Living above the treeline: roosting ecology of the alpine bat Plecotus macrobullaris

Abstract

Little is known about the alpine bat community, but recent studies suggest that the alpine long-eared bat, Plecotus macrobullaris, commonly forages in alpine habitats, although most of its known roosting records are from locations situated below the treeline. Aiming to contribute to resolving this seemingly contradictory pattern of ecological preferences of P. macrobullaris, we carried out a radio-tracking study to (1) identify its roosts and unveil its roosting habitat preferences, (2) determine whether bats found foraging in alpine habitats do actually roost and breed in such high-mountain environments, and (3) test if any elevation-related sexual segregation occurs. We captured 117 alpine long-eared bats and radio-tracked 37 individuals to 54 roosts located at elevations between 1,450 and 2,430 m, 46 of them above the treeline. Bats used rock crevices (30 roosts), scree deposits (21) and buildings (3) for roosting, and most lactating and pregnant females relied on crevices. Bats selected areas with high meadow availability near the roost, while avoiding densely forested areas. Foraging areas and roosting sites were located at the same elevation, indicating that alpine long-eared bats use alpine areas for both roosting and foraging in the Pyrenees. Breeding females roosted at lower elevations than nulliparous females and males, though they remained above the treeline. Although being considerably different to the ecological preferences described so far in the Alps, the roosting behaviour we observed was consistent with some ecological traits, namely foraging and trophic behaviour, of P. macrobullaris, as well as its distribution pattern linked to mountain regions.