In true hibernators, body temperatures drop to near ambient and heart rate slows drastically, but the animals periodically rouse themselves to urinate or defecate and to eat from stored food. The body temperature of bears, on the other hand, drops only a few degrees from normal and heart rate slows only slightly. They normally do not wake during this "hibernation", and therefore do not eat, drink, urinate or defecate the entire period. Higher body heat and being easily roused may be adaptations, because females give birth to their cubs during this winter sleep.
Of all mammals, North American bears continue to fascinate my adult mind, as much of what I remember being taught about them as a child isn't nearly what they're capable of.
This immediately reminds me of the Animal Planet piece this year chronicling Charlie Vandergaw's story of feeding black and grizzly bears on his property (Stranger Among Bears). This show was made possible mostly due to the work of photographer/filmmaker Richard Terry. Check out this audio commentary by Richard while browsing amazing photos of his time with the beautiful animals, and realize he had already seen Werner Herzog's Grizzly Man.
Always let them know where you are, what you are doing.
[caption id="attachment_28004" align="aligncenter" width="500" caption="Photo: Juliet Mills"][/caption]
Wiki (Top photo: Ursus americanus, Wikimedia)