Constraints in the roost-site selection of the tree-dwelling Bechstein’s bat ( Myotis bechsteinii ).

Abstract

The roosting and foraging habitats of tree-dwelling Bechstein's bats can vary greatly. We hypothesised that the most important determining variables would not vary between different forest habitats and that social constraints may play a role in limiting commuting distances between roosting and foraging sites. Altogether 11 post-lactating adult females were radio-tracked in two predominantly oak forest habitats, where both potential roost and tree stand characteristics differed. We recorded 18 roosts; the distances between occupied roosts and commuting distances to foraging areas were measured. Within a 0.1 ha wide plot centred on each roost, a total of 17 habitat variables were recorded. Regardless of the different habitat structure (canopy closure, stand density) and roost-site availability, tracked females selected tree hollows with similar dimensions. The size of both roosting and foraging areas did not differ between habitats. We suggest that protection from predators and social constraints may determine the spatial distribution of Bechstein's bat roosts.