During summer months, the mammals feed on vegetation, but when snow blankets the landscape and temperatures plunge to 30 below, hungry hares scavenge other hare carcasses, as well as several species of birds. (See "Friends For Dinner: Why Some Animals Become Cannibals.")
And, in an ironic twist on natural selection, hares also dine on dead Canada lynx—their main predator, says Michael Peers, a Ph.D. candidate in ecology at the University of Alberta in Edmonton, who led a new study on the phenomenon in Bio One Complete.
“It was shocking to see the first time,” says Peers, who believes the hares are boosting their protein intake during harsh times. “I had no idea they actually scavenge.”
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Peers discovered meat-eating hares by accident, after setting up remote trail cameras next to hare carcasses near Mount St. Elias on the Alaska border. He expected predators to drop in and pick at the free offerings. Instead, two-and-a-half years of footage revealed hares ate from 20 of 161 carcasses observed.
The surprising images suggest animals aren't so easily classified as herbivores or carnivores—and that snowshoe hares are eating meat on a regular basis.
Feathery foods
Scientists have documented hares eating meat—and their penchant for violence—as far back as 1921, but those reports were anecdotal field reports, and this is the first time meat-eating has been caught on camera, Peers notes.
Other scientists have come close. In 2010, while studying mammal populations for the province of Ontario, biologist Kevan Cowcill set up cans of partially opened sardines throughout the boreal forest. Instead of wolves and martens plucking the pesce, his camera traps captured hares.
“They'd stand up on their hind legs, and pull the sardines out of the can that was nailed to the tree,” recalls Cowcill, who didn’t publish the observations in a scientific journal. “I’ve seen one at a carcass, but I assumed it was just gnawing on the bones, as I've found numerous bones and antlers with gnaw marks from hares and from rodents. Maybe it was actually eating the meat too?”
One of the strangest discoveries among the recent data, says Peers, is that hares eat the feathers from the carcasses of a bird called the spruce grouse. It’s unknown how their stomachs are able to digest these feathers, which may be a source of fiber. (Read about how snowshoe hares are coping with climate change.)
“It’s known a lot of animals we assume are herbivores do actually consume meat,” he says. “The reason this is a new discovery is the scavenging of the feathers. A lot of ecologists were surprised at that."
Intentional ingestion of feathers—which are mostly made of keratin and contain little protein—is extremely uncommon among mammals, he says.
He was also surprised to find the hares would defend their carcasses from other hares. Peers thinks the reason hares weren’t found on larger carcasses—say an elk—is because of competition. Being so small, they don’t have much chance to feed on a kill that has bears or wolverines on it. But something similar size, like another hare, is perfect.
Many other studies in North America have blurred the line between herbivore and carnivore.
Cottontail rabbits have been seen scavenging grouse in the Appalachians, cows prey on bird eggs and chicks in Wisconsin, beavers eat dead salmon in Alaska, and white-tailed deer in the Dakotas raid ground-dwelling birds’ nests.
Other cold-dwelling vegetarians, like Arctic ground squirrels, have been seen hunting lemmings, says Rudy Boonstra, an ecophysiologist at the University of Toronto Scarborough who discovered this similarly striking behavior in the late 1980s. (Read about prairie dogs that murder their competition.)
“It’s quite remarkable,” says Boonstra, a co-author on the new study. “These herbivores are not true herbivores."
While studying lemmings in the Northwest Territories, Boonstra observed squirrels hunting lemmings, digging them out of burrows and bringing them to their own dens to consume them.
“The first thing they would do is eat the brains,” he laughs. "In winter, most of these herbivores are on a protein-deficient diet, and they’re trying to make up for it.”
Boonstra adds the Arctic ground squirrel behavior poses a compelling question: Do snowshoe hares ever seek out and kill small prey?
There’s no evidence of this, at least not yet, and Peers says he plans to continue his research. But if the past is any guide, the snowshoe hare menu may be more paleo than we ever imagined.
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