Close-up of a female black bear sleeping in den

Torpor

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.

Watch video clips from past programmes (3 clips)

In order to see this content you need to have an up-to-date version of Flash installed and Javascript turned on.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.