Why do mammals hibernate?

Question

I am doing some science homework... and I need help!

Answer 1

Hibernation is a necessary means of surviving the dark, cold months of winter. For species such as the hedgehog hamster, and brown bat, the only alternative is starvation. Hibernation – a long winter sleep – enables some warm-blooded animals to survive the months when their food supplies become unreliable or disappear altogether. True hibernators save precious energy by reducing their body temperature to a level that would normally prove fatal.

Why Hibernate? During the winter, most plants stop growing, and cold-blooded animals such as insects become inactive. Warm-blooded animals – birds and mammals – cannot respond in the same manner. Although some animals can survive even in the below freezing conditions if Antarctica, they all must keep their body temperatures constant within very narrow limits. If their temperatures rise or fall beyond these limits, the animals will die.

For most animals, keeping warm presents the greatest challenge in winter, because the body temperature of birds and mammals is almost always higher than the surrounding air temperature. Maintaining a high body temperature requires energy in the form of food – and food is scarce in most places in winter. Many animals that live in the extreme cold of the world’s polar regions conserve energy by growing thick winter coats. The husky, a hardy breed of dog that lives in the polar regions, grows a coat so thick and warm that it can sleep on the snow in temperatures that may get as low as –22 degrees.

Smaller animals lose heat more quickly and must burn their food faster to stay warm. A mouse, for example, burns energy 20 times faster than a sheep. Furthermore, there is a limit to how thick a coat a small animal can grow. As a result, many smaller animals build themselves snug, well-insulated nests, often in deep, underground tunnels.

For a warm-blooded mammal to keep its body temperature at 100 degrees, it must eat. Some species of mouse build up reserves of fat on which they rely when food becomes scarce. Other animals live on stored supplies of nuts and seeds. For many, especially those that feed mainly on insects, the only way to survive is to reduce their energy by hibernating.

What is Hibernation? Throughout the summer, small, warm blooded animals such as ground squirrels and marmots keep their body temperature at about 99 degrees, no matter what the air temperature is. Their breathing and heartbeat are also quite normal at approximately 16 breaths and 88 beats per minute.

As soon as winter comes and the temperature drops, the marmot curls up and falls into what appears to be a deep sleep but is actually hibernation. This is a state that the animal enters deliberately, and during which it retains some control over its body temperature. Such control allows the animal to revive itself periodically when it needs to eat, or if some emergency arises, such as its nest’s becoming flooded. During hibernation, the marmot’s body temperature drops to 50 degrees – low enough to be fatal to any non-hibernating species.

A Restless Sleep: Hibernators do not remain constantly asleep throughout the winter. Small bats hibernate for the longest periods, but even they remain dormant for no longer than a month. The hedgehog, by comparison, hibernates for only several weeks before waking briefly. At the other extreme, the tiny shrew, which weighs barely two grams, hibernates for less then eight hours at a time, and its body temperature falls to just 64 degrees. While hibernating, some animals may appear to be dead. They are cold to the touch and seem lifeless. Other species wake almost instantly if they are disturbed.

Almost all hibernators will wake up when the temperature falls below the point from which they could not recover. Waking is usually accompanied by shivering as the animal begins to raise its body temperature. Although constant reawakening uses up energy, it seems vital to the animal’s survival. Since the animal uses some energy during hibernation, the resultant waste products must be expelled.

Mammals That Hibernate:
True Hibernators: Only true hibernators are able to lower their body temperature to near freezing and then generate enough warmth to revive themselves. Both the echidna and the duck-billed platypus hibernate for several periods of 5 to 10 days. The koala and the Tasmanian pygmy opossum are two of the few marsupials that are true hibernators. The majority of true hibernators are either rodents or bats. Rodent hibernators include ground squirrels, marmots, woodchucks, dormice, and hamsters. The hedgehog spends the cold winter months curled up in a nest of dried leaves. Among bats, hibernators include the noctule and serotine bats that spend the winter in deep, damp caves, wrapped in their wings.

Winter Sleepers: Certain large mammals such as American black bears spend much of the winter asleep in their dens, but they are not true hibernators. Although their heartbeat slows to just 10 beats per minute, their body temperature is actually maintained at 86 degrees. Badgers, raccoons, and skunks also sleep through cold spells, but they, too, must maintain relatively high body temperatures.

Hibernation in Birds: It was once thought that swallows spent the winter underwater, hibernating at the bottom of rivers and ponds. But it is now known that they migrate south to warmer climates each fall. More recently, however, it has been discovered that certain species of bird do appear to hibernate, if only for short periods of time. The white-throated poor will feeds on insects, and when they become scarce in winter, it hibernates. For several hours at a time, its body temperature drops from 104 degrees to as low as 43 degrees. Several species of tropical hummingbird also appear to hibernate for a few hours each night, when their body temperature falls to 46 degrees.

Answer 2

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Answer 3

This Site Might Help You.

RE:
Why do mammals hibernate?
I am doing some science homework... and I need help!

Answer 4

I have no idea about this, though i feel it may be because to them summer is like a really big meal and, if they are like me, they just wanna sleep all day afterwards.

If they had kids/bosses/wife's/drunk mates etc, they would get no sleep.

Hence we are victims of our own success.

However, that is not why i am here.

You answered my question on Green Britain.

Are you on speed or what?

My country being described by you is not the one I live in!!

Though I wish it was.

Please, tell me how you came to get those ideas, I am intrigued.

Oh, and give Mark B the points.

Answer 5

To survive weather that is too cold to live in.

Answer 6

Dang, you woke me up! Now I'm hungry.

Answer 7

Bears do When I last checked they were rather big.

Answer 8

I think its for energy in the spring when they wake up. because they have nothing to do in the winter