How Do Bats Hibernate?

            In winter, some bats will hibernate for several months, while others migrate to areas where insects are still to be found. Hibernating bats do not suffer in low temperatures even though, of all mammals, bats undergo the most dramatic change when they go into hibernation. Their body temperatures may drop below the freezing point of water.


            In North America, red bats have been found alive and perfectly healthy with body temperatures of -5C; they do not freeze solid because blood freezes at a lower temperature than water. Such bats often become covered with dew, which does freeze, and so they may spend several weeks encased in ice.


            When in hibernation, bats use only a tiny fraction of the energy they require when active. Whatever energy they do need is supplied from the fat reserves laid down at the end of summer. The fat is stored between the shoulders, and it is here that the highest temperature can be measured when the animal begins to emerge from its hibernating state.