The bear is a formidable forest predator that belongs to the family of mammals, but has the stockiest physique. A special phenomenon is the winter bear hibernation, the causes and features of which we will examine in detail today.
Which bears hibernate?
There is a nomadic spirit in bears, and many species move all year round, with the exception of the brown and Himalayan bear, just these species go to a cozy den for the winter and refuse to wander around the world, preferring a measured sleep to them. The females also sleep polar bear falling asleep while bearing offspring.
Causes of hibernation in bears
The reasons why bears hibernate are as follows:
- Serious difficulties with subsistence in the cold season. It is not difficult for bears to provide themselves with food of animal origin in winter, but such a diet will not be complete and sufficient for their survival. True, the sense of smell of this predator allows him to easily find berries and fruits in snowdrifts, but all the same, these finds are too scarce for wintering. That is why there is no better way out than to plunge into a long and healthy sleep.
- Bear size plays a role in this important biological process. The average weight of a clubfoot is about half a ton. Just imagine how much provisions are needed to keep this hulk fed all winter. There is practically no vegetation, and catching a hare, a fox or a fish on an ice-bound river is not an easy task. And in winter, like in any living organism, energy consumption is much higher than in summer - a lot of energy is spent on maintaining the optimal body temperature in the cold.
Hibernation and its features
In terms of duration, hibernation can stretch up to six months, so you need to stock up on energy for future use. During sleep, the body will extract it from subcutaneous fat, carefully deposited in bear bins in the summer.
During the sleepy period of the year, the body begins to function differently - in scientific literature such a transformation is called a process suspended animation , in which the heart rate slows down and breathing becomes more rare. This mode contributes to the reasonable consumption of the oxygen supply in the bear den and saves the most valuable nutritious subcutaneous fat - these two important resources stretch for months.
Interestingly, during hibernation, a bear can lose weight by almost 2 times.
The animal sleeps quite sensitively - you can confidently say that he just dozes for a long time. Therefore, if a flock of hungry, howling predators rush past the lair, this can easily wake up the bear. As you know, there is nothing worse than waking up a sleepy sleeper, and even more so a bear - he is angry and hungry, so he can go to the nearest village for food to open a couple of warehouses there.
Often female bears do not waste time in winter and give birth to cubs in the den, sometimes up to 5 pieces per litter. The weight of a newborn clubfoot is only a few hundred grams. Bear cubs are born as blind helpless silly babies and their food for the first months is mother's milk. Babies spend up to 1.5 years of their lives with a bear.
Probably everyone knows that stumbling upon a bear with a cub is a dangerous sight, which is even scary to wish for the worst enemy, because when meeting with a bear it can be very bad - the maternal instinct of a bear will make you tear the threat to shreds.
Why suck a paw in hibernation: interesting versions
People say that a bear in hibernation sucks its own paw, they say, thanks to this it is easier for him to survive the harsh Russian cold. True, few people can say for sure what kind of paw they are actually talking about. Yes, and having opened a search engine, finding a photo with this spectacle is almost impossible - the photos come across strange and diverge from expectations, given that today even hunters and foresters have mobile phones with a camera. How then to know the truth?
Version one
Everything is extremely simple:
- Scientists say that the bear's paw is covered with a thick layer of skin, thanks to which they easily overcome rocky ledges without experiencing discomfort.
- During hibernation, new skin grows, preparing the paws for the new summer season.
- To make the process faster, the bear places its paw closer to the muzzle and bites off unnecessary skin. This process is unpleasant, because the sole itches during molting.
Version two
The second interesting hypothesis is related to bear cubs, which can suck their paws, not living in the wild. This is due to the fact that the baby in nature, as we have already said, feeds on mother's milk for a long time, and the bear's nipples are not on the stomach - but in the armpits and in the groin. If a little bear grows up in fatherlessness and without a mother, then he is fed with a pacifier, like a child. But instincts take their toll: the bear cub is sorely lacking contact with its mother, so it begins to suck on its paw, considering it to be the mother's nipple. By the way, in nature, such a phenomenon occurs infrequently.
Bear after hibernation: what is it like?
In the video below, you can see unique footage captured by random eyewitnesses, in which the bear just got out of the den after a long hibernation - its hair does not shine, but hangs in tatters, and nothing is left of its impressive size, the bear is still sleepy and a little confused . As soon as the bear eats the first berries, digs up someone's food supplies in last year's grass and catches fish hurrying along the stormy rivers to spawn, it will very soon regain its impressive size.
