A bird that goes to sleep. Causes of imaginary death (anabiosis) in plant and animal organisms, allowing them to survive adverse winter conditions. Do birds hibernate

16.03.2020

On the verge of life Denkov Veselin A.

Are there birds that hibernate in winter?

So, we found out that most animals with unstable body temperature, which depends on environment fall into a state of hibernation. But surprisingly, many animals with a constant body temperature, such as birds, can also hibernate during the unfavorable seasons of the year. It is known that most birds avoid adverse winter conditions by migrating. But even Aristotle (384–322 BC), in his multi-volume History of Animals, drew attention to the fact that “some birds fly away to spend the winter in warm countries, while others take refuge in various shelters, where they fall into hibernation."

The great Swedish naturalist Carl Linnaeus came to this conclusion, who in his work The System of Nature (1735) wrote: “In autumn, when the cold starts, swallows, not finding enough insects for food, begin to seek shelter for wintering in reed beds. along the banks of lakes and rivers.

For a long time, the statements of Aristotle and Linnaeus were rejected by ornithologists, who referred to the well-known fact that some birds migrate to warm countries, while non-migratory ones are active in winter, and science does not know the birds that hibernate, contrary to the assertion of many. Only after American scientists discovered in 1937 a hibernating nightjar (Phalaenoptilus nuttalii) in a rock crevice did it become clear that some species of birds can fall into a similar state during unfavorable seasons of the year. Both scientists conducted more in-depth studies and found that before falling into hibernation, this bird species loses a significant part of its weight, and at a certain point, as a result of this exhaustion, the mechanism of transition to a state of torpor is activated. In this state, the metabolism drops sharply, the need for oxygen is reduced by almost 30 times, and the body temperature drops from 40-41 ° C to 18-19 ° C and even lower. The birds fell into a torpor that lasted about 3 months and gave the impression that they were dead. It was found that during hibernation, a nightjar weighing 40 g consumed 0.15 ml of oxygen per 1 g of weight per hour, while in the normal state - 2.7 ml. The same scientists ringed one of these birds, and in subsequent years it turned out that she always hibernated in the same place for 4 years.

Later it was found that another of its relatives, the small nightjar (Chordeilis minor), also living in North America and the Antilles, falls into a state of hibernation. In Denmark, a European nightjar (Caprimutgus europeus) was found in the same condition at an air temperature of 0 °C. Experiments carried out with him showed that when the air temperature was artificially lowered to 4 ° C, the bird fell into a stupor, and its body temperature dropped from 37-40 ° C to 16-17 ° C, and the respiratory rate - from 50-70 to several minute. There are observations that some species of swallows (village and rocky) also hibernate in winter.

A state of short-term torpidity, which scientists call torpidity, has been observed in newly hatched chicks of the black swift (Apus apus), which fall into this state when the parents leave them for several days under adverse conditions (for example, during an approaching cyclone). In a state of torpor, the body temperature of these chicks dropped from 39 °C to 20 °C and even lower, pulse and respiration slowed down, and in this state they survived for 7–12 days. Having appeared again, the parents warmed them with their bodies, and the chicks returned to life. In favorable times of the year, young swifts flew out of the nest after 33–35 days, and in unfavorable times, when they fell into a state of stupor, they needed 40–50 days.

It has long been known that chicks of some hummingbird species also fall into a similar torpid state if the mother, having flown away for food, lingers for more than ten minutes (in hummingbirds, only females feed offspring). After her return, warmed by maternal warmth, they return to life. It has been established that adult hummingbirds of several species (Calypte costae, C. anna, Eugenes Lampornis), living on the American continent, are also able to fall into a state of torpor on especially cold nights, when their body temperature drops to 8.8 °C.

It has been proven that the weight of various species of hummingbirds ranges from 1.7 to 19.1 g, and the oxygen demand of small specimens at rest is 11–16 ml per 1 g of weight per hour, during flight - 70–85 ml, and in a state of stupor only 0.17 ml. The energy expenditure of hummingbirds is high, and there is a danger that hummingbirds with a body temperature of 44 ° C will not be able to endure the period when they sleep without food, as they will not have enough energy reserves. In this situation, their body, with excessive cooling from exhaustion at night, will lose the opportunity to warm up again at the beginning of its active phase. Meanwhile, as you know, the nights on the South and Central American high plateaus, where hummingbirds live, are cold. That is why hummingbirds have a protective mechanism - they fall into a torpid state at night, and their body temperature is compared with the ambient temperature; thus, they do not give up their heat and store energy that is not used to generate heat in the body. In this case, the law of the Dutch physiologist Van Gough applies, reflecting the relationship between the reaction rate of chemical processes and temperature (if the body temperature drops by 10 ° C, the metabolic processes will begin to proceed almost 3 times slower). So if the body temperature of a hummingbird drops from 44°C to 34°C, this will lead to a threefold reduction in metabolism and, accordingly, to a significant conservation of energy.

