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As the first snow blankets the land, most of us retreat inside, spending much less time outdoors compared to the previous six months. We have learned in the north to cope with the cold, and the wet and soggy conditions on the respective coasts, by building homes and workplaces that are warm and weather proofed. So how does the rest of the animal kingdom in our province contend with winter?

There are three basic strategies for surviving winter’s rigors: migration, hibernation and resistance. From an evolutionary stance, they amount to choices between avoidance and confrontation. Animals either leave the frozen landscape for warmer and more hospitable lands to the south or, with remarkable stamina and adaptations, they stick around.

At first glance, migration appears to be a safe alternative. It is for some, but like all choices, there are consequences. A 600-mile flight costs birds 50 percent of their total body weight as fat. And adding more weight for flight has practical limitations.

In addition, waterfowl have added stresses imposed by humans as hunters gather along migratory routes. A Canada goose that leaves Atlin, British Columbia in early September and arrives near the Salton Sea in southern California may face three months of being a target for shooters. The goose season opens progressively later southward along the route. 

Some birds, like herons, are specialists and they cannot change when environmental conditions change. The slightest cover of ice prevents the heron from making its living: fishing. Others, like fly catchers, need insects and when it gets cold their food source metamorphosizes, so they must fly south. Many birds have no other choice but to migrate.

It would cost a mammal of the same weight about 10 times more energy moving over a given distance by running compared to a flying. In nature, there are always exceptions. The caribou move hundreds of miles between summer breeding grounds in tundra and winter boreal forests of northeast British Columbia. Marine mammals, like blue whales, migrate vast distances as swimming appears to be even more energetically cost efficient than flying.

Hibernation is a viable alternative to migration for some. Hibernating mammals posses a unique ability to lower both their metabolism and body temperature. They cannot, however, drop below 32 degrees Fahrenheit. If they near the freezing mark then they awaken, restore body temperature to its normal state before re-entering hibernation. That costs a large amount of their fat reserves and could jeopardize their chance of surviving the winter.

Cold blooded animals like reptiles and amphibians cannot control their body temperatures so hibernation is their only means of survival. Most seek out safe winter hiding places usually under decaying logs, deep protected rock crevices or in the burrows of other animals where they can escape subfreezing temperatures. For instance, rattlesnakes in the Kamloops, British Columbia region congregate in rock dens or the 50,000 red-sided garter snakes at Narcisse Snake Pits Wilderness Park in Manitoba.

Some frogs tolerate ice formation in the space between their cells and protect their living cells with a sweat alcohol called glycerol. Others, supercool their bodies so that they can tolerate temperatures of about minus 23 degrees Fahrenheit. If the temperatures drop below this critical point the frog will snap-freeze all at once and die. 

For many organisms that do not migrate or hibernate there only strategy is to resist the cold. Over-wintering insects and tree buds for example do not generate any appreciable heat so they must depend upon complex biochemical mechanisms to protect them from freezing temperatures. Mountain pine bark beetles produce glycerol which prevents ice formation in their body tissues, permitting them to cool without freezing to minus 40 degrees Fahrenheit.

Many animals are well adapted to contend with snow. Spruce grouse grow extra scales on their feet enabling them to grip the snow while feeding on icy branches. Caribou, with feet seemly way out of proportion to their body size, float over snow as if walking on snow-shoes. Lnyx, too, have huge snow-shoe-like paws which enable them to walk on snow without sinking. And the musculature of the moose legs enable them to move through four feet of snow with ease.

All of the organisms that live in northern North America are miraculously adapted to cope with winter. Those that are not must migrate to warmer environs. Each strategy has its advantages and dangers.


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Dr Reese Halter is a public speaker, conservation biologist, and founder of the international conservation institute Global Forest Science. His most recent book is The Incomparable Honeybee and the Economics of Pollination  Contact him through



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