Winter is nearly here. For some creatures it's time to hibernate. Hibernation is a way of conserving energy during the cold winter months and surviving when food becomes scarce. It is not difficult to think of a few creatures that hibernate over the winter. Probably, the first one that comes to mind is the bear. But are all hibernators equal? Let's see.
First, consider the "true hibernator". True
hibernation means going into a dormant or inactive state. Normal body functions (metabolism) slow down. The heart beats less often. Body temperature decreases. Movement becomes less frequent. There is little response to external stimuli. They must wake, move around, eat and defecate every few days. The creature may appear dead. It lives on stored energy reserves or fat. True hibernators are able to reduce their body temperature to near freezing - a level that would be fatal under ordinary conditions. They are able to generate heat in order to revive themselves. What animals are true hibernators? Mainly bats and rodents such as ground squirrels, marmots, woodchucks, dormice, hamsters and hedgehogs. For example, the
woodchuck is able to lower its heartbeat from 80 beats per minute to about 4 or 5 beats a minute and body temperature from 98° F to 38° F during hibernation.
Bears have been classified as true hibernators, deep sleepers or false hibernators. One researcher considers bears super-hibernators or highly efficient hibernators, sleeping for months without eating, drinking, urinating, or defecating. The hibernating bear's body temperature stays within 12° of its active summer temperature, allowing it to react quickly to any danger. Any waste products produced during hibernation are recycled.
There are other types of dormancy. Some animals, such as skunks, bats, frogs, poorwill and raccoons, go into something called torpor - a time when their heartbeat, temperature and activity decrease. Torpor is not as deep as hibernation and usually does not last as long. A creature can go into torpor for just part of a day - diurnal torpor. Some call winter torpor - hibernation and summer torpor - estivation. Insects experience a type of dormancy called diapause - a time when they do not grow and their body functions slow down. Insects, which experience diapause, include the gypsy moth, grasshoppers and some butterflies and moths.
