Long-eared bats roost singly or in small colonies in caves, behind window shutters, under loose tree bark, in cliff crevices. Females gather in nursery colonies in attics, barns, and tree cavities. Probably a single young is born in July. Long-eared bats return to caves in fall, often sharing space with little brown bats, big brown bats and pipistrelle bats. The Indiana bat resembles the little brown bat, but has a pinkish cast to its fur, giving it a light purple-brown coloration.
Sexes are equal in size.
In winter, some 97 percent of the total species population hibernates in certain large caves in Missouri, Kentucky, Indiana, and Illinois. Pennsylvania is on the fringe of the species' range. Populations of Myotis sodalis are dwindling throughout its range, and it is on the federal endangered species list. The Indiana bat hibernates in clusters of about 250 bats per square foot on the ceilings and side walls of caves. A winter of repeated disturbances causes bats to burn vital fat stores, and they may run out of energy before spring.