Roost ecology of the brown long-eared bat (Plecotus auritus, Linnaeus 1758) in North-East Scotland
In Britain, the brown long-eared bat, Plecotus auritus, commonly uses the roof spaces of houses as summer roost sites. This study aimed to investigate the roost requirements of this species, particularly in relation to its foraging activity, the composition of colonies, the occupancy of roosts, and whether the selection of particular roost sites affected the fitness of the bats using them. Fifty-six roosts used by P.auritus were located within the study area, in north-east Scotland. By comparing the houses occupied by P.auritus to a random sample of buildings from the same area it was shown that this species preferentially roosted in buildings which were older, higher, and had more roof compartments which were fully lined with wood. In addition, the buildings used as roosts were closer to trees and water and had a large area of woodland within 0.5km. The mean temperature within roosts was 17.9°C, and they were significantly warmer than the random sample of buildings, which had a mean temperature of 16.7°C. When captured, bats were generally euthermic and warmer roost temperatures may have reduced the dependence on torpor. Radio tracking showed that bats foraged mainly in deciduous woodland in the vicinity of the roost, using a series of feeding sites to which they frequently returned, and which were occasionally shared with conspecifics. Females spent most of their foraging time within 0.5km of the roost, while males travelled further. Bats returned to the main roost on 77% of mornings, but also used alternative roost sites, which had cooler microclimates, following nights of low temperature. Colonies were evident in summer roosts between May and October, and the typical size of group seen within the roof was 15-20 bats.