Variation in bat detections due to detector orientation in a forest.

Abstract

Bat detectors are widely used to compare bat activity among habitats. We placed 8 Anabat II detectors at 2 heights. 3 directions and 2 angles with respect to horizontal to evaluate the effect of detector orientation on the number of bat detections received. The orientation receiving the maximum number of detections had 70% more detections than the mean of the 7 other orientation on the same night. We found that detectors on 1.4-m stands received 30% more detections than detectors placed directly on the ground. Detectors oriented toward the direction with the fewest trees received 24-44% more bat detections than those oriented in 2 other direction. We hypothesize that many of the noises we could not positively identify as bats were actually poorly recorded bat calls. Listening to audiotapes may be more efficient than visual inspection of time-frequency displays for comparison of bat activity among habitats when species identification is not important. Studies that standardize methods among sites and maximize the number of bat detections received at a site via detector placement will be most effective. (OCR version currently unavailable)

Citation

Weller, Theodore J.; Zabel Cynthia J. 2002. Variation in bat detections due to detector orientation in a forest. Wildlife Society Bulletin 2002. 30(3):922-930