A similar regulation of body temperature during stupor was also found in the purple hummingbird (Eulampis jugularis), which, like other hummingbirds, easily falls into a torpid state. In a state of torpor, the body temperature of this species of hummingbird is usually close to air temperature, but if the latter falls below 18 ° C, the body temperature of the bird no longer drops and remains at 18–20 ° C.

The torpor into which some species of birds fall is quite different from the hibernation common to many mammals. First of all, the body of birds not only does not accumulate energy reserves in the form of fat, but, on the contrary, consumes a significant part of them. While mammals go into hibernation, having noticeably gained weight, birds lose a lot of weight before stupor. That is why the phenomenon of torpor in birds, according to the Soviet biologist R. Potapov, should be called not hibernation, but hypothermia.

Until now, the mechanism of hypothermia in birds is not fully understood.

It is interesting that all birds capable of falling into a state of stupor are systematically close relatives among themselves and have common physiological and ecological features. The fall of these birds into a state of stupor under adverse living conditions is an adaptive physiological reaction that has been fixed in the process of evolution.

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Many animals spend the winter in a state called hibernation. However, of the several thousand species of birds known today, only one - the California nightjar - plunges into hibernation.

This bird is active mainly at night, and during the cold winter months it hides in cracks between stones and other hiding places. Its normal body temperature is 35-45.5°C, but during hibernation it drops to 20°C and lower if it gets cold. So the bird saves energy obtained from fat stores.

Previously, scientists did not suspect that the nightjar hibernates. Only in 1946, a sleeping bird was discovered in one of the California canyons. However, the Indians probably knew about this, because they called this bird "dormouse."

In deep sleep

Nightjar hibernates in secluded places like cracks between stones. Every year he spends about 90 days without movement, with his eyes closed.

When threatened with an attack, the nightjar inflates its body and spreads its wings. Nightjar is a nocturnal bird that feeds on insects. She spends the day in bushes or trees.

Nightjar - a bird that hibernates

Even the father of science, Aristotle, in his famous History of Animals, wrote that some birds fly away for the winter to warm countries (more about), but some don’t fly away, but hide in secluded shelters and burrows, where they hibernate. This opinion was held in science until the beginning of the 19th century. And, even such prominent naturalists as Carl Linnaeus and Georges Cuvier once wrote that swallows become numb for the winter, spending this unfavorable time at the bottom of the marshes. Is it true? Do birds hibernate? We invite you to find out the answer to this question from our publication ...

Do birds hibernate

When biology had sufficiently studied the flights of birds, the assumption of hibernation of birds was completely abandoned and was sometimes cited in textbooks as a curiosity of distant antiquity. However, most recently, reports of strange phenomena in migratory swifts and swallows have begun to reappear in the scientific literature. First in one secluded place, then in another, they found a large concentration of petrified birds, which, however, came to life and flew away as soon as they were taken in hand. Such cases were observed, as a rule, during autumn or spring flights in cold, cloudy weather. In connection with such reports, old assumptions about the ability of birds to hibernate came to life.

This question has not yet been fully investigated, but at least one species of birds is already known that hibernate for the whole winter. This bird is a small North American nightjar native to the western United States.

Nightjar hibernation example

In the winter of 1947, one of the naturalists stumbled upon a nightjar in one of the gorges, which was in a state of stupor. In subsequent years, zoologists studied in detail the hibernation of this little nightjar and found out many curious details. So, the bird feeds mainly on nocturnal insects, which become less and less as winter approaches (find out). Birds begin to lose weight, and, apparently, at some specific moment of exhaustion in the body, they turn on the mechanism of transition to a state of stupor. It takes place in November. Nightjars choose secluded niches or cracks in rocks - usually on the sunny side - and sink into a torpor that can last up to 85 days. At this time, the level of metabolism in birds in the body is sharply reduced.

Oxygen consumption, in particular, is reduced by a factor of 30. And, body temperature can drop to 4.8 degrees.

