Wildlife is a major reservoir for diseases transmittable to domestic ~mals and man. Following the death of a Scottish bat worker in 2002 from European bat lyssavirus type 2 (EBLV-2), for which Daubenton's bat is the only known UK vector, a study was established to investigate the roosting ecology and population genetic structure of this bat in order to understand the extent ofbat movements within and among populations. Forty-six individuals from six c.l1lonies were radio-tracked during the summers of2004-2006. Their daily movements between day roosts varied according to their reproductive state and the roost type used. Non-reproductive, pregnant, lactating and post-lactating females changed roosts on average every 1.5,3.9,5.0 and 2.3 days, respectively, although high fidelity to roosting areas was observed. Juveniles and reproductive females were more faithful to their maternity roosts in buildings than in trees. Despite significant differences between the temperature inside building and tree roosts, no difference in average skin temperature or torpor duration was found between lactating females at either roost type. However, torpor was used by post-lactating females at tree roosts for much longer than those at building roosts, and females roosting in frees, but not in buildings, expanded their foraging range during lactation. This may reflect the energetic advantages of building roosts. The spatial pattern ofmicrosatellite and mitochondrial DNA variation was examined to infer patterns of dispersal of bats among 35 sites throughout Scotland. DNA sequence variation at the mitochondrial control region and ND1 genes revealed two distinct clades. However, variation at eight microsatellite loci showed particularly low levels ofgenetic divergence among populations, even between populations from the two distinct mtDNA clades, suggesting a high level of dispersal among Daubenton's bat populations, with sex-specific differences in gene flow at large scales. The mobility ofadult Daubenton's bats andjuvenile dispersal are likely to be important in the epidemiology ofEBLV-2 epidemiology as they indicate the potential for spreading the disease. The large numbers ofDaubenton's bat using the same maternity roosts in buildings is also a risk factor in disease transmission as is the discovery that many .maternity roosts in trees and buildings were shared with other bat species.