Habitat selection by forest bats in relation to mixed-wood stand types and structure in central Ontario

Recent studies have suggested that old-growth forests may be important habitat for some species of bats, but the proximate factors related to greater bat activity in older forests are not well understood. To assess relative habitat use by bats, we used ultrasonic detectors and mist nets to sample bat activities among old-growth white pine (Pinus strobus) mixed woods, mature white pine mixed woods, boreal-type mixed woods, and selectively logged white pine mixed woods in central Ontario. We quantified 15 structural characteristics in the 21 stands sampled for bat activity. Detection rates of Myotis species, silver-haired bats (Lasionycteris nocitvagans), and hoary bats (Lasiurus cinereus) were 2.7-14.0 times greater in old-growth white pine mixed-wood stands than in other stand types (Ps < 0.05). Multivariate habitat models suggested that, between logged and uncut stands, the availability of potential roost sites may be an important determinant of bat activity for Myotis species and silver-haired bats. Among uncut stands, our habitat models suggested that snag availability was not an important variable affecting habitat selection by bats. Rather, bat detection rates in uncut forests were correlated with canopy and subcanopy structure. Little brown bats (Myotis lucifugus) and northern long-eared bats (M. septentrionalis) may spatially separate for feeding. To maintain habitat for bats, forest managers should implement timber harvest strategies that retain remnant old-growth white pine stands in the landscape, preserve snags and large live trees in selectively logged forests, and promote regeneration of second-growth white pine stands to old age rather than truncating age classes at younger ages.