WINTER WORLD

The book is mainly about adaptability. It explains how birds, mammals, amphibians and insects are able to survive and even thrive in relentlessly cold and snow-covered lands. The chipmunk above, for example, builds a 12-foot burrow system that includes a nest chamber three feet underground, several food storage chambers, and escape tunnels as well as the main channel. They hibernate, not when it’s cold, necessarily, but when there’s a low food supply.

Hibernating mammals like the arctic squirrel awaken and warm themselves up to their usual 37† body temperature periodically during the winter, for no apparent reason except to get REM sleep.

My friend the beaver, creator of the fine work next door to us (a bog), builds a conical lodge that looks much like a tepee and functions similarly. Up to ten feet high, in three feet of water, it freezes solid in winter, protecting the beavers from the elements and predators, with a small air vent at the top. Entrance is only from under the ice, which is why beavers cut trees and drag them to the pond so they are accessible from under the ice all winter long (beavers don’t hibernate, and eat up to 50lbs of wood per day each).

Wren males build the nest framework, and in some cases build multiple nest frameworks. Then the females choose their mates, and do the interior lining and finishing on one selected nest, to seal the marriage.

The book is an engaging read with some amazing stories. At its heart it is also a mystery. There are many methods that Northern animals use to conserve energy, and science is able to show how in combination they allow so many species to live comfortable lives in what we would consider inhospitable surroundings. Heinrich’s mystery is the golden-crowned kinglet, a tiny (not much more than 1″ long with feathers, weighing 4-6 grams), energetic bird that is seen periodically in small groups in Northern winters. These birds defy Heinrich’s scientific explanations and investigations — with such tiny weight and size and such huge energy use they should simply not be able to survive in cold climates. The mystery remains unsolved — at least until Heinrich’s next book.