Polar bears hibernate. Do polar bears hibernate? Causes of hibernation in bears
There are many types of bears in the world, but those who fall into hibernation climatic zones temperate to arctic. This is due to the nature of animal nutrition. In these areas, the snow falls in a dense layer and on long time. Bear is a predator, the weight of animals ranges from 150 (small individuals) to 750 kg. Such a huge beast needs a large number of food.
If we talk about hibernation, during this process, all vital signs are practically reduced to zero. The body temperature of the animal drops and becomes only slightly higher than the air surrounding it. This is what reduces energy consumption. If external factors environment change, for example, if the temperature in the den drops, then the animal wakes up, warms up (burrowing into the snow or bedding) and falls asleep again. Thanks to this, it is possible to save more heat, therefore, there will be less energy consumption, and the bear will safely endure in order to get out into the forest again in the summer.
Features of hibernation
It is known that not all bears dive into. Polar are different from their European relatives. While the rest are quietly sleeping in their dens, they are actively looking for food. An exception to the rule are those who hibernate for several months until they have babies. After birth, the female bear leaves the den and continues active life in search of food.
It is better to never wake up a bear sleeping in a den, as a clubfoot wakes up at one moment, while it becomes 100 times more dangerous. Such cases are extremely rare for a person to stumble upon in the winter. Bears choose very secluded places in the forest, where, perhaps, a human foot has not even set foot.
Scientists have been trying to unravel the mystery of the forest giant for more than a year. After all, it has not yet been definitely identified, which allows them to be in complete hibernation for up to 7 months. By answering this question, scientists hope to make substances used by animals and for humans. This, in turn, will help a person safely fall into a long sleep without harm to the body. One way or another, all this is just a development, but for now people are left to envy the heroic dream of a bear.
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Harsh winters- is one of the most difficult periods animal life. During this period, many animals try to hide in warm places because they have a self-preservation instinct. A particularly striking example of how animals while away the cold season is the hibernation of brown bears, which allows them to pass all frosts and bad weather.
Instruction
Winter sleep is main feature bears and many other animals (badgers, hedgehogs, moles, frogs, reptiles, etc.), which is a kind of measure of their protection from long and cold winters. During winter sleep, the body of animals begins its complete restructuring: breathing becomes rare, the heartbeat slows down, and the body temperature drops. Animals go into suspended animation.
If we talk about bears, then they fall into this state because they do not bother to make any supplies for the winter in time, as squirrels, hamsters and other animals do. Despite the fact that bears are predators of impressive size, their main food in summer period are berries, mushrooms, plants that disappear with the advent of cold weather.
In addition, over the summer, bears gorge themselves and accumulate a huge layer of subcutaneous fat, which will be enough for them not to want to eat during hibernation. It is the accumulated fat reserve that allows the bear to forget about winter sleep for whole months, not remembering severe frosts and winter hunger. Of course, there is a possibility that berries or other fruits will be under the snow, but they will not be able to satisfy the hunger of the beast, whose weight can reach half a ton. It is curious that some types of bears before " winter vacation» take care of the arrangement of their lair. So, they equip their winter dwelling with branches and twigs.
It is worth noting that not all bears forget their winter sleep just to survive hunger. For example, female polar bears fall into being. It is curious that this process in polar bears can occur at any time of the year, but most often it happens, the bears suck them.
However, polar bears are forced to hibernate and the reason for this is the need to produce offspring. In habitat polar bears survival requires a significant layer of fat, which newborns do not have. That is why polar bears make large dens in snowdrifts, in which the temperature never drops below 0°C. Thus, cubs, warmed by the warmth of their mother, can gain weight by eating full-fat milk. Polar bears spend about 6 months in polar bears so that the cubs can get strong enough to live in a frozen world where ice reigns all around.
Wintering of the brown bear
Brown bears hibernate regardless of gender, but still females of this species have their own unique features. She-bears breed in a den, but in order to put on fat, they need to take advantage of all the nutritional opportunities that are available in the summer. Female bears are early, but at the same time they are able to postpone the offensive. Thus, they calculate the time for the cubs to appear in the den, protected from predators.Bears prefer to equip dens not in cold snow, but under large snags of ancient trees or in specially dug cavities in ravines. The temperature in the lair can reach +5-8°C. The she-bear slows down her metabolism, lowers her body temperature by several degrees, which allows her to significantly save energy.
Surprisingly, the bear's sleep is extremely sensitive, so the slightest movement above makes her open her eyes. From 2 to 4 appear in the den, which feed on milk. brown bear spends in the den for up to 5 months. After leaving the den, the female spends some time near her winter shelter so that the cubs can develop muscles for long walks through the forest thicket.
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Many people think that animals hibernate because the weather gets cold where they live. And since the polar bear lives where it is very cold, he must certainly hibernate. But animals hibernate because food supplies are scarce in winter. They don't put away supplies for the winter, but instead go to bed. At this time, a store of fat is stored on their body, which they gradually eat all winter. During hibernation, all life processes almost stop. The body temperature drops, breathing slows down, the heart beats weakly.
