Natural adaptations allow bears to survive for months without food or water during hibernation. Bears naturally lower their body temperature and utilize fat for energy. Bears use their own body fat as a source of fuel and nutrition, but do not eat, drink, urinate or have bowel movements while hibernating.
Bears start preparing ahead of time for hibernation. Before hibernating, bears eat and drink excessively to prepare for hibernation. They eat constantly and intake gallons of water a day. Once the bears have “fattened” themselves for hibernation, they begin to reduce activity levels in preparation for hibernation. They eat less and become increasingly sedentary. They reduce their breathing and oxygen intake, breathing once every 40-50 seconds.
Even though hibernation is associated with sleeping, bears do not sleep the entire time. Bears occasionally move around and reposition themselves to conserve heat. Hibernation means that they do not need to eat or drink, or perform normal excretory functions such as urination and defecation. Bears stay in their dens the entire time if possible. If a den is damaged or destroyed, bears leave and find a new location to hibernate. After bears emerge from hibernation, they slowly readjust to an active lifestyle. They start eating and drinking slowly as well as resuming normal excretory functions.