Some animals hibernate during the winter months because food is scarce. They go into a long slumber, skipping the morning hours when food is more plentiful (because their body temperature doesn’t drop), but many animals have taken advantage of this change, including jerboas, little brown bats, Eastern chipmunks, prairie dogs, and some species of squirrels. At least one species of bird is thought to hibernate; the poor wren of western North America. Know when it’s time to prepare for hibernation. While the exact mechanisms are unknown, shorter days, reduced food intake, and cold weather all seem to affect HIT, and build up large stores of white and brown fat in the body to help them get through it. Brown fat provides body heat and energy when the animal wakes up. Some animals also store food in their burrows to eat during brief periods of wakefulness. In fact, significant physiological changes occur in the body during hibernation. The animal’s body temperature drops, and its breathing and heart rate slow down. The effects can be so severe that hibernating animals appear to be dead. In regions with mild winters, animals may hibernate for only brief periods or not at all. During the long hibernation period, many animals wake up briefly to go to the bathroom and have a snack before going to sleep. Some bears are unique in that they do not wake up, eat, drink, or go to the bathroom during hibernation, which can last for months.