Why do bears hibernate?

(Lansing State Journal, Feb. 2, 1994)

Question submitted by Norm Nethaway.

According to the scientific definitions, what bears actually do resembles more of a deep sleep.

We say that an animal is hibernating when it goes to sleep where its metabolism and body temperature are reduced significantly during the winter months. A bear goes into a deep sleep during the cold days of winter but does not reduce its metabolism as much as a true hibernator.

The woodchuck, the thirteen-lined ground squirrel and the meadow jumping mouse are the three mammals in Michigan that are true hibernators.

As you may know, winter is cold and harsh. It is the toughest time of the year for animals to survive.

Mammals, such as bears, must stay warm to survive. Thick fur helps, but bears still need food energy to maintain their body temperature. This is a real problem as food is scarce during the winter. With less to eat, bears and other animals have less chance to acquire enough food to stay warm and move around. Animals use less energy when they sleep than when they are active. So bears conserve energy by sleeping. Even though they are inactive, bears have to build up a store of energy to make it through until spring. This store of energy takes the form of thick layers of fat, built up over the course of the previous season. As winter approaches, bears, all fattened up by several months of good eating, find a cozy den to snooze through the coldest months of the year. When spring comes around, they wake up hungry and go out to find their first good meal of the year.

David Belanger contributed to this article

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