A comparison of 2 acoustical bat survey techniques

The use of ultrasonic detectors to survey the presence of bat species is common. Echolocation call quality differs between call sequences recorded directly to a laptop computer and sequences recorded to tape, but few studies have quantified the magnitude of difference and its potential effect on bat survey results. In 2000 we passively sampled 213 locations in northwest Georgia with an Anabat II bat detector (Titley Electronics, Ballina, Australia) linked to a tape recorder and actively sampled with an Anabat II detector linked to a laptop computer (hereafter referred to as tape recorder and laptop, respectively). We recorded 8,905 call sequences: 2,633 recorded by tape and 6,272 by laptop. On average the laptop recorded >2 times as many species/site as the tape recorder. Moreover, we detected 3 bat species with the laptop that we did not detect with the tape recorder. The laptop detected all species detected by the tape recorder. We were able to identify species on 53.2% of recorded calls on the laptop and only 28.0% of tape-recorder calls. Our results suggest that actively monitoring with an Anabat detector linked directly to a laptop computer records more bat call sequences and produces higher-quality call recordings, resulting in a more complete bat community survey than passively monitoring with an Anabat detector linked to a tape recorder.