Does the same thing happen to polar bears? The answer to this question is negative. In winter, polar bears sleep more than in summer, but this is not the well-known hibernation of animals. The temperature and breathing of polar bears remain normal. They sleep in burrows and caves made of snow and ice. During warming, bears can roam all day and even at night.
Female polar bears sleep more in winter than males. They lie in a den, they are sometimes covered with snow for weeks. During this winter sleep, cubs are born. They are very small at birth, weighing between 170 and 230 grams. Therefore, the mother bear takes care of them somewhat winter months. In the spring, hibernating animals wake up from changes in temperature, humidity, and hunger. They crawl out of their dens and begin to feed.
Everything about everything. Volume 5 Likum Arkady
Do polar bears go into hibernation?
Many people think that animals hibernate because the weather gets cold where they live. And since the polar bear lives where it is very cold, he must certainly hibernate. But animals hibernate because food supplies are scarce in winter. They don't put away supplies for the winter, but instead go to bed. At this time, a store of fat is stored on their body, which they gradually eat all winter. During hibernation, all life processes almost stop. The body temperature drops, breathing slows down, the heart beats weakly.
Does the same thing happen to polar bears? The answer to this question is negative. In winter, polar bears sleep more than in summer, but this is not the well-known hibernation of animals. The temperature and breathing of polar bears remain normal. They sleep in burrows and caves made of snow and ice. During warming, bears can roam all day and even at night.
Female polar bears sleep more in winter than males. They lie in a den, they are sometimes covered with snow for weeks. During this winter sleep, cubs are born. They are very small at birth, weighing between 170 and 230 grams. Therefore, the mother bear takes care of them for several winter months. In the spring, hibernating animals wake up from changes in temperature, humidity, and hunger. They crawl out of their dens and begin to feed.
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Do polar bears hibernate? April 14th, 2018
What is the closest relative? brown bear. They descended from common ancestors who lived only 150 thousand years ago (for the evolution of species, this is quite recent). The brown bear perfectly hibernates in the winter, and can the polar bear sleep in the den in the summer?
And in general, if the dens polar bear?
Surprisingly, almost no sleep! That is, they sleep normally, just like in summer (only in summer they usually sleep more). But they do not fall into winter sleep. (“Hibernation” of bears is more correctly called winter sleep; bears do not have real hibernation, since their body temperature almost does not drop, and at any moment they can wake up.) Only pregnant and nursing females fall into winter sleep. The rest of the polar bears, if they lie in dens, then not for long and not every year.
The main food of polar bears is seals. These are such seals. They are hunted by polar bears on the ice. They either snatch the seal with their paw from the hole in the ice through which the seal breathes, or lie in wait and grab the seals that have climbed out onto the ice to rest. In many areas of the Arctic where polar bears live, the ice almost completely melts by the end of summer. They can no longer hunt seals. On land, most arctic animals are able to run away from a polar bear, and in the sea they can swim away from it. It is good if you manage to find the carcass of a dead whale or walrus on the shore. And if not, then at the end of summer and autumn, bears sometimes go hungry for several months. So in winter they do not sleep, but start hunting again as soon as the ice appears.
But the females have nowhere to go - they have to lie in dens. After all, polar bear cubs, like other bears, are born small (their mass is less than a kilogram) and blind; they are covered only with short down. Usually females arrange a lair on the shore, sometimes 50 km from the seashore. As a rule, a she-bear makes a lair in a snow dune, but if there is little snow, she can also dig a hole in frozen ground. The female lies in the den just when the ice melts and it becomes difficult to hunt. Bear cubs are usually born in November-January, and remain in the den until February-March. Before the birth of the cubs, the mother bear really mostly sleeps, but during childbirth she wakes up, and after childbirth she has to sleep less. However, she is still in a state of winter sleep before leaving the den: she does not eat, drink, pee or poop.
How does the female manage to accumulate nutrients for a long sleep and for feeding cubs (and there are usually two of them)? It turns out that polar bears mate in the spring - in April-May. Immediately after mating, pregnant females begin to eat so intensely that by autumn they become 200 kg heavier - their weight sometimes almost doubles! At the same time, the development of embryos in the abdomen of a bear in the spring stops at early stage and continues only in autumn; before that, they are at rest (scientifically called embryonic diapause). Apparently, this allows female bears to "adjust" the beginning of embryo development to the time of entry into the den; after all, this time depends greatly on the conditions in a given area and even on the weather in a given year.
It is not very clear why all the polar bears should not eat too much. But for some reason they don't.