Nature is ingenious and prudent, proof of which is the hibernation of bears. Thanks to this phenomenon, they successfully survive the winter, consuming the fat that they have accumulated for this period.
Many mysteries are kept in nature, many still unsolved and inexplicable in it. And yet, with the passage of time, as a result of observations and experiments, mankind managed to give an answer to some of them.
For example, why does a bear sleep in winter and do all species of these animals hibernate? How, under conditions of absolute starvation, does an animal manage to preserve the vital activity of the organism at the same level and continue to actively hunt after a long starvation? Why do brown bears fall into winter sleep, while their polar relatives do not? This article will answer these and other questions.
Why does a bear sleep in winter
As you know, brown bears are fairly large animals. Therefore, in order to feed themselves, they need a decent amount of food. And although they are omnivorous, in the winter the plant part of the diet disappears, and it is quite difficult to survive only by eating other living creatures - birds, small mammals, eggs, carrion, insects, fish. Yes, and it is impossible to find frogs, ants, slugs in winter, and hunting for hares and wild boars is problematic, because they simply run away from the clubfoot, which falls into the snow under its own weight and is not able to move quickly.
Note: It is because of the inability to fully eat these predators hibernate. Hibernation is understood as a period of slowing down of vital processes during the inaccessibility of food, when the animal cannot maintain activity and the previous level of metabolism.
The characteristic signs of hibernation are called: a decrease in body temperature, a slowdown in the functioning of the respiratory system and the heart, and inhibition of nervous activity. So, during winter sleep, the body temperature of a brown bear drops from 37-38 to 31-34 degrees, and its metabolic processes slow down. However, this dream is not very strong, because at the slightest danger the animal wakes up and can leave the den (Figure 1).
Figure 1. As winter approaches, bears become lethargic and begin to prepare for hibernation. Hibernation is preceded by the appearance of lethargy, slowness of movements, and a decrease in the animal's appetite. In this state, the animal does not defecate and does not urinate, because all waste products are processed into proteins necessary to maintain vital processes. The duration of winter sleep can be from 2.5 to 6 months, depending on weather conditions and the amount of nutrients accumulated by the animal.
Hibernation ends in spring with the appearance of the first grass. At the same time, bears leave their shelters at different times: adult males leave first, then juveniles. Females with cubs leave their dens last - in April-May. This is due to the fact that the female brings offspring in January-February, therefore, with the advent of spring, the cubs are still too small to release them into an external environment full of dangers. Already at the beginning of autumn, animals begin to eat intensively, picking up berries and fruits, eating insects and oats. In this way, they accumulate subcutaneous fat, which is so necessary for them for hibernation, and in females - also for feeding babies.
Features of hibernation of bears in winter
The food consumed by animals is the source of energy through which they exist. Therefore, the more active the lifestyle, the more energy the body needs, the more food should be consumed. Therefore, with an insufficient amount of food, it becomes necessary to reduce the intensity of all metabolic processes, which can be achieved by being at rest (Figure 2).
Note: It is for this reason that bears fall into winter sleep when plant foods, which make up 80% of their diet, disappear.
However, even during hibernation, the animal can wake up in case of danger and show sufficient activity. This is due to the fact that energy expenditure during winter sleep is minimal, and the cells receive it exactly as much as is necessary to maintain the vital activity of the body. The reserves of fat and glycogen accumulated during the active period of the year are consumed gradually, so they are enough until the onset of spring. Conversely, an animal that does not store enough fat is much less likely to oversleep until spring. A hungry animal leaves the den ahead of time and wanders in search of food, remaining aggressive and dangerous to humans. The connecting rod bear may attack dogs or livestock, search for food in landfills, or beg people on highways.
Figure 2. During hibernation, all life processes slow down In addition to fat and glycogen, oxygen is another source of energy. During winter sleep, the body is inactive, its tissues need a small amount of oxygen and nutrients, so the blood that carries them moves much more slowly, the heart rate decreases, the respiratory rate decreases significantly, respectively, energy costs are reduced. And although after hibernation the animal can lose up to half of its own body weight, it still finds the strength to leave the den and begin active life even after a 3-month hunger strike.
