Potential for Niche Overlap in Roosting Sites Between Nycticeius humeralis (Evening Bats) and Eptesicus fuscus (Big Brown Bats)

Abstract

Many bat species have similar requirements for summer roosting sites leading to the potential for niche overlap and competition for roosts. Similarities in day roosts between bat species are rarely considered as a factor influencing population dynamics of species. We tracked Nycticeius humeralis (evening bats) and Eptesicus fuscus (big brown bats) to roost trees to evaluate the possibility of niche overlap in roost-site selection. Only tree height was significantly different between roosts used by the two species. Canopy cover, canopy height, dbh, tree species, tree condition, and roost type were not significantly different between the trees used by the two species. If competition for roosts exists between these species, similarities in roost trees may be important, especially as roost trees become scarce due to increased human alteration of roosting habitat. Competition for roost sites, in concert with other factors, may affect both competitors; however, populations of the inferior competitor, which is probably the evening bat, should be more negatively affected.