Most mammals with which we are familiar, such as weasels, fox, muskrats and rabbits, are usually active all winter long. Some will actually face the severe hardships squarely, hunt their food daily - except through the severest weather - and usually do not attempt to store food supplies.
The small field mouse and Red Squirrel, on the other hand, will store food supplies in what are called caches for consumption at a later time. Similar in behavior to birds, mammals survive by large consumption of food and abundant internal heat production. Hibernation is another means of survival for this group of animals. We are familiar with the bear and woodchuck, as well as the countless stories of these two animals and the interesting tales of unfortunate humans who accidentally cause the bear to arise during a winter sleep situation. The woodchuck, a milder creature, responds to this type of arousal with a more subdued behavior.
Several members of this family respond to the changing seasons by migration treks to more subdued habitats. The tales of the Elk migrations in Yellowstone Park, Wyo., are a classic example of a mammal response to adverse weather conditions. While I have had an opportunity to visit that site and observe the Wyoming Elk feed, I did not observe this particular migratory behavior.
Typical mammals of the area include a woodchuck
and below far right, the fox squirrel.
and raccoon nest.
Bob Peterson photographed above, the elk
Probably the most familiar winter behavior that most of us have heard about is hibernation. Scientists have begun to determine that many of the animals we presume to be hibernators are actually in a state of winter sleep, or dormancy, and can be aroused if disturbed. Biologically, scientists who have researched the process of hibernation are still under the impression that more research is needed to fully understand this event. Some other hibernating or winter sleep mammals in our area include bats and the popular chipmunk.
I always enjoy observing the behavior of the many small mammals that feed upon the seeds knocked to the ground from my bird feeders. Also, the behavior of squirrels and chipmunks as they search for a method of reaching the direct source of food on the feeder. Watching a little squirrel or chipmunk jump several feet with amazing success from an awkward perch on a tree or house roof to a small feeder is admirable in the survival of these small animals.
The causes of hibernation have been studied for several years and current theories are being proposed. The definition of "hibernation" and the prior use of the term "winter sleep" are both being associated with the fall of the temperature of the atmosphere as well as the decrease of normal atmospheric pressure, which causes the slowing down and weakening of respiration in many of the affected animals. This process appears to slow the circulation of blood, creating drowsiness in the animals affected.
The hibernating woodchuck is one of many mammals studied over the years to determine the cause of hibernation. It was thought, very early on, that the process of hibernation may have been influenced by periods of cold, hunger, darkness and quiet, which may have influenced this behavior. However, this reasoning has been questioned over the years. Temperature, both warm and cold, still seems to be the best reasons for winter hibernation and summer sleep (aestivation) recognized by scientists.
While we have discussed the woodchucks with the process of hibernation, the same cannot be said for the fox or raccoon, which are known winter sleepers, and not hibernators. This means that they can be aroused very easily by external conditions during this period.
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