The Use of Ultrasonic Detectors in the Study of Bat Communities

I conducted two separate field studies to evaluate the effectiveness of Anabat II ultasonic detectors as a tool for use in the study of bat communities. I conducted a survey of bat communities in Missouri during the summer of 1998 using both mist nets and Anabat. To test, the relative merits of these two survey methods, I sampled a variety of habitats including ponds, streams, and flyways using Anabat and mist nets in a paired design. This allowed for the simultaneous sampling of bat community activity necessary for direct comparison. Echolocation calls recorded by the Anabat were identified using a discriminate function analysis model based upon a library of known call sequences. Overall, species richness was significantly higher for Anabat II than for mist nets, and was higher with Anabat for all habitats. Seven individual species and one species group were detected more frequently with Anabat than with mist nets. I also examined levels of intraspecific variation in search-phase calls of 7 species of vespertilionid bats from several locations in the eastern the central United States. Echolocation calls were recorded from light-tagged bats using the Anabat II detector and associated software. Analook software was used to calculate values for 5 parameters of calls: duration, maximum frequency, minimum frequency, frequency of the body, and slope of the body. My results indicate that most intraspecific variability in calls was attributable to differences among individuals and within individual call sequences. Observed levels of geographic variation, although significant in all species examined, were comparatively small and showed no trends among areas. Overall, my results indicate that the Anabat II ultrasonic detector is a very effective ecological tool, particularly for use in the survey and inventory of bat communities