Habitat use by populations of the Big Brown Bat, Eptesicus fuscus, was compared in urban and rural areas using ultrasonic sensors. Field work was conducted in eastern Ontario and western Quebec in the summer of 1981. Rural E.fuscus foraging activity was  concentrated in residential zones, with high activity also occurring over water. Activity was low over rural parkland and farmland. Urban habitats did not show significant differences in levels of E. fuscus foraging activity, although the overall foraging rate was lower in the urban environment than in the rural.

The movements of individual Big Browns were monitored using radio telemetry. Tagged E. fuscus from both urban and rural environments used more than one diurnal roost; the possible adaptive value of roost switching for E.fuscus is discussed.

The consequences of urbanization for an insectivorous temperate-zone bat species are considered, with emphasis on differential prey availability and roost availability in urban and rural areas.