RELATIVE ABUNDANCE AND HABITAT USE BY TREE BATS, LASIURUS SPP IN SOUTH-CENTRAL PENNSYLVANIA

We monitored bats with ultrasonic detectors at 39 localities represent ing nine habitat types in five southcentral Pennsylvania counties (Ada ms, Cumberland, Franklin, Fulton and York) froin 17 May to 13 Septembe r 1989 and 14 May to 6 September 1990. The principal objective was to assess the statuses of two species of solitary tree bats, the Red Bat (Lasiurus borealis) and Hoary Bat (Lasiurus cinereus), in southcentral Pennsylvania by determining the relative abundance and ecological dis tribution of these species in this region. On 77 nights we deployed we ather-proof remote monitoring units. each containing a frequency-tunab le ultrasonic detector, a voice-activated microcassette tape recorder. and a ''talking'' clock. We also sampled bats with mist nets on 33 ni ghts. Red Bats were detected at 24 localities (60.0%) and Hoary Bats a t 19 localities (47.5%). By comparison mouse-eared bats (Myotis spp). were recorded at 32 (80.0%) of the sites surveyed. Red Bats were detec ted on 42 detector survey nights (53.8%) and were netted on 16 nights (48.5%) in all nine habitats sampled. Hoary Bats were detected on 30 d etector survey nights (38.5%) in eight of nine habitats but were nette d only twice (6.1%), presumably because they foraged above the height sampled by the mist nets. Observed in all nine habitats. Myotis spp. w ere detected on 58 of 78 detector survey nights (74.4%), more often th en either Lasiurus species but were netted on only 11 nights (33.3%). Both Lasiurus species appear to be relatively abundant and ecologicall y widespread in southcentral Pennsylvania.