| Bats in the eastern United States use echolocation to locate prey and navigate in their surroundings. Recent advances in technology have enhanced use of ultrasonic detectors in field studies. Data recorded using ultrasonic detectors have been used to investigate a wide variety of questions involving ecology of bats. Despite their abundant use, fundamental questions remain unanswered on appropriate uses and limitations of this technology.; Using the Anabat II bat detector, acoustic identification of 12 bat species in the eastern United States was investigated using discriminant function analysis. Cross-validation yielded accuracy rates that ranged from 56.9% ( Lasiurus borealis) to 98.5% (Mottos greasiness), with 10 of 12 species having accuracy rates >70%. To assess the impact of ambient light levels on bat activity, passive recording was conducted with light intensity meters at three fixed stations in Kentucky. While temperature and time past sunset were significant factors in explaining variation in bat activity, ambient light level was not. Typically, bat habitat use studies assume equal bat activity throughout habitats being sampled. Using a 6-station grid, spatial variation of bat activity within two stands (mature forest and timber harvest area) was examined. Spatial variation in bat activity among stations was twice as high in the mature forest stand as in the timber harvest area, thereby suggesting that a different number of ultrasonic detectors is required to adequately sample bat activity in these habitats. Acoustic identification cannot be performed on all recorded echolocation calls. Thus, an objective filter was constructed to assess if call sequences were identifiable. Effect of habitat type on proportion of recorded calls surviving the filter was determined. Habitats with greater structural complexity (e.g., mature forests) had lower proportions of call sequences that were identifiable. Taken together, these studies assist in determination of appropriate uses of frequency division ultrasonic detectors for the study of bats. |
