Winter brings on many changes in animals lives, whether it be migration by animals such as the whales, seals, turtles, eels, crabs, fish, butterflies etc.
However, for some animals hibernation is the preferred method of escaping the cold of winter.
For example, the small ground squirrel illustrates some of the remarkable changes that take place. It’s body temperature drops to within a few degrees of the cold outside its den. The heart will beat only once or twice a minute. When it is active, the squirrel may breathe a few hundred times each minute, but in hibernation it takes a slow breath only once every five minutes. Despite these changes, its blood remains saturated with oxygen, and little used muscles remain in tone ready for action when they awaken. Bears however, are not true hibernators. The body temperature of bears stays normal. They burn an estimated 4,000 food calories a day. While in hibernation they can awake and move about quite often. Yet they can exist for three months or more without food or water.
During their hibernation, the bears neither defecate or urinate. This would normally mean that nitrogenous wastes during that time would cause poisoning to the urinal system. However this it does not do. The bear solves its nitrogenous waste problem by a form of recycling." The hibernating bears body diverts nitrogen from pathways that synthesise urea into pathways that generate amino acids and new proteins. And it does this by glycerol (produced when fats are metabolized) and recycled nitrogen as the building blocks" according to the New Scientist Magazine of February 1985.
The female grizzly bear will have her cubs during the winter hibernation. During hibernation she does not eat or drink anything at all, yet still she is able to nurse and care for her cubs. The mating period usually occurs in may to early July each year, and the cubs are born generally around January or February, right during the cold winter months. But the gestation period is not very long for the female. She has very tiny offspring usually weighing only a pound or two at birth, so it is easier for her to nurse and feed them even though she does not eat or drink anything during those months.
Compared with winter hibernation of animals such as woodchucks, squirrels, snakes, frogs, and so forth, the winter sleep of many bears is only a series of naps. This is because the slumber of bears in the winter may be disturbed, as their body temperature stays high and their breathing remains at the normal rate. Some will even awake on their own accord in the winter and prowl around for a few hours or days at a time.
Scientists in Yellowstone Park discovered that grizzly bears were likely to choose dens where they would not likely be disturbed. Some of the dens were right on canyon walls where it would be very difficult for access by anyone or anything. All of the dens that were on slopes faced north, so that warm spells would not warm up the den and awake the sleeping bear. The dens were cozily lined with a fine insulation of pine and fir boughs.
It has also recently been discovered that grizzly bears would not enter their dens for hibernation until the onset of a blizzard, the type of blizzard that would quickly cover their tracks as they entered into their dens. This would serve as a fine protection for them during their hibernation, as no one would know that there was a sleeping bear deep inside of that den.
It would not be very practical for bears to refuse to play their roles in preparation for their hibernation necessary for their survival of the harshness of winter. In fact for them to ignore this would literally mean death for them. However, bears are not of such intelligence to appreciate the signs of approaching winter, but they act on an inbuilt instinct that moves them in such a way for their self-preservation.
Where man can read the signs of the weather, and can note on a calendar to see when winter is approaching, the bear does not have the same kind of intelligence.
However, for them to hibernate means their survival. These cold changes in the winter months can be taken for granted by man. Yet, for animals it is a time of great changes.
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