Influence of forest composition and age on habitat use by bats in southwestern British Columbia

Abstract

Habitat use by bats in forests varies with environmental variables, clutter, and prey availability, but few studies have looked at habitat use as a function of forest composition and forest age across a range of elevations. We examined factors influencing habitat use of forest-dwelling bats in southwestern British Columbia using ultrasonic detection. We measured activity of three bat foraging guilds in four forest types and three age classes from May to August 2000 and 2001. Habitat use varied with forest composition and stand age, but not always as we predicted. Activity of open-habitat foragers (large bats) was greatest in higher elevation forests and in young forests. In contrast, activity of the long-eared myotis (Myotis evotis (H. Allen, 1864)), a gleaner, was greater in lower elevation black cottonwood (Populus trichocarpa Torr. & A. Gray ex Hook.) and cedar–hemlock stands. Myotis evotis activity also increased with increasing forest age. Activity of edge and gap insectivores (genus Myotis Kaup, 1829) was greater in black cottonwood stands and old Interior Douglas-fir stands than in other forest types. The probability of detecting foraging Myotis was highest in black cottonwood stands. Myotis activity did not show a clear pattern with forest age. Our results demonstrate the importance of black cottonwood riparian forests to foraging Myotis, as well as the importance of older, low-elevation forests.