A period of time, usually over the winter, when some animals go into a state of resting (torpor) or deep sleep to conserve energy. During hibernation they will slow their metabolism to very low levels, with body temperature and breathing rates lowered, gradually using up body fat which was stored up during the warmer months, during which the animal was active. The process to land based as well as aquatic animals, Eg. bears, mice, terrapins, newts. Aquatic animals can hibernate either in or out of water. Terrapins hibernate in water burying themselves in the mud at the bottom of a pond whereas newts can hibernate do either.