Why do bears hibernate?
(Lansing State Journal, February 19, 1998)


     When fall turns to winter and the temperature dips, the food sources for the wild animals becomes very scarce.  Some animals wait out the harsh conditions of winter, constantly searching for food and shelter.  Other animals, like the bear, spend the winter in hibernation.

     Hibernation is a dormant sleep-like state.  By going into hibernation the bears bypass winter when their food supply, nuts and berries, disappears.  Animals like the bear would find it extremely difficult to find enough food during winter, and therefore go into hibernation.

     During hibernation the bear cuddles up in a cave or in a hollowed out tree, safe from the dangers of winter.  In order to survive this long period of inactivity the bear must build up its body weight by accumulating fat.  In the months before  hibernation bears can gain up to forty pounds of fat per week.   A bearís body goes through several changes once it enters hibernation.  Its heartbeat drops from fifty-five beats per minute to ten beats per minute, and the bearís body temperature will drop from five to nine degrees below normal.  While in hibernation the bear uses  the stored energy it accumulated as fat to survive.  So a bear can lose from fifteen to forty percent of its body weight during the winter just by sleeping!

     Bears will generally enter hibernation in early October and emerge sometime in April or May, when their food is plentiful again.  The hibernation cycle is just another unique adaptation of nature that allows many animals like the bear to survive during the severe conditions of winter time.


[ Back to Ask Science Theatre | Back to Ask Science Theatre Date Index ]
Back to MSU Science Theatre Home Page