<I>Rhinolophus hipposideros </I>has declined across its range. This study aimed to investigate aspects of its roosting, reproductive and foraging ecology which may have caused this decline. <I>R. hipposideros </I>is confined to south west Britain. It selects roosts in areas of undulating countryside with hedgerows and tree lines. Roosts were located predominantly in the roof voids of 19^th century buildings with stone walls and slate roofs, close to woodland and connected to it by hedgerows or tree lines. <I>R. hipposideros </I>has a long gestation period (78 days) and proportionately larger neonate (34% mothers mass) compared to other bat species. Post-natal growth was one of the fastest recorded for a bat species. The number of pups produced by colonies averaged 38% of pre-parturition counts of adults. Ambient temperature in May was shown to influence the reproductive phenology of this species. Patterns of roost occupancy and activity were investigated in a maternity, satellite, night and hibernation roost. Numbers of adults in the maternity roost peaked just before parturition. The timing of emergence and return from the maternity roost each night was correlated with ambient light levels. The duration of foraging each night was correlated with date and was reduced on nights with heavy rainfall. The importance of night roosts to heavily pregnant bats was demonstrated. During the winter most feeding took place before the end of December but successful foraging occurred throughout the winter. <I>R. hipposideros </I>foraged in woodlands, hedgerows and tree lines within 2-3 km of the maternity roost. It hunted close to vegetative clutter catching prey by hawking, gleaning and in late pregnancy by fly-catching, using hedgerows and tree lines as commuting routes between foraging areas and roosts. The implications of this study for the conservation of this species are discussed and management recommendations made.