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Hibernation is an inactive, sleep like state that animals must go and at least one bird enter during the winter. Animals that hibernate shelter themselves from harsh winter and reduce their need for food. Their body temperatures are considerably lower, as well as their heartbeat and breathing. The true hibernator spends most of the winter in a state close to death; in fact the animal may appear to be dead. The body temperature is close to zero degrees; the respiration is only a few breaths per minute; and the heartbeat is so slow and gradual as to be barley perceptive. An animal in this state requires little energy to stay alive, living off the fat stored in the organism's body. Warm-blooded hibernators eat large amounts of food in the fall season, storing fat in preparation for the long rest. However they do not sleep straight through the winter. These animals experience several bouts, or periods of deep hibernation alternating with periods of wakefulness. They're able to arouse themselves from hibernation at any time and may also be awakened in varying temperatures. A few clever mammals may even store food in their caves or burrows, enjoying a midnight snack between these times of insomnia. Scientist have discovered a chemical present in the blood of hibernating animals, hibernating induces trigger (HIT), developed during the active, warm summers. This type of chemical generates the need to hibernate as winter arrives. Among mammals, true hibernators ore found only in the orders, chiropera, inscetivoria, and rodentia.
Cold blooded hibernators; (i.e.anphibians and reptiles) hibernate when the cold weather causes the animals temperature to drop. Since the animal's temperature fluctuates to adjust to the environment the organism inhabits, the animal can only be aroused from hibernation when the environment warms up enough to heat the body. Although this type of activity cannot truly be called hibernation, but experiencing a state of torpor resulting from a rise in the body temperature. During the spring and summer when snakes, for example, are out of the hibernation stage, they will be less active on cooler days, you will see a drop in body temperature and slower heart rate.
Some animals "sleep" in awkward positions. An example of this would be a bat. Bats hang by their hind feet when sleeping or hibernating and their wings and tail curl close to the body for added insulation. Many species of bats huddle together when hibernating, reducing the amount of body surface in an area. Unlike other hibernators, they're confined to a single nest. Bats hibernate in caves and secluded dark places. The temperature is not the same throughout the cave, and bats wake from time to time to seek a more suitable resting-place.
In animals that hibernate curled into a ball, the region of the heart is slightly warmer than the rest of the body. The position must enable blood to flow to the abdomen, but deep rectal temperature is slightly lower than the heart. In bats, no difference in temperature has been detected in different parts of the body.
In the next few pages, I will discuss several organisms that hibernate, including their mannerisms and other fascinating occurrences while in the torpid state.
Characteristics of Hibernation
Hibernating mammals breathe slowly and evenly, and their temperatures approach that of their environment and fluctuate with it. In the studies of the thirteen lined squirrel, Citellus triddcemlineatus, during the ordinary, active life of this squirrel resperates 100 to 200 times per minute, or even 300 times when exited. Its heartbeats 200 to 350 time per minute, or up to 380 times when exited and its body temperature may range from 32 to 41 degrees Celsius. But while hibernating it may breath as seldom as once or twice per minute or even less. Its heart then beats only about 5 times per minute and its temperature drops almost as low as the air surrounding it. Hibernating insects, as well as toads and frogs, reptiles, and mammals, have in most cases, laid up internal supplies of fat. It is concentrated in layers or various shaped bodies, of which the multifingerd fat bodies of frogs and toads are most familiar. Woodchucks, bears, and other mammals are famous for the large appetites that are very efficient help in storing fat.
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Biology, Sleep, Animal physiology, Physiology, Biota, Hibernation, Ethology, Thermoregulation, Torpor, Groundhog, Bat, Dormancy
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