanging around sites visited or altered by humans is risky. “Clearly, they feel there is some sort of risk associated with these landscapes, such that they feel they can’t linger,” he says.

Although the reasons for these differences in behaviour between habitats has yet to be nailed down, it might have something to do with the wolverine’s sensitive side.

Seeing past the myth

Over an evolutionary history of having to avoid blows from grizzly paws and deadly nips from a pack of wolves, the wolverine has had to be wary, and it seems they extend this wariness to places where humans build things or spend their time.

Across their range, wolverines are influenced by human activity – things like snowmobiling, forestry, and oil and gas extraction. “We don’t yet know the reasons for this vulnerability,” says Fisher, adding that wolverines may need undisturbed areas to build dens and raise their young. “Alternatively, landscape development may increase competition or predation by other carnivores, such as wolves or bears.”

Like the wolverine, a complete understanding of this big weasel’s behavior is for now elusive. And, like the endless number of episodes involving Marvel’s wolverine, the mysteries of the largest weasel on the planet are still unfolding.

“We think of them as tough and ferocious, and incredibly resilient. You can do anything to Hugh Jackman’s Wolverine, and he’ll bounce back,” says Fisher.

“But that’s not what we’re seeing with real wolverines at all.”

“They’ve been wiped out of half the continent already, and where they exist currently, they’re under a whole range of threats. They are extremely sensitive, and if we want them on the landscape, we need to see past the myth.”

Tweetable truths about wolverines:

Wolverines can be told apart by the varied markings on their chest.
Wolverines weigh only 20-40 pounds, and probably don’t spend a lot of time wrestling other carnivores.
Unlike Marvel’s superhero, real wolverines are not resilient to human-altered landscapes.
Wolverines are killed and eaten by bears, wolves and other carnivores.