Close-up of a female black bear sleeping in den


Torpor is a form of sleep that helps animals conserve valuable resources in times of stress, such as in cold or very hot, dry weather. Body temperature drops and the heart and metabolic rates slow down so that less energy is needed to stay alive. Animals can stay torpid for short bursts, or go into long-term torpor lasting weeks or months, known as hibernation (winter) or aestivation (summer). Animals in torpor are far more difficult to wake up than animals in normal sleep.

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