There is evidence that sexes are separate during the warm months, females being more abundant in the northeastern U.S., males in the west. Both sexes occur on the winter range. Foraging flight of the hoary bat is fast and straight. Preferred sites are hidden from above, with few branches below, and have ground cover of low reflectivity. Females and young tend to roost at higher sites in trees.
Females bear young while roosting in trees, preferring sites as described under cover requirements.
Females may leave the young in the roosting site while foraging. Prefers open habitats or habitat mosaics, with access to trees for cover and open areas or habitat edges for feeding. Emerges late in the evening. Peak activity varies with season and location, but usually is 3-5 hr after sunset. Individuals wintering in cold climates hibernate, but may be active on warm winter days.