They are abundant in California, Arizona, and New Mexico, where they winter. They winter in southern California, southeastern United States, Mexico, and Guatemala, but have also been found in Michigan, New York and Connecticut during December and in Indiana during January. This suggests that some may winter farther north than was previously expected. Sexes are generally only found together in parts of Nebraska, Montana, and the Badlands of South Dakota. Males and females are usually separated during the warmer months in North America, except during the mating season.
Females appear to be more concentrated in the western part of North America.
There is evidence for an altitudinal separation of sexes in California, with females concentrated in the lowlands and coastal valleys and males higher up in the foothills and mountains. The body of the hoary bat is about the size of a fat mouse. The wingspan is 17 inches. The bat has a blunt, rounded nose and small, beady eyes. The ears are short, thick, broad, and rounded.