Hibernation

This article refers to the process of hibernation in biology. For other uses, see Hibernate.

Hibernation is a state of regulated hypothermia, lasting several days or weeks, that allows animals to conserve energy during the winter. During hibernation animals slow their metabolism to a very low level, with body temperature and breathing rates lowered, gradually using up the body fat reserves stored during the warmer months. Some hibernating animals stir as often as once a week; others sleep throughout the season. Some reptile species are said to bruminate, or undergo brumination, but this is merely another term for hibernation, usually in the context of an induced hibernation in captivity necessary to reset the animal's biological clock for a new breeding season.

Both land-dwelling and aquatic mammals hibernate. Some examples of animals that hibernate include bats, ground squirrels, the European Hedgehog, terrapins, snakes, frogs, and newts. Although Pliny the Elderthought that swallowshibernated, and even a keen observer like the Rev. Gilbert White(The Natural History of Selborne) believed that, birds typically do not hibernate, instead using torpor, but a rare bird known as the Poorwilldoes hibernate. Aquatic animals can hibernate either in or out of water. Red-eared Terrapinshibernate in water, burying themselves in the mud at the bottom of a pond. Newts are capable of hibernation on land or in water.

One animal that some consider to be a hibernator but is not a true hibernator is the bear. While its heart rate is slow, the bear's body temperature remains relatively stable and it can be easily aroused. Other non-hibernators that are commonly assumed to be hibernators include badgers, raccoons, and opossums.

Before entering hibernation most species eat a large amount of food and store energy in fat deposits in order to survive the winter. Some species of mammals hibernate while gestatingyoung, which are born shortly after the mother stops hibernating. Hibernation is believed to come about due to increased production of the thyronamineswhich have the effect of lowering body temperature and inhibiting neuronal activity.

For a couple of generations during the 20th centuryit was thought that basking sharkssettled to the floor of the North Seaand hibernated. Tracking devices installed on 20 basking sharks in 2002dispelled this hypothesis.

Until recently no primate, and no tropicalmammal, was known to hibernate. However, animal physiologist Kathrin Dausmannof Philipps University of Marburg, Germanyand coworkers present evidence in the 24 June2004edition of Naturethat the Madagascan fat-tailed dwarf lemurhibernates in tree holes for seven months of the year. This is interesting because Madagascanwinter temperatures sometimes rise to over 30 °C (86 °F), so hibernation is not exclusively an adaptation to low ambient temperatures. The hibernation of this lemur is strongly dependent on the thermal behaviour of its tree hole: if the hole is poorly insulated, the lemur's body temperature fluctuates widely, passively following the ambient temperature; if well insulated, the body temperature stays fairly constant and the animal undergoes regular spells of arousal. Dausmann found that hypometabolism in hibernating animals is not necessarily coupled to a low body temperature.

Noise and vibration from snowmobiles, all-terrain vehicles and the like is said to sometimes awaken hibernating animals, who may suffer severely or die as a result of premature awakening in times of food shortage.

See also

• Estivation- a state of dormancy similar to hibernation, except it is used in the summer
• Torpor- regulated hypothermia for less than a day, often used by birds
• Hibernation induction trigger

External links

• Hibernation on Demand

Several of the species listed her as hibernators are ancient species--snakes, newts, bats, frogs. Questions as to the paleontological history of hibernation are important to ask. The issue could use discussion here.

The geographic distribution of hibernators and extinct hibernators would be important additions to this article.

Hibernation can also occur with satellites. Several current NASA missions can be kept in a low activity orbit or movement for a long period of time in order to conserve fuel.

James T. Struck

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Hibernation Wikipedia article Hibernation.