Alternative use of two different roost types by a maternity colony of the lesser horseshoe bat (Rhinolophus hipposideros)

The lesser horseshoe bat (Rhinolophus hipposideros) is a threatened species in Germany with an estimated total of only 1800-2000 individuals. One of the largest known maternity colonies of this species is found in Altenberga/Thuringia, where 137 adult animals and 67 alive young were counted in the summer of 2000. As maternity roosts the bats used either the beer cellar of a local restaurant or the loft of the village church. When air temperature outside the roosts decreased during the reproduction period, increasing numbers of bats chose to spend the day in the colder beer cellar instead of the warmer church loft. The ambient temperature at 22:00 CEST of the previous night had the greatest effect on day roost choice. The strong correlation between the number of animals in the roosts and ambient temperature ceased at the time of fledging when the energetic constraints of the adult females probably decreased. Our study demonstrates that lesser horseshoe bats form maternity colonies not only in the well-known warm roosts, but can also successfully raise young in cold roosts. The opportunity to choose between different roost types seems to be energetically beneficial for breeding in this species and should, therefore, be preserved in conservation projects. © 2005 Deutsche Gesellschaft für Säugetierkunde. Published by Elsevier Gmbh. All rights reserved.