At WiseGEEK, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.
Somewhere along the way, you may have been taught that bears hibernate during the winter. Technically, that’s not quite correct. Rather than hibernating, bears go into an inactive state called torpor, where many of the same physiological changes take place. Their heart rate, breathing and brain wave activity slow down significantly, as they conserve energy in the cold winter months when food is in short supply. Bears can wake suddenly from torpor if they sense danger, and females can give birth and then go right back into this uber-restful state.
All about hibernation:
- A hibernating animal’s metabolic rate slows to as low as 2 percent of normal levels and body temperatures can drop significantly. These changes don't occur during regular sleep.
- Some animals hibernate for months at a time, including squirrels, lemurs, chipmunks, mice, groundhogs, lizards, snakes, and bats. Migrating birds may enter torpor to save energy before long flights.
- During torpor, bears recycle their own urea (a byproduct of urine), and use water from their body fat, which allows them to stay hydrated.