No abstract

The eastern pipistrelle (Perimyotis subflavus) is relatively common and widespread throughout the eastern United States. In recent decades, the distribution of P. subflavus has expanded westward across the Great Plains, and little information exists on its natural history in this region. In east central Nebraska, we monitored the use of a mine by eastern pipistrelles for >1 year. A few males occupied the roost in summer, but during the period of hibernation (late September-early May), the mine was used by at least 30 individuals composed of both sexes. Most individuals first entered the mine during late September through mid-October and exited by mid-May, with numbers of individuals fluctuating throughout winter. In winter, most individuals roosted along outer passageways of the mine, but in other seasons individuals were scattered throughout the mine. Females had significantly greater body masses than males upon entering the mine in autumn and before exiting the mine in spring. Both sexes had significantly heavier body masses in autumn than in spring. Overall, 55% of individuals marked in spring returned in autumn. Males had a higher return rate (69%) than females (46%) over a single summer. Many aspects of the natural history of P. subflavus in Nebraska are similar to those reported from eastern but not from southern parts of its distribution.