Hibernation

As winter sleep or hibernation is called a sleep-like state in which certain endothermic or homoiotherme Animals - expire while reducing their body temperature during the cold season - some mammals and few birds, such as the American winter night swallow. Some hibernators like bats, dormice and hazel mice would die if they were forcibly deprived of sleep. Badgers and hamsters can survive without the hibernation phase.

The true hibernators turns - in simplified terms - in the fall of a warm-blooded animal in an alternating hot animal by its body temperature drops to near ambient temperature. During this time, breathing and heartbeat slow down. The energy that is necessary to maintain the vital functions of the winter sleeper during seasonal sleep phase comes from the eroded during the summer fat deposits.

Some mammals (such as bats) hold an interrupted hibernation, others (such as the dormouse, hazel dormouse, hedgehog or groundhog ) a prolonged hibernation with a few brief interruptions. Other animals, such as snails, for example, hold summer sleep due to the heat and lack of water.

The temporal organization of hibernation deals chronobiology.

The behavior of hibernating during the cold seasons

Hibernating in the Fall locations, where they are protected from the intense cold ( hollow tree trunks, caves and the like) and upholster them with hay, straw, leaves, hair, wool and other materials. In the so- decked shelter they usually spend more animals with a contracted, abgekugeltem body and closed eyelids the winter in an energetic saving state, the so-called torpor. Your normal body temperature usually drops it to values ​​9-1 ° C. All body functions are greatly reduced in this state. The breathing is weak, slowing the heartbeat and sensitivity to external stimuli low. Marmots reduce, for example, during hibernation their body temperature from 39 to up to 7 ° C from. Your heart beats a hundred times instead of just two to three times per minute. The pauses in breathing can be up to an hour. Secretion products of the intestinal tract and the liver accumulate in hibernating animals in the lower part of the intestine and are excreted immediately after awakening. Food is not taken during the time of sleep, more than in the occasional awakenings. The animals live off their fat reserves instead of what they have eaten in the fall. With frequent awakening, however, a disproportionate amount of body fat can be consumed so that the reserves are not enough to spring break-in, what the chances of survival decreases. Decrease marmots during hibernation even stomach and intestines by half, liver and kidney by about 30 percent. A special brown adipose tissue, which lies in the shoulder and neck area of hibernators also serves the energy recovery, especially if the animals at elevated ambient temperatures wake up from their hibernation, which takes several hours. In the late phase of waking up the body is brought mainly by muscle tremors back to normal temperature. The warmer it gets, the faster the animals breathe.

The duration of hibernation

The length of hibernation varies with the individual hibernating. When hedgehogs are three to four months; Dormice spend six to seven months in hibernation ( hence its German name). However, it should not be subject to the false notion that there is a several months duration sleep without pause when hibernation. Rather, the sleep runs mostly in sections, with long periods of quiet with greatly reduced metabolism alternating with brief awakenings. Too often the animals during the winter, however, may not wake up because each interim recovery phase to the energy reserves consumed, so that the fat depots were depleted too early and would no longer be for the actual wake-up available in the spring.

Scientists have held longer for an experiment specially fattened dormice than a year in hibernation.

Social hibernation

Some hibernators such as marmots even hold a social hibernation. In each building rest up to 20 parents and young animals close together, so that they can warm each other when the winter temperatures drop too strong. This increases the chances especially the young animals that have less energy reserves to survive even harsher winter.

Possible triggers for hibernation

The trigger for the prolonged hibernation external factors such as the drop in the ambient temperature or the lack of food were given in the fall traditional. But to the opinion of experts in addition to the shorter day lengths as a signal generator mainly internal factors such as changes in the hormonal balance - a decrease in the irradiation with ultraviolet light through the weaker sun leads to a lower production of vitamin D, which sets solidification hormones in gear - or the internal clock, which is subject to a seasonal rhythm, be responsible for the initiation of hibernation. Thus, the internal clock seems to be the formation of fat deposits and this in turn to influence the readiness to sleep. Even the narcotic effect of a higher concentration of carbon dioxide in the sleeping caves was discussed as a causative factor for hibernation.

