Bears hibernate during the winter months in most areas of the world.
The denning period in YNP is approximately 5 months. For many years bears were not considered to be true hibernators. Mammals considered true, or deep hibernators, such as chipmunks and ground squirrels, experience a drastic decrease in body temperature during hibernation. Many researchers now consider bears to be super-hibernators. Respirations in bears decrease from 6-10 breaths per minute normally, to 1 breath every 45 seconds during hibernation.