Newborn bats (called "pups") weight 20–35% of their mother's body weight and are completely dependent on their mother. The young's large body size is believed to lead to high-energy expenditure from the mother, which is what limits her to only having one offspring a year. Adult males and females may use the same rock outcrops, but as is typical for other bats in the genus, the sexes typically roost separately from one another. In Virginia, both sexes appear to roost alone or occasionally in pairs, except females begin to congregate into maternity groups around the time pups are born and likely maintain these "maternity colonies" until pups are weaned. Size of maternity colonies is not well studied, but they appear to form smaller groups than other bats in the genus.