FLEXIBILITY IN FORAGING AND ROOSTING BEHAVIOR BY THE BIG BROWN BAT (EPTESICUS-FUSCUS)

I used radiotelemetry to study the roosting and foraging behaviour of big brown bats (Eptesicus fuscus) in south central British Columbia. Maternity colonies were found in hollows of dead ponderosa pine trees (Pinus ponderosa) and colony members were not loyal to specific trees. Individuals consistently foraged above a 300-m stretch of the Okanagan River, travelling 1.8 km on average from day roosts to the foraging area. There were significant differences in the duration of foraging bouts among different sex and age-classes. The results are compared with data collected in a similar manner for a population in Ontario, where, in contrast to British Columbia, E. fuscus were highly loyal to man-made roost structures and on average travelled less than 1 km to foraging sites that varied nightly. I suggest that the marked difference in both roosting and foraging behaviour is due to differences in the availability and structure of roosts and in the distribution of insect prey.