Zoology

How Mammals Hibernate



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"How Mammals Hibernate"
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Mammals are the only animals that we are aware of that hibernate and not all do.

True hibernation may be best displayed by the woodchuck. The woodchuck is a type of marmot. They live mainly in North America. Woodchucks prepare their burrows for the coming winter. They don't line it with food, but make sure it is deep enough to avoid the extreme elements. They also have a water source.

These animals strive to have large stores of fat so their body has something to use to keep the animal alive during winter. Essentially the summer and fall are spent getting fat and happy for winter. They need to have enough fat reserves for warmth and energy. True hibernators don't actually sleep all winter. About every two weeks they wake up to drink and defecate. They also need to move about some so their muscles don't atrophy. It can take from twenty minutes up to several hours for them to wake fully.

The body temperature of true hibernators are very low. It usually stays around 40 degrees Fahrenheit. Their heart rate slows down from about 100 beats per minute to four beats per minute. Their breathing slows to one breath every three to four minutes. You can see why it would take so long for the body to wake up and perform tasks at a normal rate. There are very few true hibernators.

Bears have a very unique form of hibernation, it is really dormancy. Bears can wake up quickly and react in an emergency. They have also somehow adapted so they don't need to drink or eliminate waste during the entire hibernation time. They can "hold it" for up to seven months. Their muscles do not show the signs of atrophy from being so still either. They are truly unique.

Then there are a myriad of other mammals that show another form of dormancy. They display more of a winter lethargy. These would be raccoons, opossums and skunks to name a few. They simply sleep through the harshest part of the winter, living on their body fat. They den together to count on each others heat for body warmth. They display little or no changes to breathing rates and body temperatures.

No matter what type of hibernation these mammals display there are two essentials to prepare. These are shelter and food. Food can be in the source of stored fat or actual stored food. These must be taken care of or they simply don't survive the winter. As fall approaches all focus is put into building stores of body fat. Instinctively they have learned what types of food are best.

The burrow or den usually is made very quickly in one or two days. They don't look very comfortable to us, but they must do the trick!

It sounds a little comforting doesn't it? Just shutting down for a few months and resting.

Reference:
www.chattanooganaturecenter.org
www.enchantedlearning.com

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