Night Roosting Ecology of Pallid Bats (Antrozous pallidus) in Oregon

Abstract

-Many bats spend a significant part of the nocturnal activity period roosting, but little is known about the ecology of night roosts. Here, I report on the night roosting ecology of pallid bats (Antrozous pallidus) in central Oregon. Night roosts were located in buildings, under rock overhangs and under bridges. Roosts were protected from rain and wind and were spacious enough to allow free flight into and out of the roost. Eighty-five female pallid bats were captured in mist nets at night roosts in 2 yr (1990-1991). Up to six bats were caught entering a roost simultaneously. Recaptures of banded bats suggest bats are faithful to particular night roosts both within and between years. Radio-tracked bats captured at the same night roost did not necessarily roost together subsequently in diurnal roosts. Bats began entering the night roosts almost immediately after the onset of emergence from the day roosts. Activity at the roost was characterized by peaks, with many bats entering and leaving, and lulls, with few or no bats at the roost. These observations suggest the possibility of a social function of night roosting.