Hibernation

Hibernation is a state of minimal activity and <a href="/facts/Metabolism/WxDrm8k5">metabolic</a> depression undergone by some animal species. Hibernation is a seasonal <a href="/facts/Heterothermy/5FHnMHnM">heterothermy</a> characterized by low body-temperature, slow breathing and heart-rate, and low <a href="/facts/Metabolic_rate/lrT2cwEe">metabolic rate</a>. It is most commonly used to pass through <a href="/facts/Winter/kSp26z8R">winter</a> months – called <a href="/facts/Overwintering/mnMLo6SQ">overwintering</a>.
Although traditionally reserved for "deep" hibernators such as <a href="/facts/Rodents/mT4m8QJq">rodents</a>, the term has been redefined to include animals such as <a href="/facts/Bear/Y973Q4FP">bears</a> and is now applied based on active metabolic suppression rather than any absolute decline in body temperature. Many experts believe that the processes of daily <a href="/facts/Torpor/IlGtqU22">torpor</a> and hibernation form a continuum and use similar mechanisms. The equivalent during the <a href="/facts/Summer/v3DY22Uq">summer</a> months is <a href="/facts/Aestivation/CBPssd7f">aestivation</a>.
Hibernation functions to conserve energy when sufficient food is not available. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature. Hibernation may last days, weeks, or months—depending on the species, ambient temperature, time of year, and the individual's body-condition. Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period, possibly as long as an entire winter. Larger species become <a href="/facts/Hyperphagia/F9hf1wRU">hyperphagic</a>, eating a large amount of food and storing the energy in their bodies in the form of fat deposits. In many small species, food caching replaces eating and becoming fat.
Some species of mammals hibernate while <a href="/facts/Gestation/QKgkykw5">gestating</a> young, which are born either while the mother hibernates or shortly afterwards. For example, female <a href="/facts/American_black_bear/lezPKsnd">black bears</a> go into hibernation during the winter months in order to give birth to their offspring. The pregnant mothers significantly increase their body mass prior to hibernation, and this increase is further reflected in the weight of the offspring. The fat accumulation enables them to provide a sufficiently warm and nurturing environment for their newborns. During hibernation, they subsequently lose 15–27% of their pre-hibernation weight by using their stored fats for energy.
Ectothermic animals also undergo periods of metabolic suppression and <a href="/facts/Dormancy/VqHprS5C">dormancy</a>, which in many invertebrates is referred to as <a href="/facts/Diapause/y4fPYEjC">diapause</a>. Some researchers and members of the public use the term <a href="/facts/Brumation/VqHprS5C">brumate</a> to describe winter dormancy of reptiles, but the more general term hibernation is believed adequate to refer to any winter dormancy. Many insects, such as the wasp <a href="/facts/Polistes_exclamans/9593BjLx">Polistes exclamans</a> and the beetle <a href="/facts/Bolitotherus/hfz1XEH3">Bolitotherus</a>, exhibit periods of dormancy which have often been referred to as hibernation, despite their ectothermy. <a href="/facts/Botany/PaIRoxnb">Botanists</a> may use the term "seed hibernation" to refer to a form of <a href="/facts/Seed_dormancy/YHaDQK3B">seed dormancy</a>.

Hibernation open-in-new

Hibernation