This research paper explains the hibernation and denning habits of the Grizzly bear. I will talk about the bear's temperature and heart rate during hibernation, how long they stay in the den and how they can hibernate that long without eating or drinking anything.

The Grizzly bear has a heavy body with relatively short legs, neck and tail. It has a large head with rounded ears and unusually small eyes for such a large animal. It has a heavy coat, padded by several inches of fat which creates the illusion of a slow and clumsy animal. But, this is not the case. A Grizzly bear can reach a speed of 35 or 40 mph for short distances. This is fast enough to catch a running horse and kill it with a blow of its forepaw. Most bears can only leap a few feet off the ground. Some bears are good climbers, and all are capable swimmers.

The color of Grizzly bears throughout Alaska differs widely from area to area. Some Grizzlies are black with silver-tipped hairs and some have pale blond or yellow hair. Most Grizzlies are a shade of brown or gray-brown. Bears that have blond bodies and dark legs are more common. Male Grizzlies tend to be darker than females. Cubs usually have a white color that lasts through the first summer. There is only one other bear that can be mistaken for a Grizzly bear, and it is the Black bear.

Adult Grizzly bears are huge, but do differ in size,depending on their

Age, sex, time of year and geographic location. Coastal Grizzlies are reported to be larger than interior Grizzlies. Interior Grizzlies are about one-third smaller than Coastal Grizzlies. Females in the same area normally weigh about half as much as the male. Grizzlies weigh about 20 to 30% more in the fall before going into hibernation. A coastal Grizzly may grow to be eight or nine feet and stand more than four feet at the shoulders and weighing up to 1,500 pounds. Interior Grizzlies are much smaller.

The skull of a bear from the coastal area reaches 98% of its length by the age of 10 years and 98% of its width by the age of 12 years. Skull sizes of the Grizzlies are the largest and widest from the Kodiak island area and the Alaska Peninsula.

The hearing and smelling of a Grizzly is far better than its eyesight. The Grizzly bear has difficulty defining man when standing still. Grizzly bears are normally shy except when hungry, disturbed or attacked by something. Nothing can challenge a bear except a man's rifle.

The Grizzly bear hibernates every year. A Grizzly bear's instinct to den is an adaptation to life in places where conditions might otherwise threaten survival. There has been an argument between scientists as to whether bears are true hibernators. When it hibernates the Grizzly has a body temperature of less than 10 degrees Fahrenheit and its hear rate is eight beats per minute. Normally, before entering the den it is 40 beats per minute.

The Grizzly bear does not eat, drink, defecate or urinate during its

entire hibernation period which can be up to six months or longer. It produces metabolic water from fat and doesn't produce products that cause it to urinate. Considering the evidence from Grizzly and rodent studies, Grizzlies are better hibernators in a functional sense.

The Grizzly may spend from two to seven months at the den sites or in the dens. It stays in its den during the winter because of the decreased food supply in winter. Grizzly dens are usually found in high snow accumulation areas on mountain slopes. The hibernation period is usually from October to April. Before hibernating, the bear may dig out its den long before it retires to it. Most bear dens are three feet wide at the entrance, five feet long, four feet wide and four feet high. The bears don't usually use the same den twice. They look for den sites where roots of trees can support the den, or in a low cave, a hollow tree or in the shelter of a brush pile. Sometimes an earthen den is dug directly into the ground. The bears work on their den sites just as birds work at building their nests. Bears seem to learn by experience. Older Grizzlies are likely to choose more suitable sites, and the younger bears choose dens that aren't as suitable as those of experienced bears'. Grass, moss and evergreen boughs are carried inside to line the den.

Denning time generally coincides with the first signs of winter weather. During late summer, Grizzly bears have been known to eat 20,000 calories a day to reserve fat for hibernation. This is like a human being eating 38 banana splits or 42 hamburgers each day. As a result, Grizzlies weigh 20-30% more before going into hibernation than when they come out in the spring.

The first Grizzly to go into its den is a pregnant female. The pregnancy is perfectly timed with the period of hibernation. After a period of time, snow piles over the entrance of the den and obliterates all traces of the bear. The den of the hibernating Grizzly is almost like a tomb if you ever get a chance to look inside. And when the bear is in hibernation, it hardly looks like a living mammal. But, there is indeed life in the den. And a second little life is growing during hibernation in the pregnant female. If this is her first pregnancy she will probably have one cub, but if it is her second or third pregnancy she will probably have two or three cubs.

In summation, the Grizzly bear is a fascinating animal with an amazing ability to adapt to many different climates and topographies. One characteristic which allows it to survive throughout its range is its instinct to hibernate. Hibernation allows it to conserve its energy during the harshest season, winter, and to emerge in good health for another year in the wild.

BIBLIOGRAPHY

BLEDSOE, T. Brown Bear Summer. 1987.

MURIE, A. The Grizzlies of Mount McKinley. 1981.

HERRERO, S. Bear Attacks. 1985.

REARDEN, J. Alaska Mammals. 1981.

DOMICO and NEWMAN. Bears of the World. 1988.