Do polar bears hibernate in winter or not? Do polar bears sleep in winter? What is bear hibernation?
Only pregnant females and those nursing newborn cubs fall into winter sleep. The rest of the polar bears, if they lie in dens, do so only for a short time and not every year.
Surprisingly, they barely sleep! That is, they sleep normally, just like in the summer (only in the 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 hardly drops, and they can wake up at any moment.) Only females who are pregnant and nursing newborn cubs fall into winter sleep. The rest of the polar bears, if they lie in dens, do so only for a short time 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 (this is very recent for the evolution of species). Even in the wild, these species sometimes interbreed. At the same time, in their way of life, polar bears differ sharply from brown bears.
The main food of polar bears is seals. These are such seals. Polar bears hunt them on the ice. They either snatch the seal with their paw from a hole in the ice through which the seal is breathing, or they lie in wait and grab 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 escape from polar bear, and into the sea - to swim away from it. It’s good if you can find the carcass of a dead whale or walrus on the shore. And if not, then at the end of summer and autumn the bears sometimes starve for several months. So in winter they do not sleep, but start hunting again as soon as ice appears.
But the females have nowhere to go - they have to lie down in dens. After all, polar bear cubs, like other bears, are born small (their weight is less than a kilogram) and blind; they are covered only with short fluff. Usually females make a den on the shore, sometimes 50 km from the seashore. As a rule, a bear makes a den in a snow dune, but if there is not enough snow, she can dig a hole in frozen ground. The female lies down in a den just when the ice melts and hunting becomes difficult. Cubs are usually born in November-January, and remain in the den until February-March. Before the cubs are born, the mother bear actually sleeps mostly, but during childbirth she wakes up, and after giving birth she has to sleep less. However, before leaving the den, she is still in a state of winter sleep: she does not eat, does not drink, does not pee or poop.
How does a female manage to accumulate nutrients for 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 feed 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 bear’s abdomen in the spring stops at early stage and lasts only in autumn; Before this, they are in a state of rest (this is scientifically called embryonic diapause). Apparently, this allows female bears to “adjust” the onset of embryo development to the time they enter the den; after all, this time greatly depends on the conditions in a given area and even on the weather in a given year.
It’s not very clear why all polar bears shouldn’t eat their fill in the same way. But for some reason they don't do this.
It is interesting that, apparently, at any time of the year, during prolonged fasting, polar bears seem to “sleep on the move.” The concentration of urea in their blood drops sharply, which is typical for other species of bears during hibernation. Bears are able to use urea to synthesize amino acids and proteins in the plasma (liquid part) of the blood. (The concentration of proteins in plasma should be as constant as possible, otherwise various problems with fluid transport 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 the less you 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 lost to warm it.
If a brown bear's urea concentration has decreased, it becomes lethargic, no longer wants to eat, and falls asleep. But when food is available, the polar bear begins to eat again and raises the urea concentration to normal levels.
It is interesting that during the period of winter sleep, the polar bear somehow manages to lose almost no mass of bones and muscles. Usually in humans and other animals their weight 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 uses almost only fat. It turns out that in some respects polar bears are better adapted to winter sleep.
There are many species of bears in the world, but those that hibernate climatic zones temperate to arctic. This happens due to the feeding habits of animals. In these areas the snow falls in a dense layer and on for a long time. The bear is a predator, the weight of animals ranges from 150 (small individuals) to 750 kg. Such to a huge beast need to a large number of food.
If we talk about hibernation, during this process all vital signs are practically reduced to zero. The animal's body temperature drops and becomes only slightly higher than the air around it. This is what allows you to reduce energy consumption. If external factors environment change, for example, if the temperature in the den drops, the animal wakes up, insulates itself (by burying itself in snow or bedding) and goes back to sleep. Thanks to this, it is possible to retain more heat, therefore, there will be less energy consumption, and the bear will safely survive to get out into the forest again in the summer.
Features of hibernation
It is known that not all bears dive into water. Polars differ from their European relatives. While the rest are quietly snoring in their dens, they are actively looking for food. The exception to the rule is that they 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, since the clubfoot wakes up in one moment, and at the same time it becomes 100 times more dangerous. Such cases are extremely rare for a person to come across in winter. Bears choose very secluded places in forest area, where perhaps no human has even set foot.
