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From Wikipedia, the free encyclopedia
Hibernation is a state of minimal activity and metabolic depression.[1][2] Hibernation is seasonal heterothermy, typically occurring during the winter months.[2] It functions to conserve energy when sufficient food is unavailable, which is accomplished by decreasing metabolic rate, lowering body-temperature, slower breathing and heart-rate.[2] 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.
To achieve this energy saving process, ectothermic animals also undergo periods of metabolic suppression and dormancy, which in many invertebrates is referred to as diapause.[3] An endothermic animal decreases its metabolic rate and thereby its body temperature.[4]
Hibernation traditionally was reserved for "deep" hibernators such as rodents, but it has now been redefined to include animals such as bears.[5] It is now applied based on active metabolic suppression rather than any absolute decline in body temperature.[1] Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms.[1][4] The equivalent of hibernation during the summer months is aestivation.[6]
Hibernation induction trigger (HIT) is a chemical substance found in the blood of hibernating animals, and functions similar to opiates.[7] Although, there are arguments against it contributing to inducing hibernation.[8]