ANIMAL BEHAVIOUR, 1998, 56, 909–917 Article No. ar980858 Roost selection in the pipistrelle bat, Pipistrellus pipistrellus (Chiroptera: Vespertilionidae), in northeast Scotland E. V. JENKINS*, T. LAINE², S. E. M ORGAN*, K. R. COLE* & J. R. SPEA KM AN* *Department of Zoology, University of Aberdeen ²Department of Biology, University of Oulu (Received 20 November 1997; initial acceptance 30 December 1997; final acceptance 27 March 1998; MS. number: 5707R) ABSTRACT Availability of suitable roost sites may limit bat distribution and abundance. We compared nine internal and 26 external features of 21 known roost buildings with those of 17 random buildings in northeast Scotland, U.K. (57 N) to assess whether pipistrelle bats, Pipistrellus pipistrellus (55-kHz phonotype) are selective in their use of roosts. Bats did not select roosts with specific structural attributes. Compared with random buildings, roosts were closer to a tree over 10 m tall and had a greater percentage cover (of trees over 10 m tall) within a radius of 50 m. Trees may provide benefits by providing shelter and thus ameliorating the microclimate of the roost. Cover may also provide protection from predators so that bats are able to emerge earlier, thus increasing foraging time. Bats in the present study emerged 11 min earlier from roosts with 29% cover than from roosts with 3% cover, potentially gaining as much as 10% of their daily energy requirements in this extra time. Roosts were also more likely to have linear vegetation elements leading away from them. These features may be important for navigation, foraging or predator avoidance. Compared with random buildings roosts were closer to and surrounded by a greater area of deciduous woodland within a radius of 0.5 km, had a greater area of coniferous woodland within a radius of 0.5 km, and were more likely to be found within 0.5 km of a major river. All these factors are likely to be beneficial for foraging. A logistic regression model indicated that percentage cover within 50 m of the building was the best predictor of the presence or absence of bats roosting in a building.  1998 The Association for the Study of Animal Behaviour During the summer months, temperate zone bats spend up to 20 h of each day within a day roost. These roosts provide protection from bad weather (Vaughan 1987 ) and from predators (Fenton 1983 ), and they also serve as sites for social interaction with conspecifics (Morrison 1980 ). They are, therefore, one of the most important features of a bat’s environment, and the choices made by bats with respect to the type and location of roost sites are likely to have a major impact on their survival and fitness (Vonhof & Barclay 1996 ). The majority of bat species roost inside natural struc- tures such as caves (e.g. Tadarida brasiliensis: Davis et al. 1962 ), rock crevices (e.g. Antrozous pallidus: Vaughan & O’Shea 1976 ), tree h oles (e.g. Nyctalus noctula: van Heerdt & Sluiter 1965 ) and spaces under bark (e.g. Myotis daub- entonii and M. bechsteinii: Cerveny ´ & Bu ¨rger 1989 ). More recently, artificial structures, such as houses, have been widely used and some species roost almost exclusively in these sites (e.g. Pipistrellus pipistrellus: Thompson 1992 ; Plecotus auritus: Entwistle et al. 1997 ). The specific type of roost site selected by different bat species may be determined by the morphology of the bat (Vaughan 1970 ), the temperature or humidity within the roost (Fenton & Rautenbach 1986 ; Churchill 1991 ; Entwistle et al. 1997 ), the proximity of the roost to suitable foraging and drinking areas (Tuttle 1976 ; Speakman et al. 1991 ; Entwistle et al. 1997 ), or other features of the landscape surrounding the roost (Wunder & Carey 1996 ). The risk of predation may also influence roost selection by bats. The influence of predation on roost selection has been studied previously in tree-roosting bats (Vonhof & Barclay 1996 ), but not in bats using artificial structures. Vonhof & Barclay (1996) found that tree-roosting bats in southern British Columbia (49 38 N) roosted in trees that were taller than a random sample of available trees, and they suggested that they did this to avoid terrestrial predators such as weasels (Mustelidae). Aerial predators Correspondence: J. R. Speakman, Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, U.K. (email: j.speakman@abdn.ac.uk). E. V. Jenkins is now at the Department of Biology, University of York, PO Box 373, York YO10 S7W , U.K. T. Laine is at the Department of Biology, University of Oulu, Linnanmaa, 90570 Oulu, Finland. 0003–3472/98/100909+09 $30.00/0  1998 The Association for the Study of Animal Behaviour 909