Scientists have been trying to unravel the mystery of the forest giant for years. After all, it has not yet been precisely revealed what allows them to remain in complete hibernation for up to 7 months. By answering this question, scientists hope to make substances used by animals for humans as well. This, in turn, will help a person safely fall into a long sleep without harm to the body. One way or another, all these are just developments, but for now people can only envy the bear’s heroic sleep.
Video on the topic
Harsh winters- this is one of the most difficult periods animal life. During such a period, many animals try to hide in warm places, because their self-preservation instinct is triggered. Especially a shining example how animals while away the cold season is hibernation brown bears, allowing them to bypass all frosts and bad weather.
Instructions
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 animal's body begins its complete restructuring: breathing becomes rare, the heartbeat slows down, and the body temperature drops. Animals fall into suspended animation.
If we talk about bears, they fall into this state because they do not bother to make any supplies for the winter in a timely manner, as do squirrels, hamsters and other animals. Despite the fact that bears are predators of impressive size, their main food in the summer is berries, mushrooms, and plants, which disappear with the onset of cold weather.
In addition, over the summer bears eat enough food 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 reserve of fat that allows the bear to forget itself in winter sleep for entire months, without remembering the severe frosts and winter hunger. Of course, there is a possibility that there will be berries or other fruits under the snow, but they will not be able to satisfy the hunger of an animal whose weight can reach half a ton. It is curious that some species of bears before " winter holidays“They take care of the structure of their den. So, they equip their winter home with branches and twigs.
It is worth noting that not all bears go into winter sleep only 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 this happens because the bears suck them.
However, polar bears are forced to hibernate and the reason for this is the need to produce offspring. In the habitat polar bears a significant layer of fat is required for survival, 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 feeding on rich milk. Polar bears spend about 6 months in prison so that the cubs can become 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 females of this species still have their own unique characteristics. Mother bears produce offspring in the den, but in order to gain 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 are able to delay the attack. In this way, they time the cubs to emerge in a den protected from predators.Mother bears prefer to make dens not in cold snow, but under large snags centuries-old trees or in specially dug cavities in ravines. The temperature in the den can reach +5-8°C. The 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, feeding on milk. A brown bear spends up to 5 months in a den. 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.
Video on the topic
Surprisingly, they barely sleep! That is, they sleep normally, just like in the summer (only in the 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 hardly drops, and they can wake up at any moment.) Only females who are pregnant and nursing newborn cubs fall into winter sleep. The rest of the polar bears, if they lie in dens, do so only for a short time 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 (this is very recent for the evolution of species). Even in wildlife these species sometimes interbreed. At the same time, in their way of life, polar bears differ sharply from brown bears.
The main food of polar bears is seals. These are such seals. Polar bears hunt them on the ice. They either snatch the seal with their paw from a hole in the ice through which the seal is breathing, or they lie in wait and grab 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 outrun a polar bear, and in the sea, they can swim away from it. It’s good if you can find the carcass of a dead whale or walrus on the shore. And if not, then at the end of summer and autumn the bears sometimes starve for several months. So in winter they do not sleep, but start hunting again as soon as ice appears.
But the females have nowhere to go - they have to lie down in dens. After all, polar bear cubs, like other bears, are born small (their weight is less than a kilogram) and blind; they are covered only with short fluff. Usually females make a den on the shore, sometimes 50 km from the seashore. As a rule, a bear makes a den in a snow dune, but if there is not enough snow, she can dig a hole in frozen ground. The female lies down in a den just when the ice melts and hunting becomes difficult. Cubs are usually born in November-January, and remain in the den until February-March. Before the cubs are born, the mother bear actually sleeps mostly, but during childbirth she wakes up, and after giving birth she has to sleep less. However, before leaving the den, she is still in a state of winter sleep: she does not eat, does not drink, does not pee or poop.
