Some North American bats migrate in the fall to find food or a better place to hibernate. They may fly long distances to find a suitable shelter that will protect them from the harsh winter weather. Most cave bats spend each winter in the same place, and each summer in the same roost. Bats of the tropics do not hibernate. The temperature and food supply there remain suitable all year.
Scientists know little about the migration of tropical bats.
Among many species of bats, the males and females occupy different roosts. The males and females of some species even live in different regions of a continent except during the mating season. The mating season, which lasts for only a few weeks, may occur during the spring, fall, or winter, depending on the species. The female may carry the male's sperm within her body for several months before she becomes pregnant. In the spring, pregnant bats may leave their usual colony and join together in a nursery colony, where they give birth and rear their young.