The bird looks like it's dead. The stupor ends in the month of March, when it becomes warm enough. Feathered wakes up quickly, and normal body temperature is restored in a few hours. It should really be borne in mind that in those places where this nightjar winters, the winter is very mild and even in January the air temperature during the day sometimes rises to +23 degrees above zero.

Features of hibernation nightjars

The torpor into which the nightjar falls is very different from the hibernation into which many mammals fall. First of all, the bird's body not only does not accumulate energy reserves in the form of fat, but, on the contrary, consumes a significant part of them. If ground squirrels or marmots go into hibernation, literally swollen with fat, then the birds become very thin before becoming numb. Their reserves of energy resources are running low and only enough to wake up and resume food production. Therefore, the phenomenon of bird torpor is not called hibernation, but hypothermia.

Sections: Biology

Goals: increase the areas of knowledge of students; learn to analyze the phenomenon of temporary cessation of vital activity in living organisms, using it as a means to adapt and survive in adverse conditions.

Equipment: tables of molluscs, crustaceans, insects, fish, amphibians, reptiles, birds, mammals.

The winter season is unfavorable for many representatives of the animal and plant world, both due to low temperatures and a sharp decrease in the ability to get food. In the course of evolutionary development, many species of animals and plants have acquired peculiar adaptive mechanisms in order to survive in an unfavorable season. In some species of animals, the instinct to create food reserves has arisen and established itself; others have developed another adaptation - migration. Strikingly long flights of many species of birds, migration of some species of fish and other representatives of the animal world are known. However, in the process of evolution in many species of animals, another perfect physiological mechanism of adaptation was also noticed - the ability to fall into a lifeless state at first glance, which in different species of animals manifests itself in different ways and has different names (anabiosis, hypothermia, etc.). Meanwhile, all these conditions are characterized by inhibition of the body's vital functions to the minimum that allows it to survive adverse winter conditions without eating. Such a state of imaginary death falls into those species of animals that are not able to provide themselves with food in winter and for them there is a danger of death from cold and hunger. And all this, developed in the process of evolution, is subject to strict natural expediency - the need to preserve the species.

Hibernation is a widespread phenomenon in nature, despite the fact that its manifestations are different in representatives of certain groups of animals, whether they are animals with unstable body temperature (poikilothermic), also called cold-blooded, in which the body temperature depends on the ambient temperature, or animals with a constant body temperature (homeothermic), also called warm-blooded.

From among animals with unstable body temperature, various types of mollusks, crustaceans, arachnids, insects, fish, amphibians and reptiles fall into a state of hibernation, and from animals with a constant body temperature, several species of birds and many species of mammals.

How do snails hibernate?

From the soft-bodied type, many types of snails fall into hibernation (for example, all land snails). Encountered garden snails hibernate in October, and it lasts until early April. After a long preparatory period, during which they accumulate the necessary nutrients in their bodies, the snails find or dig minks so that several individuals can winter together deep underground, where the temperature will be maintained at 7 - 8 ° C. Having clogged the minks well, the snails descend to the bottom and lie with the shell opening up. They then close this hole, releasing a slimy substance that soon hardens and becomes elastic (film-like). With a significant cold snap and a lack of nutrients in the body, the snails burrow even deeper into the ground and form another film, thus creating air chambers that play the role of an excellent insulator. It has been established that during a long wintering period, snails lose more than 20% of their weight, with the largest loss occurring in the first 25-30 days. This is due to the fact that all metabolic processes gradually fade in order to reach the minimum at which the animal falls almost into a state of suspended animation with barely perceptible vital functions. During hibernation, the snail does not feed, breathing almost stops. In the spring, when the first warm days come and the soil temperature reaches 8-10 ° C, when vegetation begins to develop and the first rains fall, the snails come out of their winter shelters. Then begins intensive activity to restore exhausted food reserves in their body; this is expressed in the absorption of a huge amount of food compared to their body.

Water snails, pond snails, also fall into a state of hibernation - most of them burrow into the silt at the bottom of the reservoir in which they live.

Where do crayfish hibernate?

Everyone knows the threat popular among the people: "I'll show you where the crayfish hibernate!". It is believed that this proverb appeared during the time of serfdom, when the landlords, punishing the guilty serfs, forced them to catch crayfish in the winter. Meanwhile, it is known that this is almost impossible, since crayfish overwinter, deeply buried in holes at the bottom of reservoirs.

From the point of view of taxonomy, the class of crustaceans is divided into two subclasses - higher and lower crustaceans.