How does the female manage to accumulate nutrients for a long sleep and for feeding her 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 feed so intensively that by autumn they become 200 kg heavier - their weight sometimes almost doubles! At the same time, the development of embryos in the female bear’s abdomen stops at an early stage in the spring and continues only in the fall; Before this, they are in a state of rest (this is scientifically called embryonic diapause). Apparently, this allows female bears to “adjust” the onset of embryo development to the time they enter the den; after all, this time greatly depends on the conditions in a given area and even on the weather in a given year.
It’s not very clear why all polar bears shouldn’t eat their fill in the same way. But for some reason they don't do this.
It is interesting that, apparently, at any time of the year, during prolonged fasting, polar bears seem to “sleep on the move.” The concentration of urea in their blood drops sharply, which is typical for other species of bears during hibernation. Bears are able to use urea to synthesize amino acids and proteins in the plasma (liquid part) of the blood. (The concentration of proteins in plasma should be as constant as possible, otherwise various problems with fluid transport 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 the less you 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 lost to warm it.
If a brown bear's urea concentration has decreased, it becomes lethargic, no longer wants to eat, and falls asleep. But when food is available, the polar bear begins to eat again and raises the urea concentration to normal levels.
It is interesting that during the period of winter sleep, the polar bear somehow manages to lose almost no mass of bones and muscles. Usually in humans and other animals their weight 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 uses almost only fat. It turns out that in some respects polar bears are better adapted to winter sleep.
Surprisingly, they barely sleep! That is, they sleep normally, just like in the summer (only in the 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 hardly drops, and they can wake up at any moment.) Only females who are pregnant and nursing newborn cubs fall into winter sleep. The rest of the polar bears, if they lie in dens, do so only for a short time 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 (this is very recent for the evolution of species). Even in the wild, these species sometimes interbreed. At the same time, in their way of life, polar bears differ sharply from brown bears.
The main food of polar bears is seals. These are such seals. Polar bears hunt them on the ice. They either snatch the seal with their paw from a hole in the ice through which the seal is breathing, or they lie in wait and grab 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 outrun a polar bear, and in the sea, they can swim away from it. It’s good if you can find the carcass of a dead whale or walrus on the shore. And if not, then at the end of summer and autumn the bears sometimes starve for several months. So in winter they do not sleep, but start hunting again as soon as ice appears.
But the females have nowhere to go - they have to lie down in dens. After all, polar bear cubs, like other bears, are born small (their weight is less than a kilogram) and blind; they are covered only with short fluff. Usually females make a den on the shore, sometimes 50 km from the seashore. As a rule, a bear makes a den in a snow dune, but if there is not enough snow, she can dig a hole in frozen ground. The female lies down in a den just when the ice melts and hunting becomes difficult. Cubs are usually born in November-January, and remain in the den until February-March. Before the cubs are born, the mother bear actually sleeps mostly, but during childbirth she wakes up, and after giving birth she has to sleep less. However, before leaving the den, she is still in a state of winter sleep: she does not eat, does not drink, does not pee or poop.
How does the female manage to accumulate nutrients for a long sleep and for feeding her 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 feed 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 female bear’s abdomen stops at an early stage in the spring and continues only in the fall; Before this, they are in a state of rest (this is scientifically called embryonic diapause). Apparently, this allows female bears to “adjust” the onset of embryo development to the time they enter the den; after all, this time greatly depends on the conditions in a given area and even on the weather in a given year.
It’s not very clear why all polar bears shouldn’t eat their fill in the same way. But for some reason they don't do this.
It is interesting that, apparently, at any time of the year, during prolonged fasting, polar bears seem to “sleep on the move.” The concentration of urea in their blood drops sharply, which is typical for other species of bears during hibernation. Bears are able to use urea to synthesize amino acids and proteins in the plasma (liquid part) of the blood. (The concentration of proteins in plasma should be as constant as possible, otherwise various problems with fluid transport 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 the less you 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 lost to warm it.
If a brown bear's urea concentration has decreased, it becomes lethargic, no longer wants to eat, and falls asleep. But when food is available, the polar bear begins to eat again and raises the urea concentration to normal levels.
It is interesting that during the period of winter sleep, the polar bear somehow manages to lose almost no mass of bones and muscles. Usually in humans and other animals their weight 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 uses almost only fat. It turns out that in some respects polar bears are better adapted to winter sleep.
