Season to hibernate

At this time of year, everyone seems to be thinking about staying indoors, eating good food and watching a movie. This would be the human version of hibernation. But actual hibernation is much different.

The act of hibernation only occurs in warm-blooded animals. Yes, it is true, humans are warm-blooded animals, we still don’t hibernate like other mammals. Hibernation is best described as a period of time (usually winter) where the entire metabolic system of the animal is suppressed. Its physical characteristics are shown by lowering the body core temperature, slowing the metabolism, decreasing respiration, and lowering the heart rate. It is important to understand none of these things actually stop. They just slow way down. The overall effect is to conserve the warm-blooded mammal’s stored fat (energy) so it will last the entire period of hibernation.      

The key to any successful hibernator is the amount of body fat it has stored upon starting hibernation. The fat is the fuel that will sustain them all winter. If the animal doesn’t have enough fat, it will simply run out of fuel before spring and will die. Accumulating this fat during fall is extremely important, requiring that most hibernating animals constantly feed during every waking hour of the day. Some animals, such as bears, will eat for 20 hours a day. This is called hyperphagia. 

All mammals (which include humans) maintain a constant body core temperature, usually in the high 90s degrees F. Even a slight deviation of just a couple degrees, either higher or lower, dramatically affects the animal. Think about yourself for example. On average, you have a body core temperature of 98.6˚ F. With just a two degree rise in temperature, you will be running a low grade fever. A rise of four degrees and you are burning up with a high grade fever, and you will be very ill. Conversely, if your temperature dropped four or five degrees you would be hypo-thermic, and you would be nearly unconscious from the cold. Now consider that a bear may drop their body core temperature ten or more degrees, and you can start to see how amazing hibernation can be.

Looking at respiration, we breathe about 10-12 times a minute. During hibernation, respirations drop to only one or two times a minute. A heart rate that runs about 100 beats per minute in many animals drops to 20 or 30 beats thus slowing the flow of blood to the entire body, including the vital organs such as the liver, kidneys and brain.

Some mammals that are considered true hibernators include many species of bat. Some bats will migrate to warmer climates during winter, while others move into caves where they will hibernate. In fact, bats will be so cold during hibernation that they are covered with a layer of frost. In northern states, hibernating bats may be in the cave for six or seven months.

Woodchucks are also a true hibernators. These plump, short-legged critters feed non-stop during fall and enter their winter den with a layer of fat so thick they look like furry pigs, hence their other common name, whistle-pig. Once a woodchuck enters hibernation, it is down for the entire winter.

Everyone knows about bears hibernating. But, actually, bears are not true hibernators. Yes, when a bear is hibernating, its heart rate, respiration, and all other bodily functions are greatly reduced, but the bear is still awake. Amazingly, female bears give birth to young during hibernation, remaining awake to care for their young.

The Eastern Chipmunk is also not a true hibernator. It gathers food in the fall and stores seeds in an underground burrow. During winter, the chipmunk will periodically wake up to eat, to build up their fat reserves before going back into sleep.

Other critters, such as raccoons and skunks, don’t hibernate at all, but rather just take a break during the coldest parts of the winter. They will hold-up in a den and just sleep for up to six weeks. So, if you are like me and you feel like hibernating, remember the first thing to do is put on a nice layer of fat. Until next time…

Stan Tekiela is an Author / Naturalist and wildlife photographer who travels the U.S. to study and capture images of wildlife. He can be followed on and He can be contacted via his web page at


The Drummer and The Wright County Journal Press

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