Email this article Discuss this article

Tiem to hibernate?

Few species actually do it for the winter

Mike W. Bryant
Northern News Services

Yellowknife (Oct 05/01) - As Yellowknifers prepare for winter, it would perhaps seem natural that the animal kingdom would follow suit.

Not so, says Dean Cluff, a wildlife biologist with the Department of Resources, Wildlife and Economic Development.

NNSL Photo

The arctic ground squirrel, like its more southerly cousins, is one of few "deep" hibernators found in the North. - photo courtesy of Dean Cluff

Technically, only a handful of species in the North Slave region hibernates.

Wood frogs, ground squirrels, black bears and the few grizzly bears that venture south of the tree line all call it a year come wintertime around here.

But ground squirrels, which are uncommon in this region, are the only deep hibernators among them.

Deep hibernators dramatically reduce their body temperature, heart and metabolic rates, dropping them down to next to nothing when they den. Black and grizzly bears experience only more moderate hibernation, what biologists call "torpor."

"It allows them to arouse easily," says Cluff.

In torpor, a bear's body temperature will drop 7 or 8 degrees and its heart rate will decrease to about 40 beats per minute. While they arouse more easily, they don't leave their dens as often.

"Deep hibernators go through periodic arousals, maybe once a week," says Cluff. "They feed, they defecate and urinate, and then they enter hibernation again."

Bears, says Cluff, are more sophisticated hibernators be-cause they recycle body wastes, and do not have to rouse to expel them.

Most animals that live around and near Yellowknife during winter, including ravens and ptarmigans, are active year-round. "One strategy is to grin and bear it," says Cluff. "A climate can be harsh, but if it's predictable you can adapt to it."

Mammals like voles, mice and shrews spend winter scurrying under the snow, their tiny bodies and high metabolism preventing them from entering hibernation.

That means short-tailed weasels, pine martens and mink have access to food all winter and do not need to hibernate.

Red squirrels, meanwhile, keep a food stash and larger game like caribou and moose root through the snow for vegetation to eat.

Whether hibernating or sticking it out, winter is a challenging time for animals.

Naturalist and writer Jamie Bastedo recently finished writing a novel exploring a grizzly bear's take on hibernation.

Tracking Triple Seven, says Bastedo, "tries to describe what it feels like waking up after months and months spent hibernating.

"They can spend seven months in their dens on the Barrens."