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Physiology Astate of winter dormancy and hypothermia seen in bears and other animals
Synonym(s): winter sleep.
hibernationa state of dormancy entered into by many animals during the winter, particularly those in cooler latitudes. Some temperate and arctic mammals, reptiles and some amphibians hibernate and, in this state, the METABOLISM is slowed down and the body temperature falls. Hibernation is generally triggered by cold weather and whilst body temperatures in mammals normally are maintained at the usual level, they may fall much lower and near to freezing point (in e.g. hamster), or to that of the surroundings (in e.g. bat).
True hibernators tend to be mid-sized animals as these can have sufficient food reserves without too large a surface area for heat loss. Bears are not true hibernators as their body temperature does not drop and they are able to awake from their winter ‘sleep’ very quickly. In temperate situations, rises in temperature may cause some animals temporarily to come out of hibernation. Compare AESTIVATION (1).