February 2

North Cairn: Creature comforts sparse in winter

It’s an annual survival test for animals.

I keep thinking about how the animals are faring.

The dog and I are well into the half-cord of wood stacked under the lean-to out back of the cabin, cultivating a ritual of toting timber into the house any time we venture out, keeping the loads light but more or less constant.

As a result we are finding that one of the big winter challenges is learning how to run a wood stove and kerosene heater efficiently but without blasting us outside to flee overheating, an odd occupation during these cold days and arctic nights that everyone – human or animal – must accommodate to survive.

Everything is uneven, unbalanced as usual, in our eccentric little dwelling in the woods. Upstairs, it is cold – perfect for sleep; downstairs so warm the dog has taken to sleeping on the tile floor by the back door, where there is always a horizontal line of cool air wafting in at nostril level for her.

Her struggle to reach temperature equilibrium always keeps the fate of wild animals at the back of my mind, ready to drift forward like a slow-moving herd of yarding deer. The herculean labor of survival in the wild is hard to ignore when just going for a short walk makes one feel, as a friend said last week, “like my eyes are frozen.”

We take it for granted that the plants and birds, amphibians and mammals, will make it through just fine. (The mice and ticks, we know well, will inherit the earth.) But for all creatures, these extremes of weather – in Maine and across the country – are a very real challenge.

I think of all the skills animals have refined through adaptation and evolution, but this weather almost seems to supersede those powerful dictates. Even so, most creatures rely on tried and true methods to react to the extreme cold.

Birds shiver, for example, producing heat five times their normal rate. Many small mammals will hunker down in a protected spot – the crook of a branch, a hollowed out trunk, an underground lair or in the walls of a home – and stay there until the worst weather passes or they have to go out in search of food.

Most wild animals native to Maine tend to be fairly well-suited to persevere through the sub-zero wind chill or the mountains of snow, wildlife specialists around the state confirm.

Periods of extreme weather come and go, so a native species that persists over time develops survival strategies that cover those contingencies, Sarah Cunningham, assistant professor of captive wildlife care and education at Unity College, explains.

The methods may include full hibernation or some variation on the theme. Many mammals, too, are able to shake off a snooze when conditions demand. That includes bears, often mistakenly thought to be full-time, all-winter hibernators. Other occasional hibernators include opossums, raccoons, skunks and squirrels.

The strategy nature has bestowed on black-capped chickadees is to lower their body temperatures 10 to 12 degrees and slow their metabolism at night. Eventually they slip into an unconscious state – torpor – to protect themselves.

Circulation of bearable temperature occurs through a system of vessels that brings warm blood in the arteries alongside veins carrying cold blood back to the heart. The combination serves as a sort of radiator and ensures that the bird’s feet don’t freeze.

Some birds – including chickadees and goldfinches – add extra feathers during summer, as much as doubling the number, to prepare for the dead of winter. On a very cold night, these birds puff up their feathers to create a layer of downy insulation that can reduce heat loss by as much as 30 percent, ornithologists have learned.

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