Wild Things: How to keep warm

A black-capped chickadee. Ed Kanze Photos

A red squirrel.

By ED KANZE

Keeping warm in winter poses challenges for wild things, the warm-blooded ones that don’t migrate or hibernate. To live without the benefits of central heat, hot meals, hot drinks and L.L. Bean, animals must improvise. How? A quick look around the yard or the neighborhood will answer the question.

Birds do it with feathers. They have contour feathers for keeping out the elements, primary feathers for getting off the ground, and, in this simplified summary of bird plumages, down feathers for holding in heat. Bird feathers can be elevated as needed by muscles under the skin. This gives feathers greater loft, which increases their ability to insulate. Mammals do something similar. Unfortunately, our recent ancestors gave up most of their hair, so when we try to erect our fur, all we get is goosebumps.

Thickening insulation cuts down on heat loss, but there are other ways to do it. Songbirds such as the black-capped chickadee roost at night in snug places, often near trunks under evergreen boughs. There they tuck in out of the wind, slashing the wind chill factor. Some birds take this a step further and go indoors. Woodpeckers may retreat to hollows they excavate in trees, or in birdhouses, and songbirds may squeeze into such places, too.

Insulating and hiding are just the start. Birds also cut down on activity during the coldest weather. The fewer calories a bird expends moving around, the more it has to keep its inner fires burning. Speaking of calories, this brings up one last stratagem: increasing food intake. Finding extra food can be hard to do in winter, but when nature provides, birds consume with gusto. If you maintain a bird feeder at your house, you are reminded of this every time you buy another bag of seed.

Mammals? We do it with hair — hair that in wild animals in cold climates tends to become thicker in winter. Summer coats are shed, to be replaced by winter pelage in which hairs are packed closely together. Some or all of the pigment inside each shaft of hair may be sacrificed in order to make room for air. Hollow, air-filled hairs provide better insulation in winter than the fine, pigment-rich hairs of summer.

Reduction of activity, similar to that in birds, helps wild mammals make it through cold winter days and nights. When the weather turns extremely cold, we see fewer and fewer tracks in the snow. That’s because the animals aren’t moving, or they’re moving less. In the bitter heart of winter, raccoons may hole up in hollow trees, sheds, or attics and sleep for weeks without rousing. Same for skunks. Same for all sorts of creatures.

When I offer nature programs in winter, I often bring along skins and skulls for show-and-tell. Typically I show an otter pelt and the furry skin of a beaver. My wife and kids bought the skins for me from a catalog. Most days, the sight of the skins provokes thoughtful discussion about human options for keeping warm, and how we feel about them.

Lacking thick fur coats of our own, we must wear fur, knit, weave and sew or go shopping. Most of us go shopping. What do we buy? Most people these days, I find, are horrified at the idea of fur coats. I confess I’m not terribly keen on them myself. But what are the alternatives? We can, as I often do, wear a bulky wool coat, but wool comes mostly from sheep, and the raising of sheep is far from environmentally friendly. Down? We don’t have to think too hard to conjure down’s downsides. About all that’s left is synthetics. I often arrive at a program wearing a jacket insulated with synthetic fiber and sheathed in nylon. That stuff comes from petrochemicals. Environmentally pure? Not by a country mile. Nothing is. So we’re left to pick our poison, so to speak, in order to stay alive.