Strange as it may seem, they actually don’t sleep! In other words, they doze normally, just like in the summer (only in the summer they almost always sleep more).
So in winter they do not sleep, but start hunting again when there is ice.
But the females have nowhere to go; they have to hide in caves.
Because the cubs of the polar bear, like those of other bears, appear small (their weight is less than a kilogram) and blind; they are covered with only a small fluff. Almost always, females make a cave on the shore, sometimes 50 km from the seashore.
Almost always, a bear makes a cave in a snow dune, but if there is not a lot of snow, she can also dig a hole in the frozen ground. The female lies down in the cave precisely at this moment, when the ice melts and hunting becomes quite problematic.
But until she leaves the cave, she will be in a state of winter sleep: she does not eat, does not drink, does not pee or poop.
How does the female manage to accumulate nutrients for long sleep and for raising cubs (and there are almost always two of them)?
But the polar bear actually uses only fat. It turns out that in some respects polar bears are more adapted to winter sleep.
Bears can use urea to synthesize amino acids and proteins in the plasma (watery part) of the blood. (The concentration of proteins in plasma should be as constant as possible; otherwise, various problems arise with metabolism and transport of fluids in the body.) In addition, the lower the urea content, the less it needs to be excreted in the urine, which means the less you need to drink.
Despite the fact that water in the form of snow is almost always simply cheap in the Arctic, drinking (or rather, having) it is energetically unprofitable; quite a lot of energy is wasted on warming it.
If a brown bear's urea concentration has decreased, it becomes lethargic, no longer desires, and falls asleep.
Apparently, this allows the bears to adjust the beginning of the development of the embryos to the time they enter the cave; because this time in almost everything depends on the conditions in a given area and on the weather that year.
But snow white bear in the presence of food, it begins to eat again and raises the urea concentration to normal levels.
Catchy, what a period of winter sleep snow white bear somehow manages to actually not lose any bone mass or muscle. Almost always, in other animals and humans, their mass rapidly decreases during long periods of immobility, even while food is available; The mass of bones and muscles also decreases in other species of bears during sleep.
But in winter they do not fall asleep. (The hibernation of bears is more accurately called winter sleep; bears do not have true hibernation, since their body temperature does not actually drop, and they can wake up at any second.) B winter Only pregnant females and those nursing newborn cubs fall asleep. Other snow-white bears, if they lie in caves, then short term and not every year.
And this is strange because snow white bear a close relative of the brown bear.
They came from common ancestors who lived only 100-50 thousand years ago (for the evolution of species this is not at all that long ago).
It is not very clear why all snow-white bears would not gorge themselves in the same way. But for some reason they don't do this.
Even in nature, these species sometimes interbreed.
At the same time, in terms of their fate, snow-white bears are very different from brown bears.
It’s striking that, apparently, at any time of the year, during a long period of fasting, polar bears seem to sleep on the move.
The concentration of urea in their blood rapidly drops, which is typical for other species of bears during hibernation.
They can no longer hunt seals. On the land most of Arctic animals are able to run away from a snow-white bear and swim away from it into the sea.
Cubs almost always appear in November-January, and remain in the cave until February-March. Before the birth of the cubs, the mother bear actually dozes for the most part, but during the birth she awakens, and after the birth she has to doze less.
It turns out that mating in polar bears occurs in the spring in April-May. Immediately after mating, pregnant females begin to feed so intensely that by dawn they become two hundred kg heavier, and at times their weight actually multiplies!
At the same time, the development of embryos in the female bear’s tummy stops at an early stage in the spring and continues only in the fall; Previously, they will be in a state of rest (this is scientifically called embryonic diapause).
They are hunted by snow-white bears on the ice.
They either snatch the seal with their paw from a hole in the ice through which the seal is breathing, or they lie in wait and grab seals that have climbed out onto the ice to rest. In almost all areas of the Arctic where polar bears live, the ice melts one hundred percent by the end of summer.
Great if you manage to find the carcass of a dead whale or walrus on the shore.
What if no, then in August and autumn the bears are malnourished at times for a couple of months at a time.
The main food of polar bears is seals. These are such seals.