Roxanne Roy, age 13, of St. Paul, Minn., for her question:
How can bears hibernate without food?
In wintry climates only a few of the wild animals are around at Christmas time. Most of the birds have migrated southward. Reptiles, amphibians, certain bats and mammals are hibernating. The sleepy bears are almost, but not quite, hibernating.
True, hibernation is somewhat like a coma and much deeper than ordinary sleep. A hibernating woodchuck will not stir if you lift or move him. He remains asleep even while you take his temperature and check his pulse. This medical check up reveals that his pulse and heartbeat are very slow and that his temperature is way below normal. The sleeping woodchuck is an example of true hibernation.
The bears although he sleeps soundly through the winter months.is not a true hibernater. His temperature and heartbeat are only slightly below normal and disturbances arouse him. If the cold, wet snow drifts into his den, he wakes up and sets forth to seek a more dependable shelter. If you went into his winter hide away and poked him, chances are he would wake up and give a disgruntled growl or even swipe at you.
Both the woodchuck and the bear eat extra food during the late fall, and neither eats nor drinks during the winter. Their body processes, of course, need food through the long sleeping period. But the feasting of the fall season provides extra layers of fat. During the hibernation of the woodchuck and the partial hibernation of the bear this excess fat is gradually burned to keep the body processes going.
The woodchuck can fast longer than the bear because the processes of breathing and heartbeat are slowed down during hibernation. The bear uses more stored fat because his body processes are almost as busy as when he is awake and active. Bruin is a plump fellow when he beds down for the winter. But as his fat is used up he becomes thinner and thinner, and spring finds him thin and scrawny.
He does not, however, seem to feel ravenously hungry. He nibbles a few tender shoots and saunters around to find a sip of clear water and does not devour a large meal for some time. After all, his stomach has been idle all fainter and needs a while to get used to food again.
The winter sleep of Mrs. Bruin is more interesting. Her babies are born in the middle of the winter. For the first few weeks of life their whole world is a cozy den. They care nothing for the blizzards raging outdoors, for indoors they have a huge furry mama bear to cuddle and warm them and supply them with mothers milk.