When I think of an animal that hibernates my thoughts turn automatically to "bear." Bears find a place to spend the winter and then hibernate. My world as I knew it changed the other day when I came across something in a book that says bears do not actually hibernate. When I told a friend this he asked, "What do they do then?" Of course I couldn’t remember so I did some more research and found this from a website.
A common misconception is that bears hibernate. While it is true that bears are inactive for much of the winter, they are not true hibernators. Although they sleep for weeks at a time, their body temperature only drops 10 to 15 degrees, and they can wake up very quickly, as any researcher working with bears will tell you. They also bear their young during this time, an activity that requires them to produce milk — a process impossible in true hibernation. Other of our winter residents such as raccoons, fishers and deer mice sleep for varying periods of time through the worst weather when foraging for food is all but impossible.
I found many references to bears hibernating including one on this website.
Once considered not true hibernators because of their high body temperatures in winter, black bears are now known to be highly efficient hibernators. They sleep for months without eating, drinking, urinating, or defecating. Hibernators with lower body temperatures, such as chipmunks, woodchucks, and ground squirrels, cannot do this. These other mammals must awaken every few days, raise their temperatures to over 94°F, move around in their burrows, and urinate.
So in spite of the few articles that are contrary to my popular belief I will still say, "Bears hibernate." A bear spends all summer eating to prepare for a long winter’s sleep. The bear must consume large amounts of food so it can survive the winter cold without eating. The bear’s coat will get thicker for heat conservation and brown fat will develop around it’s heart, lungs, and brains. The metabolic rate will be cut in half allowing the bear to live off of it’s fat stores for the winter.
Black bears also greatly reduce their kidney function in winter. They do not urinate for months but still do not poison their bodies with waste products such as urea. The urea is somehow broken down and the nitrogen from it is reused to build protein. This ability to build protein while fasting allows the bears to maintain their muscle and organ tissue throughout the winter.(website)
In reading about bear hibernation I came across an unfamiliar word, "torpor." This was the word used to describe the state of an animal that wasn’t really hibernating. A definition I found on the web said, "The dormant, inactive state of a hibernating or estivating animal." I personally think the hibernation/torpor debate is something for scientists to talk about in the lunchroom.
Whether or not a bear is in a state of hibernation or torpor it doesn’t really matter. A bear accomplishes a great feat every year when it can go up to 7 months without food, water, or going to the bathroom. It seems logical to me to believe an animal that sleeps throughout the entire winter and doesn’t have to get up to go pee is doing something right, hibernation or torpor, I’m impressed.