Hibernation is a state where animals significantly reduce their metabolic rate, body temperature, heart rate and breathing to conserve energy during periods when food is scarce. Unlike sleep, which is primarily a mental change, hibernation involves drastic physiological changes, and waking a hibernating animal can be fatal due to the high ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.