When winter closes in over most of the country, man heads for the islands (opposite) or buys himself a new overcoat. Animals make less fuss about coping with the cold. Some grow winter overcoats, others shut out the frigid and uninviting world by hibernating.
True hibernation is an astonishing process. By this comfortable device an active, warm-blooded animal, which is usually busy converting food into energy, suddenly chucks the whole business. Biologically speaking, the critter shuts up shop. Its metabolism slows way down. Its body temperature drops to within a few degrees of its surrounding temperature. Breathing and pulse are barely perceptible. The animal enters a nether state bordering on death. In this condition it loses hardly any weight as it remains in its den and lets winter go hang.
According to this definition the black bear, although widely considered a hibernator, doesn't really hibernate at all. When the bear goes into its den or curls up in a deep snowdrift it goes to sleep or languishes in a state of drowsiness. Its body temperature remains normal; it is using up its fat and it loses weight. It may be asleep but it is very much of this world.
FEMALES GIVE BIRTH
Many a hunter has stumbled onto the winter den of a bear to find that the occupant was far from insensible. Dr. Harold E. Anthony, chairman of the Department of Mammals at the American Museum of Natural History, gives further proof that bears don't hibernate in the strict sense. If a female bear was really in the comatose state of actual hibernation, he says, she would be unable to give birth to her young in winter and nurse them.
The largest of the true hibernators in this country (with the exception of the hoary marmot, a somewhat heftier, very close relative who lives in the Northwest and whistles) is the well-known woodchuck. When the weather gets cold and food is scarce, it just crawls into its burrow and rolls itself up into a tight ball with its head between its legs. Its breathing becomes slower and slower until a mere trickle of air enters its lungs. Its pulse weakens and its body grows colder until its temperature is down around 45 to 55°.
Once in this state the woodchuck has knocked himself out completely. Yell at him and he shows no sign of hearing. Touch him and he makes no response. Lift up this inanimate ball of fur and carry it into a warm room and you'll find that, unlike the bear, the woodchuck is not easily aroused. He takes his time. Sometimes it takes several hours for him to become his normal, alert self. The first sign that he is on the road back is a gradual increase in the rate of his breathing. He uncurls a bit and his eyelids flicker. His paws make little movements as though he were having a dream.
When his breathing has reached a normal rate he gasps as his sluggish lungs get to work again. In time he tries to get to his feet. He is recovering now and shivers miserably. At last he is ready to resume normal life—the woodchuck who came back.
There are many hibernating mammals but some of the more familiar ones lack this facility. First-class hibernators include ground squirrels, chipmunks, some bats, prairie dogs and jumping mice. Skunks crawl into a hole and drowse for several weeks but they don't hibernate. Neither are raccoons true hibernators, although they too can sleep away a cold spell.
At various times it has been suggested that it might be good for people to try hibernation, that it might be good for a man to relax for a while. About the only instance I know of a human being attempting hibernation was in the case of the late Arthur E. (Turkey) Gehrke, the hibernating barkeeper of Watertown, Wis. At the first cold spell of November Gehrke, a 230-pounder, would crawl into his bunk and remain in his locked bedroom on the second floor until spring. But Gehrke was like the bear: a sleeper but not a real hibernator. His wife had to sneak food up to him on a dumb-waiter.