The spatial ecology of a species underpins an array of important questions about the ecology and evolution of a species, relating for instance to sociality, population dynamics, geographical distribution or genetic partitioning. Furthermore, the understanding of the spatial ecology of a species also has important implications for conservation and for disease management. It is in this context that I have examined the spatial ecology of the serotine bat (Eptesicus serotinus), in Europe, and especially at the northern limit of its distribution in England, using population genetic and stable isotope analyses. Data from nuclear microsatellite markers indicated higher levels of gene flow on the continent than in England. Consistent with this, England was separated into three genetically distinct populations, inter-connected by male-driven gene flow. Substantial asymmetric gene movement over the English Channel was inferred, possibly indicating a northward and westward range expansion. Mitochondrial DNA revealed fast population expansion and strong female philopatry. Moving to finer scale, δ13C in wing tissue and fur revealed that the association of individuals at roosts is flexible and dynamic, possibly reflecting their membership to communities operating at larger geographic scales. Communities of E. serotinus seem therefore to create a network of roosts with individuals continually re-assorting among themselves both within and across breeding seasons. The integration of the genetic and isotopic data highlighted complex spatial, social and temporal interactions in this species. While individual associations within communities seem to be flexible, communities were found to be strongly segregated over the breeding season. In contrast, genetic connectivity operates on a larger geographical scale than the local summer landscape. Together, these findings help explain the apparent absence in the UK of the European Bat Lyssavirus 1 (EBLV-1) for which this species is the main host. Hence, the relative fragmentation of this low-density population may inhibit the virus’ spread. However, with regular immigration from the continent, EBLV-1 could eventually enter the UK.