By observing animals in a den, scientists were able to find out that predators do not suck their paws, as is commonly believed, but lick them to relieve itching, which occurs as a result of a change in the skin on the pads of the limbs. Thus, falling into hibernation is a genetically incorporated defense mechanism that allows the bear's body to adapt to a lack of nutritional resources.
How a bear sleeps in a den in winter
In a warm and safe den, a bear can sleep through the whole winter. Most often, the animal is located on its side, curled up in a ball, sometimes - on its back, less often - in a sitting position, lowering its head between its paws. Males and young sexually mature individuals sleep alone, and females, who have cubs of the year, fit together with them (Figure 3).
Note: Unlike other animals that become numb during hibernation and show no signs of life, the body temperature drops slightly, by only 3-5 degrees, their heart beats rhythmically, although it slows down, and breathing becomes somewhat less frequent. Therefore, the animal easily wakes up from winter sleep in case of alarm, and often leaves the den itself during prolonged thaws, returning to it with a noticeable cold snap.
If the temperature in the den becomes very low, the dormant animal wakes up, burrows deeper and falls asleep again. During winter sleep, the animal's body does not remove waste products, but reprocesses them into useful proteins and water.
Figure 3. Types and arrangement of the lair It took more than one thousand years natural selection to form such a complex system of animal adaptations to harsh climatic conditions. The hibernation of a brown bear usually lasts about four months (from the second half of November to the first half of April), which depends on weather conditions, the age and health of the animal.
Why polar bears don't sleep in winter
Brown and polar bears, descended from common ancestors only 150 thousand years ago, and often interbreeding in wild nature, strikingly different habits and way of life. So, a brown bear in the cold season falls into a state of winter sleep, but his white counterpart hardly sleeps in winter. He dozes more sensitively and for a short time, usually in the spring-winter period. The only exceptions are pregnant or nursing females.
Figure 4. Polar bears are very different from their brown relatives. The peculiarities of this behavior are explained by the fact that the diet of the polar bear consists mainly of seal meat and fish, which are available almost all year round, even during the winter cold, when he has the opportunity to hunt them on hard ice. Predators snatch seals from the holes through which they breathe, or grab seals on the ice while resting. By the end of summer, when the ice is almost completely melted, it becomes more difficult for the bear to hunt, as prey easily swims away from him or runs away on land. Then the animal has to be content with the carcasses of dead whales or walruses found on the shore, and sometimes even starve.
Note: During such periods of temporary starvation, the animals seem to "sleep on the go." In other words, their body has all the signs of hibernation. So, the concentration of urea in their blood drops sharply, which causes lethargy, drowsiness and loss of appetite in a brown bear.
The polar bear does not hibernate, and in the presence of food it is able to raise the concentration of urea to a normal level:
- The body of a white bear uses urea for the synthesis of amino acids and blood plasma proteins, which ensure the maintenance of the necessary level of metabolism in the body.
- The lower the urea content, the less often it needs to be removed, which means that the need to quench thirst is also reduced, which is energetically justified in conditions of lack of food, because in order to get water from snow in the Arctic, you need a lot of energy to warm it. Therefore, as soon as the ice appears, the polar bear goes hunting, because the well-being of the animal in the coming year depends on it.
- Females nursing babies have to spend the winter in a den. This is due to the fact that the cubs of the white subspecies are born very small, blind and helpless. Their body is not covered with wool, but with a short fluff, which is unable to protect the animal from the northern cold.
- Polar bears build dens on the shore, in snowdrifts, and in case of insufficient snow, even in a hole dug in frozen ground.
- Usually females lie in the den when hunting becomes problematic due to the melting of ice.
Until the birth of babies, they mostly sleep. Cubs (usually two) are born, as a rule, in November-January and remain in the den until spring. The female, who is with them, is in a state of winter sleep, that is, she does not eat, drink, or defecate, while feeding her offspring with milk (Figure 4). All these processes are possible due to the fact that immediately after mating, which occurs in April-May, pregnant females begin to eat heavily in order to accumulate the necessary supply of nutrients. Often, female bears manage to increase their body weight by 200 kilograms, while the development of the embryos is suspended for early stage and resumes only in autumn, closer to the time the female enters the den, which depends on several factors, for example, weather conditions or the rate of accumulation of nutrients by the animal. It is also interesting that during the period of winter sleep, the bear manages not only to feed the babies, but also not to lose bone and muscle mass, because only body fat is consumed during hibernation. From all of the above, it turns out that it is polar bears that are most adapted to winter sleep.
