Habitat use by bats, Myotis spp., in western Newfoundland

Abstract

Bat diversity and activity patterns were monitored using mist-nets and bat detectors, and roosting habitat was investigated using radio-telemetry in western Newfoundland during June-August 1995. Of the three species of bat known to occur in Newfoundland (Lasiurus cinereus, Myotis lucifugus, and M. septentrionalis), only the latter two were detected or captured. Myotis bats were recorded with detectors at 87% of the riparian sample sites, although at relatively low levels (mean of 19.4 commuting passes/hr). These detector results suggest that myotis bats are ubiquitous, yet not very abundant in western Newfoundland. Most captures were of M. lucifugus (66%, n = 30), yet M. septentrionalis appear to be more common than previously thought, representing 34% (n = 15) of the captures. Myotis bats roosted in holes (n = 4), in cracks (n = 2), and under loose bark (n = 2) of standing dead trees, generally close to cutblock edges and sources of water (presumably foraging sites). Compared to those trees available (based on random transects in cutblocks and forests), bats did not appear to select roost trees based on many of the characteristics I measured (% bark remaining, diameter at breast height, stand slope, or species group (deciduous or conifer)). However, bats tended to select roost trees of smaller height classes (0-5 and 11-15 m) and with greater numbers of cavities than those available. Because most roosts were located along edge habitat, forest harvesting may increase accessibility to roosts for some bats by creating corridors and openings through the forest. However, it is still unclear how habitat fragmentation and loss of forested areas may affect bat populations.