It is interesting that, apparently, at any time of the year, during prolonged starvation, polar bears seem to “sleep on the go.” In their blood, the concentration of urea drops sharply, which is typical for other types of bears during hibernation. Bears are able to use urea for the synthesis of amino acids and proteins of the plasma (liquid part) of the blood. (Plasma protein concentration should be as constant as possible, otherwise various problems with the transport of fluids and metabolism in the body.) In addition, the lower the urea content, the less it needs to be excreted in the urine, which means that you need to drink less. Although water in the form of snow is usually readily available in the Arctic, drinking (or rather, eating) it is energetically unprofitable - a lot of energy is wasted on warming it.
If a brown bear's urea concentration has dropped, it becomes lethargic, no longer wants to eat, and falls asleep. But the polar bear, in the presence of food, begins to eat again and raises the concentration of urea to a normal level.
Interestingly, during the period of winter sleep, the polar bear somehow manages to almost not lose bone and muscle mass. Usually, in humans and other animals, their mass decreases sharply with prolonged immobility, even when there is food; the mass of bones and muscles also decreases in other species of bears during sleep. But the polar bear consumes almost only fat. It turns out that in some respects, polar bears are more adapted to winter sleep.
sources
Surprisingly, almost no sleep! That is, they sleep normally, just like in summer (only in summer they usually sleep more). But they do not fall into winter sleep. (“Hibernation” of bears is more correctly called winter sleep; bears do not have real hibernation, since their body temperature almost does not drop, and at any moment they can wake up.) Only pregnant and nursing females fall into winter sleep. The rest of the polar bears, if they lie in dens, then not for long and not every year.
And this is surprising because the polar bear is the closest relative of the brown bear. They descended from common ancestors who lived only 150 thousand years ago (for the evolution of species, this is quite recent). Even in wild nature these species sometimes interbreed. At the same time, in their way of life, polar bears differ sharply from brown ones.
The main food of polar bears is seals. These are such seals. They are hunted by polar bears on the ice. They either snatch the seal with their paw from the hole in the ice through which the seal breathes, or lie in wait and grab the seals that have climbed out onto the ice to rest. In many areas of the Arctic where polar bears live, the ice almost completely melts by the end of summer. They can no longer hunt seals. On land, most arctic animals are able to run away from a polar bear, and in the sea they can swim away from it. It is good if you manage to find the carcass of a dead whale or walrus on the shore. And if not, then at the end of summer and autumn, bears sometimes go hungry for several months. So in winter they do not sleep, but start hunting again as soon as the ice appears.
But the females have nowhere to go - they have to lie in dens. After all, polar bear cubs, like other bears, are born small (their mass is less than a kilogram) and blind; they are covered only with short down. Usually females arrange a lair on the shore, sometimes 50 km from the seashore. As a rule, a she-bear makes a lair in a snow dune, but if there is little snow, she can also dig a hole in frozen ground. The female lies in the den just when the ice melts and it becomes difficult to hunt. Bear cubs are usually born in November-January, and remain in the den until February-March. Before the birth of the cubs, the mother bear really mostly sleeps, but during childbirth she wakes up, and after childbirth she has to sleep less. However, she is still in a state of winter sleep before leaving the den: she does not eat, drink, pee or poop.
How does the female manage to accumulate nutrients for a long sleep and for feeding cubs (and there are usually two of them)? It turns out that polar bears mate in the spring - in April-May. Immediately after mating, pregnant females begin to eat so intensely that by autumn they become 200 kg heavier - their weight sometimes almost doubles! At the same time, the development of embryos in the belly of a she-bear stops at an early stage in spring and continues only in autumn; before that, they are at rest (scientifically called embryonic diapause). Apparently, this allows female bears to "adjust" the beginning of embryo development to the time of entry into the den; after all, this time depends greatly on the conditions in a given area and even on the weather in a given year.
It is not very clear why all the polar bears should not eat too much. But for some reason they don't.
It is interesting that, apparently, at any time of the year, during prolonged starvation, polar bears seem to “sleep on the go.” In their blood, the concentration of urea drops sharply, which is typical for other types of bears during hibernation. Bears are able to use urea for the synthesis of amino acids and proteins of the plasma (liquid part) of the blood. (Plasma protein concentrations should be as constant as possible, otherwise various problems with the transport of fluids and metabolism in the body arise.) In addition, the lower the urea content, the less it needs to be excreted in the urine, which means less need to drink. Although water in the form of snow is usually readily available in the Arctic, drinking (or rather, eating) it is energetically unprofitable - a lot of energy is wasted on warming it.
If a brown bear's urea concentration has dropped, it becomes lethargic, no longer wants to eat, and falls asleep. But the polar bear, in the presence of food, begins to eat again and raises the concentration of urea to a normal level.
Interestingly, during the period of winter sleep, the polar bear somehow manages to almost not lose bone and muscle mass. Usually, in humans and other animals, their mass decreases sharply with prolonged immobility, even when there is food; the mass of bones and muscles also decreases in other species of bears during sleep. But the polar bear consumes almost only fat. It turns out that in some respects, polar bears are more adapted to winter sleep.