Clusters may consist of hundreds of bats per square foot. A few species reside in caves year-round, although they usually use different caves in summer than winter. Most cave bats are very loyal to certain caves and return year after year to the same caves, often to the exact location in the cave where they spent the previous winter. Tree bats seldom enter caves. They roost in trees during summer days and spend winter primarily in hollow trees.
Several species make relatively long migration flights between winter and summer habitats.