Roost selection by female Hemprich's long-eared bats

Abstract

Selection of suitable roosts by bats can have fitness benefits by providing shelter and a place to rear young. Assuming that lactating bats behave differently from, and have greater food requirements than pregnant bats, we predicted that near the end of pregnancy, desert-dwelling bats would move to roosts appropriate to their changing needs. We followed radio-tagged pregnant and lactating female Hemprich's long-eared bats, Otonycteris hemprichii, to their roosts and characterized the shape of 38 roosts by measuring their linear dimensions, compass direction of the outer rock face, roost temperature (Tr) and the distance from the roost to the bats’ main foraging site. We also compared roosts used by bats to randomly chosen “potential” roosts. During reproduction, female O. hemprichii roosted mainly in cracks. Throughout the bats’ reproductive period, most of the roosts faced the morning sun. Temperatures in roosts used by pregnant bats or distances to their main foraging site were not different from those used by lactating individuals. However, pregnant females used horizontal cracks while lactating females used vertical cracks. Comparing roosts used by bats to “potential” roosts, we found that the former had smaller daily amplitudes of Tr than the “potential” ones. Female O. hemprichii used only a small number of the available roosts in the area, and re-used some of them year after year. We suggest that, in contrast to bats that live in temperate habitats, O. hemprichii do not need to seek roosts with temperature conditions specific to the periods of pregnancy or lactation because natural changes in Tr suffice, and other factors are involved in the decision to choose a roost or to abandon it.