NOTES ONAWINTER COLONY OF BIGBROWN BATS AT WILLIAMSPORT, WARREN COUNTY, INDIANA

A single hibernaculum for big brown bats (Eptesicusfuscus) in the attic of a large old apartment building was studied over five winters. The number of bats generally increased during a period characterized by mild win- ters during which temperatures in the attic apparently always remained above freezing. However, many bats left during a very cold period in the late win- ter of 1993, when at least part of the attic reached temperatures below freez- ing. Turnover in the population using the attic was high both among years and within years. The bats spread out over the available area with essentially no clustering. The bats had a tendency to return to their favorite sections of the hibernaculum, but individuals almost never returned to the exact same spot. Sex ratios varied from 50.0% to 74.2% males. Several bats spent both the win- ter and summer in this roost.