Hibernation Essay, Research Paper
Hibernation: Definition 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 HibernationHibernating 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. Although they may appear entirely lifeless, hibernating organisms are in generally quick and sensitive in handling changing temperatures and other factors. If a dormant, curled up chipmunk, Marmota Monax, is touched lightly with a pencil point, its muscles will at once contract, and the ball of fur will instantly tighten.Length of Hibernation In Most of Northern United States, the general period of animal hibernation extends from late October or mid November to the later part of March or April, though various species enter hibernation early and come out later. Chipmunks postpone their retirement even up to December according to the temperature, but woodchuck retreat into their holes regularly about the last of September. Temperatures, sexes of organisms, and food availability play as variables in the entrance into hibernation. Favorable Hibernating Areas More small animals find good hibernation areas in forests on leaf covered ground and in the first three feet below the ground surface. All sorts of shelters have been made or natural ones appropriated for hibernation: caves and rocky dens, hollow trees, holes in the earth and endless varieties of little burrows in the soil, muddy pond bottoms, in the bark of trees, within plant stems, in leaf buds and seeds, little tucked-in retreats among grass and leaves, and crevasses in buildings. Causes of Hibernation
Of the mammals in the Northeastern United States, only the bats, black bears, raccoons, woodchucks, chipmunks, red squirrels, and jumping mice become dormant in the winter. Observers of hibernating mammals agree that the cold, hunger, darkness, and quiet are important influences in bringing on hibernation. Animals inherit patterns of structure and habitat, which are not easily changed by what goes on around them. The habitat of hibernation is one of these. These influences of heredity and environment cause the animal to hibernate. Sometimes, and in some animals more than in others, heredity seems most influential. Cold is the first importance among environmental influences. Hibernators commonly begin to grow drowsy as the temperature drops to about 50 degrees farinheight. Their body temperature falls and they drift into a deeper and deeper sleepiness. Even in the same species, of the same part of the country, there may be considerable variations in the date which animals enter and emerge from hibernation. Scarcity of food helps bring on hibernation. In nature, woodchucks, chipmunks, and others commonly hibernate when food is plentiful. Darkness and quiet are probably more essentials to hibernation. Like other animals, mammals seek quiet spots and subdued light or darkness for their sleeping places. Weather they are skunks, chipmunks, raccoons, or woodchucks they will eventually retire to their own special burrow or some other dark place removed from noise and disturbance for the long duration. Preparation for Hibernation Mammal’s unconscienecly prepare for hibernation by weeks of heavily eating and fatting. By fall, woodchucks have laid layers of fat around their chest and shoulders, on the axles of their legs, and internal organs and muscles, which they will use for warmth. Very fat individuals of a species often hibernate earlier than their thinner relatives. The fattest ones stay in hibernation the longest. Some hibernating mammals start the winter with food stored in their nest, as well as large accumulation of fat in their bodies. While they are hibernating, mammals may not take any food for months, although they may awaken and eat irregularly. Entrance into Hibernation Weather they are wasps or toads or woodchucks, animals go into hibernation slowly, often a step at a time, awaken after their first drowsiness, then sleeping once more, perhaps repeating this several times rather than suddenly slipping into a long-continued sleep. The 13-lined ground squirrels studied also approached hibernation slowly. As they gradually sank into drowsiness, their body temperatures fell from 1 to 5 degrees per hour and later from 6 to 7 degrees per hour. Though when they are awakening, their body temperature rises at the rate of 20 degrees in 35 minutes. Hibernation The hibernating animals lie in stillness resembling ordinary sleep, but really it’s very different from it. Mammals are motionless except for their breathing the majority adopts some curled-up position, usually with the head between the hind legs so their eyes are hidden. The 13-lined ground squirrel sets on the posterior surface of its hind legs with its back arched and its head bent at a sharp angle so the nose rest against its abdomen. Hibernating mammals may be motionless for days at a time and occasionally may be handled freely without awakening. Even when in deep topor, hibernating animals are much more susceptible to noise, touch, and other disturbances. On the other hand, ground squirrels can be handled gently and a thermometer put into their cheek pouches without awaking them. Mammals in deep hibernation breathe very slowly and irregularly, body temperature falls low, and the heart beats slowly and irregularly. There are some indications that woodchucks, ground squirrels, and perhaps some other mammals may show an unequal distribution of the blood during hibernation. This, intern, causes the animals temperature to fall into the low levels characteristics of hibernation. Awakening from HibernationThe process of awakening from hibernation is rapid and evolves sudden increases in bodily activity and temperature, exceeding that of the ordinary active animal. When it is in deep hibernation, the woodchuck heart beats four or five times per minute; but as it awakens the rate may increase to 200 times per minute, which is faster than normal. As woodchucks emerge from hibernation the respiration rate rises from the average once a minute or less of hibernation to a rate above the 25 to 30 times per minute of nonhiberation. The heat mostly from the fat remaining in the body rises like a fever from hibernation. Such heights may be maintained for half an hour or so.In conclusion, hibernation is truly an amazing process with many factors involved. The interaction between animal and environment has been studied for thousands of years. It will continue as one of the most fascinating issues to be discussed in books and literature. IntroductionThe topic I was so graciously blessed with was the fascinating process of hibernation. From the time the embryo is formed to the time of death, certain animals take part in this annual sleep, if you will. The pages proceeding will cover the following subtopics: Hibernation: Definition, Characteristics of Hibernation, Length of Hibernation, Favorable Hibernation Areas, Causes of Hibernation, Preparation for Hibernation, Entrance into Hibernation, Hibernation, and Awakening from Hibernation. Several organisms also received commentary: the common brown bat (eptesicus fuscus), woodchuck (marmota monax), eastern chipmunk (tamias striatus), greater horseshoe bat (rhinolophus ferrumequinum), and the 13-lined squirrel (cittelus tridecemlineatus).
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