Definition for Hibernation
From Biology Forums Dictionary
1. The state of torpor in an animal over months.
2. Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and/or lower metabolic rate. Hibernating animals conserve energy, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate. Although traditionally reserved for "deep" hibernators such as rodents, the term has been redefined based on specialized metabolic reductions and many experts believe that the processes of daily torpor and hibernation form a continuum. Hibernation during summer months is known as aestivation. Some reptile species are said to brumate, or undergo brumation, but the connection to this phenomenon with hibernation is not clear.
Although often associated with cold temperatures, the root purpose of hibernation is to conserve food during a period when sufficient food is scarce. It is the animal's slowed metabolic rate which leads to a reduction in body temperature and not the other way around. Hibernation may last several days, weeks, or months depending on the species, ambient temperature, time of year, individual animal's body condition, and fur on the animal's body.
Before entering hibernation, most species eat a large amount of food and store energy in fat deposits to survive the winter. Some species of mammals hibernate while gestating young, which are either born while the mother hibernates or shortly afterwards.