Of the higher crustaceans, river, marsh and lake crayfish fall into a state of hibernation. Males hibernate in groups in deep pits at the bottom, and females alone in minks, and in November they glue fertilized eggs to their short legs, from which ant-sized crustaceans hatch only in June.

Of the lower crustaceans, water fleas (genus Daphnia) are of interest. They lay, depending on the conditions, two types of eggs - summer and winter. Winter eggs have a strong shell and are formed when unfavorable living conditions occur. For some species of lower crustaceans, drying out and even freezing of eggs are necessary condition to continue their development.

Diapause in insects

By the number of species, insects surpass all other classes. Their body temperature depends on the environment, which has a strong effect on the speed of vital influences, and low temperatures greatly reduce this speed. At negative temperatures, the entire development of the insect slows down or practically stops. This anabiotic state, known as "diapause", is a reversible stoppage of developmental processes and is caused by external factors. Diapause occurs when unfavorable conditions for life arise and lasts all winter, until conditions become more favorable with the onset of spring.

The onset of the winter season finds different types of insects at different stages of their development, in which they hibernate - in the form of eggs, larvae, pupae or adult forms, but usually each individual species falls into diapause at a certain stage of its development. So, for example, the seven-spotted ladybug hibernates as an adult.

It is characteristic that the wintering of insects is preceded by a certain physiological preparation of their body, consisting of the accumulation of free glycerol in their tissues, which does not allow freezing. This occurs at the stage of development of the insect in which they will overwinter.

Even with the onset of the first signs of cooling in autumn, insects find comfortable shelters (under stones, under the bark of trees, under fallen leaves in burrows in the soil, etc.), where after a snowfall the temperature is moderately low and uniform.

The duration of diapause in insects is directly related to the reserves of fat in the body. The bees do not fall into a long diapause, but still at a temperature of 0 to 6 ° C they become numb and can stay in this state for 7-8 days. At lower temperatures they die.

It is also interesting how insects accurately determine the moment when they should exit the anabiotic state. Scientist N.I. Kalabukhov investigated anabiosis in some species of butterflies. He found that the duration of diapause varies from species to species. For example, the peacock butterfly was in a state of suspended animation for 166 days at a temperature of 5.9 ° C, while the silkworm needed 193 days at a temperature of 8.6 ° C. According to the scientist, even differences in the geographical area affect the duration of diapause.

Do fish hibernate?

In a peculiar way, some species of a large class of fish adapt to low water temperatures in winter. Normal body temperature in fish is not constant and corresponds to the temperature of the water. With a sudden sharp drop in water temperature, the fish fall into a state of shock. It is enough, however, that the water warms up, and they quickly “come to life”. Experiments have shown that frozen fish come to life only when their blood vessels are not frozen.

Originally adapted to low water temperatures in winter, some fish that live in Arctic waters: they change their blood composition. With a decrease in water temperature in autumn, salts accumulate in their blood in such a concentration that is characteristic of sea water, and at the same time the blood freezes with great difficulty (a kind of antifreeze).

From freshwater fish, carp, ruff, perch, catfish and others fall into hibernation in November. When the water temperature drops below 8 - 10°C, these fish move to the deeper parts of the reservoirs, burrow large groups in the silt and remain there in a state of hibernation throughout the winter.

Some marine fish also endure extreme cold while hibernating. So, for example, herring already in autumn approach the coast of the Arctic Ocean in order to fall into a state of hibernation at the bottom of some small bay. The Black Sea anchovy also winters in the southern regions of the sea - off the coast of Georgia, at this time it is not active and does not consume food. And the Azov anchovy before the onset of the winter period migrates to the Black Sea, where it gathers in groups in a relatively sedentary state.

Hibernation in fish is characterized by their extremely limited activity, complete cessation of feeding, and a sharp decrease in metabolism. At this time, their body is supported by the reserves of nutrients accumulated due to abundant nutrition in the autumn.

hibernation of amphibians

In terms of lifestyle and structure, the class of amphibians is transitional between typically aquatic vertebrates and typically terrestrial animals. It is known that different kinds frogs, newts, salamanders also spend the unfavorable winter season in a state of stupor, as these are animals with unstable body temperature, which depends on the ambient temperature.

It has been established that the hibernation of frogs lasts from 130 to 230 days and its duration depends on the duration of winter.

In reservoirs, in order to overwinter, frogs gather in groups of 10-20 specimens, burrow into silt, into underwater depressions and other voids. During hibernation, frogs breathe only through their skin.

