SELECTION OF MATERNITY ROOSTS BY BIG BROWN BATS

Exclusion is the recommended method for removing roosting bats from bu ildings, but is often difficult to accomplish. A simpler way to limit bat-human conflicts may be to modify new and existing buildings to dis courage colonies from initially taking up residence. An understanding of the physical and microclimatic characteristics of maternity roosts is a prerequisite when modifying buildings to discourage colonies. We investigated Factors influencing maternity roost selection in big brow n bats (Eptesicus fuscus) by comparing characteristics of bat-occupied buildings with bat-unoccupied buildings at 10 sites. Bat-occupied bui ldings were significantly older, more likely to have galvanized steel (tin) roofs, more accessible to bats, and taller than randomly selecte d unoccupied buildings. In paired surveys, occupied attics were signif icantly more accessible to bats than physically similar unoccupied att ics and exhibited significantly higher temperatures and wider temperat ure gradients. Disturbance levels, light levels, and humidity did not differ between occupied and paired unoccupied attics. To discourage ba ts from initially establishing a maternity roost within a building, li mit all access points. In buildings where this is difficult, attics ca n be made less suitable as roost sites by reducing attic temperatures during the summer months. Bat boxes intended to house displaced matern ity colonies should be designed to provide high daily temperatures and wide temperature gradients.