Waking up in the spring

The exact cause for waking up in the spring is still not known. Rising ambient temperatures and the accumulation of too many waste products inside the body could serve as a wake-up signals. Anyway, the hibernators must gradually increase after his body temperature during the recovery phase. Hormonal influences ensure that the brown adipose tissue is broken down to produce heat for the purpose of energy gain. Are 15 degrees Celsius reached, the muscle tremors one to further increase in temperature. The chest and head area with the vital organs is heated faster than the rest of the body.

Negative effects of hibernation on memory performance

Research by the University of Vienna in ground squirrels have shown that the more month winter sleep has a negative impact on the memory performance of hibernators. In comparison to animals that had held no hibernation, the ground squirrel tasks had to be solved (for example, to find a way in the labyrinth or the lever of feeders to use ) after their long sleep phase no longer able to previously learned. One explanation could be the low neuronal activity during torpor. It has even been shown that connections between nerve cells in the brain during hibernation are degraded.

Hibernating Birds

The hibernation occurs not only in mammals. Even with some birds one knows hibernation -like states. To reduce the hummingbirds during starvation or cold spells their metabolism and fall into a sleep paralysis. In our latitudes are forfeited upon starvation young swifts during sleep in a poikilothermic ( cold-blooded ) state without the body temperature would so greatly reduced as in real hibernators. Longer periods of hibernation in mammals as it does not exist in birds, however.

Demarcation

Hibernation

The hibernation of brown bears in their dens should not be confused with the described hibernation, because the body temperature of bears during their prolonged dormancy never drops so much like the real hibernators. Winter rest periods without a major reduction in body temperature, there is also in badgers, squirrels and raccoons. The animal in question, however, are often awake during their winter rest and change more often the sleeping position. Brown bears mind spending up to seven months in their bear cave in a twilight sleep, releasing neither feces nor urinate and do not eat or drink, but live only on their fat reserves. American scientists have discovered that for this twilight the hibernation hormone Hibernation Induction Trigger ( HIT) is responsible. This substance allows the bear to survive their long winter rest, without losing muscle strength. A man would lose at a similar long resting phase, approximately in the hospital bed, about 90 percent of his muscle strength.

Winter resting states in deer

Recently, also a resting state was found with a drop in body temperature up to 15 degrees Celsius in native deer in winter. By reducing their metabolic activity in the nocturnal rest period, the animals are able to better survive the cold season. Attempts by the Veterinary University of Vienna showed that these regulatory mechanisms of body temperature and metabolism are influenced by the food supply. Protein-rich food that is not typical for the winter time, could be responsible for unnecessarily high metabolic activity during the winter. A non- species- winter feeding could thus produce hunger in the spring, because the metabolism has not been reduced, which in turn leads to browsing damage in the forest.

Researchers at the University of Veterinary Medicine Vienna assume that the demarcation of hibernation of winter dormancy is no longer tenable, but a variety of mammals over a range of similar running regulatory mechanisms of reduction of metabolism and body temperature feature that may also harbor seals and whales are used for longer dives.

The hibernation of cold-blooded animals

Stand out is the hibernation also of hibernation, as many poikilothermic animals - occurs in temperate climates - snails, some insects, most reptiles (snakes, turtles, lizards ) and amphibians ( toads, frogs ). In contrast to hibernation during hibernation homoiothermer animals the body temperature remains regulated even in the lowered position and is actively increases frostbite. Newts spend 3 to 4 months, slow worms and adders 4 to 5 months, tree frogs and lizards 5 to 6 months in a state of hibernation. A complete, deadly freezing of body fluids is prevented by glucose. In addition, the North American forest frog Rana sylvatica secretes during hibernation from any urine so that the urea content of his blood in order to increase fifty times.

The summer or dry sleeping

Another phenomenon is the summer sleep, the crocodiles and snakes (eg, the death adder ), usually hidden from the hot regions during the dry season under a sludge blanket, hold. A similar summer or dry sleeping hold in Central Europe in the heat and lack of water and the snails. More summer sleeping animals are some frog and toad species such as the Ornate Horned Frog ( Ceratophrys ornata ) or the African bullfrog ( Pyxicephalus adspersus ). The aim of the summer sleep is the hot and food is scarce time to save energy while; For this purpose, take the summer sleeper, just like the winter dormant animals, their metabolism down. In the amphibian above additionally reduces the size of the gut by over 40 percent. Along with the intestinal contraction is a decrease in nutrient uptake by about 60 percent. Once again there is food, the intestine grows back to normal size.