Hibernation the summer months is aestivation. Often associated with low temperatures, the function of hibernation is to conserve energy when sufficient food is unavailable. 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 the entire winter. Larger species become hyperphagic, eating a large amount of food and storing the energy
Chionophile colder conditions arrive, animals go into a state of suspended animation called hibernation, when they go into a state of inactivity for long periods of time, which they do not come out of until more suitable conditions for them to survive in arrive. However, when animals live in an environment that is inhospitable for much of the year, then hibernation is not necessary. One of the few animals that does so are lemmings, which have a mass migration after they come out of dormancy. However, most animals living in the arctic would still be active, even during the most brutal