Actually bears don't hibernate. Bears do what scientists call "winter lethargy," where they slowly lie dormant for a few months waking only a few times to eat. They do not defecate or urinate and their body temperature drops only about 10 degrees Fahrenheit. Their heart rate slows and their breathing is slowed as well. They do give birth during this period though and their bodies produce milk for the cub or cubs to drink. It is not technically hibernation but they do hibernate, kind-of
Animals that do hibernate, the ground squirrel for example, will drop their body temperatures as low as 32 degrees Fahrenheit or even lower, utilizing their body's high sugar content to keep from freezing solid. They enter dormancy fast and are hard to wake up. Bears enter slowly and can be aroused relatively easily.
Other animals, some frogs for example, actually freeze their body fluids during hibernation and lay completely frozen metabolically for several months during very cold winters.
But when they go out for "winter lethargy
' they eat a lot of food and stuff pinecones up the butt to
reduce pooping so they can live through the hard cold winter
When a bear is hibernating its breathing and heart rate slow down. They can go 100 days without food and water.