In winter, newts usually nestle under warm, rotten stumps and trunks of fallen trees. If they do not find such convenient "apartments" nearby, they are satisfied with cracks in the soil.

Reptiles hibernate too

From the class of reptiles, almost all species of our fauna fall into a state of hibernation in winter. Low winter temperatures are the main reason for this phenomenon.

Winter quarters are usually underground caverns or voids formed around large old stumps with rotten roots, crevices in rocks, and other places that are not accessible to their enemies. In such shelters, a large number of snakes gather, forming huge coils of snakes. It has been established that the temperature of snakes during hibernation almost does not differ from the ambient temperature.

Most species of lizards (meadow, striped, green, forest, spindle) also hibernate, burrowing into the soil, into burrows that are not threatened by flooding. On warm, sunny days in winter, lizards may “awake” and crawl out of their winter shelters for several hours to hunt, after which they again hide in their burrows, falling into a state of torpor.

Bog turtles spend the winter burrowing into the silt of the reservoirs in which they live, while terrestrial turtles climb to a depth of 0.5 m into the soil into some natural shelters or holes of moles, foxes, rodents, covering themselves with peat, moss and wet leaves.

Preparation for wintering begins in October, when turtles accumulate fat. In the spring, with temporary warming, they wake up, sometimes for a whole week.

Are there birds that hibernate in winter?

Most animals with unstable body temperature, which depends on the environment, fall into a state of hibernation. But surprisingly, many animals with a constant body temperature, such as birds, can also hibernate during the unfavorable seasons of the year. It is known that most birds avoid adverse winter conditions by migrating. Even Aristotle, in his multi-volume History of Animals, drew attention to the fact that “some of the birds fly away to spend the winter in warm countries, while others take refuge in various shelters, where they fall into hibernation.”

The great Swedish naturalist Karl Linnaeus also came to this conclusion, who in his work “The System of Nature” wrote: “In autumn, when the cold starts, swallows, not finding enough insects for food, begin to seek shelter for wintering in reed beds along the banks of lakes and rivers. ".

Until now, the mechanism of hypothermia in birds is not fully understood. The fall of birds into a state of stupor under adverse living conditions is an adaptive physiological reaction that has been fixed in the process of evolution.

What mammals hibernate in winter?

As in the animals discussed earlier, so in mammals, hibernation is a biological adaptation to survive the unfavorable season of the year. Although animals with a constant body temperature usually tolerate cold climates, the lack of suitable food in winter has caused some of them to acquire and gradually consolidate in the course of evolution this peculiar instinct - to spend an unfavorable winter season in an inactive state of hibernation.

There are three types of hibernation according to the degree of torpor:

1) slight torpor, which easily stops (raccoons, badgers, bears, raccoon dogs);

2) complete stupor, accompanied by periodic awakenings only on warmer winter days (hamsters, chipmunks, bats);

3) real incessant hibernation, which is a stable, prolonged stupor (ground squirrels, hedgehogs, marmots, jerboas).

Winter hibernation of mammals is preceded by a certain physiological preparation of the organism. It consists primarily in the accumulation of fat reserves, mainly under the skin. In some winter sleepers, subcutaneous fat reaches 25% of the total body weight. For example, ground squirrels get fat at the beginning of autumn, increasing their body weight three times compared to spring-summer weight. Before hibernation, hedgehogs and brown bears, as well as all bats, get significantly fatter.

Other mammals, such as hamsters and chipmunks, do not accumulate large stores of fat, but store food in their shelter to use during their brief periods of awakening in winter.

During hibernation, all species of mammals lie motionless in their burrows, curled up into a ball. So it is best to keep warm and limit heat exchange with the environment. Zimnik apartments of many mammals are natural emptiness of stems and tree hollows.

From insectivorous mammals, the hedgehog, preparing for hibernation, collects moss, leaves, hay in a secluded place and arranges a nest for itself. But it “settles” in its new home only when the temperature is kept below 10 ° C for a long time. Before that, the hedgehog eats plentifully in order to accumulate energy in the form of fat.

Winter hibernation of brown bears is a slight stupor. In nature, in summer, a bear accumulates a thick layer of subcutaneous fat and, immediately before the onset of winter, settles in its lair for hibernation. Usually the lair is covered with snow, so it is much warmer inside than outside. During hibernation, the accumulated fat reserves are used by the bear's body as a source of nutrients, and also protect the animal from freezing.

From a physiological point of view, the hibernation of mammals is characterized by the weakening of all vital functions of the body to the minimum that would allow them to survive adverse winter conditions without food.