There is a strong maternal bond and the young bats squawk when the mother is away. The young bats, however, grow quickly, being able to fly within three weeks. After two months, many of the young bats have left the nursery roosts, with male bats leaving before female. Behavior Townsend's big-eared bats are usually only observed at night. In the summer, the females form nesting roost.
Males are solitary during the maternity periods.
The maternity colonies consist of one or more small clusters, which rarely exceed 100 bats. Mating usually occurs in two phases. In the summer phase, both partners are alert and active, in a time known as the active phase. During the winter, or the passive phase, the females are torpid and the males seek out and find these females and mate with them. Townsend's big-eared bats begin to form their hibernation roosts in late October and by January, when group size is at its peak.