The use of exposed diurnal roosts in Alberta by the little brown bat, Myotis lucifugus

Abstract

The use of exposed diurnal roosts by the little brown bat,Myotis lucifugus, throughout the summer months is only known to occur among Alberta populations of this species. This study is the first to examine that behaviour. In total, 426 M. lucifugus using exposed anthropogenic surfaces as diurnal roosts were observed in the summers of 1985 and 1986. Bats were usually found alone, but groups of up to six individuals were seen. When found at these roosts, 98.8% of bats were at least 2 m from the ground and 95.1% were below an overhang. Bats were found on brick substrates in 89.0% of observations and in the corner between two surfaces in 57.0%. Bats were found on east-facing surfaces less frequently than expected under random distribution. Roost selection appears to have been based on several strategies, including thermoregulation, predator avoidance, and desiccation avoidance. After maternity roosts were vacated, the proportion of juveniles at exposed roosts was higher than their proportion in the total population. This may be the result of their inability to enter, or lack of knowledge of, many enclosed roosts used by adults.