“Perhaps I am a bear or some hibernating animal underneath, for the instinct to be half-asleep all winter is so strong in me.”  – Anne Morrow Lindbergh

So true. When it is dark and cold outside, in late November, December and January, all I want to do is put on warm sweaters and cozy up to a roaring fire in the fireplace. Add something that warms my insides as well and I’m happy, and half asleep.

True hibernation is an amazing thing – and is characteristic only to mammals like us. In years past, scientists believed that when hibernation occured, the only change was that body temperatures dropped. Then scientists discovered that in addition to the drop in body temperature, metabolic changes occur. Animals that truly hibernate do so for extended periods of time without needing to eat, drink, or eliminate body wastes.

Bears are the species we most commonly think of when we talk of hibernation. Black bears, and their cousins, brown (grizzly) bears, hibernate for at least three months. During their hibernation, bears may lose 15 to 30 percent of their body weight. Although the body temperature drops some, it is minimal. Heart rate and metabolism slow dramatically. 

Another thing about bears, they usually mate in summer. It only takes a bear embryo about a month to fully develop. However, female bears delay implanting the embryo until late winter, so that the cub’s birth will occur about the time they are ready to leave their winter den. Food and the weather conditions will have improved by then, increasing the odds of the cub’s survival. 

Other hibernators include several members of the rodent family. Chipmunks hibernate. They lower their body temperature to near freezing but instead of sleeping for extended periods, they wake up every few days. This raises their body temperature close to normal. They eat food they have stored, and eliminate body wastes. Then they lower body temperature and ‘hibernate’ for several more days. The cycle is repeated.

Bats also hibernate. Do you know of any other mammal species that disappear into their dens in the winter and don’t come out until spring? Tell us about it – or send me a comment and I’ll investigate and share what I’ve discovered in a future post.

Meanwhile, if you’re hibernating, it may just about be time to wake up! Spring is coming!