In the video you can see what a bear's hibernation den looks like.
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). The brown bear perfectly hibernates in the winter, and can the polar bear sleep in the den in the summer?
And in general, do polar bears have dens?
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 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.
sources
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 hibernate. 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 pregnant females, who hibernate for several months until they have babies. After the birth of the cubs, the 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 a lair in winter. Bears choose very secluded places in woodland 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.
There used to be a lot of brown bears in nature. Families and groups were distinguished among them. Now they have left only the division on the basis of geographical location. Many people have an idea why the bear hibernates. But it makes sense to figure out if all the "clubfoot" are prone to this? Perhaps in the southern regions there are animals that are awake all year round?
Distinctive features
The brown bear is a large animal. Individuals living in the European part of the continent reach 1.4 - 2 m with a weight of up to 400 kg. Bears of Kamchatka and Alaska can weigh up to 1000 kg. Such a giant, standing on its hind legs, has a height of up to 3 m.
The body of a brown bear is powerful. The head is massive, with small eyes and ears, high withers, thick fur, wide set and short tail - the typical appearance of a brown (up to 10 cm long) does not hide on powerful five-fingered paws.
Bears are plantigrade animals. If necessary, for a short time they develop speeds up to 40-50 km / h. Water obstacles are overcome with ease. It will not work to hide on a tree from an angry bear.
Their diet is dominated by plant foods (by ¾). First of all, these are berries, acorns, nuts, roots and tubers of plants, as well as their succulent stems. It is this feature that is decisive in understanding why the bear hibernates in a harsh time. As for the color, the main color is brown. The shade of wool can differ significantly even in individuals living in the same territory (from black, fawn-gray and gray to reddish-brown).
Lifestyle
Bears define their territory and fix the boundaries with marks. It is believed that they live settled, although they may make migrations associated with the search for more suitable feeding places. In early spring they are looking for clearings where the snow melts and the ground thaws faster. During the period of midge activity, they can leave the thicket to open places. During spawning, they make trips to rivers to hunt for fish in shallow water.
But they cannot move to the southern regions during the winter - this is another good reason in understanding why bears hibernate in winter. They lead and are forced to return to their traditional habitats. With the advent of autumn, food is becoming more difficult to find - you have to look for a way to wait out the cold.
The ability to fall asleep in the cold is also characteristic of other animals. By the way, not only the winter period causes hibernation. In the desert area, small rodents can enter a sleepy state in the summer, during a period of drought. Under adverse conditions, unplanned hibernation can last until spring.
A brown bear cannot afford such a long rest. The period of his hibernation can vary from 2.5 to 6 months. But sometimes it lasts longer if circumstances so require. When asked why Brown bear falls into hibernation, and does not harvest stocks of roots, nuts and acorns for the winter, it is difficult to answer. Apparently, he prefers to store them in the form of subcutaneous fat - it is more reliable and warmer.
It should be clearly understood why the bear hibernates. This is caused by the only way animals can survive the winter. At the same time, it should be noted that individuals living in the southern regions with a sufficient food supply can do without seasonal sleep all year round.
It is also worth dispelling the myth about the alleged ability of bears to suck their paw and thus eat in winter. This habit, according to experts, is associated with the peculiarity of the molting of the soles of bears. climbs off them during their stay in the den. This is due to lack of movement and load. Young and delicate skin on the soles freezes. Therefore, the bears warm it with their breath and lick it with a warm tongue.
Rods: why the bear hibernates in winter
What happens if you wake up an animal in a lair? Hibernation of bears is superficial. A disturbed animal will wake up and be able to quickly respond to danger or a sudden change in conditions. As a rule, an awakened bear will look for a new lair if the old one is not suitable for sleeping.
In that case, why does the brown bear hibernate again in winter, and not wait for spring? This is the easiest way to survive. But there are situations when, for various reasons, animals do not gain enough fat over the summer. They cannot lie in a den in this state until spring. Hunger makes them leave the lair and go in search of food. Roots, nuts, acorns and other edible things cannot be found under the snow. The only way to survive is to engage in predation.
Under such circumstances, the bear decides to attack weakened animals and even predators. He is ready to take prey from wolves and foxes, eat carrion. He can enter the surrounding settlements, destroy apiaries, attack livestock and people. A meeting of a person with a starving rod bear can end sadly - this must be remembered and understood.
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