Variability in sensitivity of Anabat II bat detectors and a method of calibration

Use of bat detectors can be an effective method of comparing relative amoun ts of activity of bats among areas. If multiple detectors are used, differe nces in sensitivity of detectors could bias results. We investigated the va riability in sensitivity and field of detection of 14 Anabat II bat detecto rs. Levels of sensitivity varied among detectors, greatly affecting relativ e sizes of the fields of detection. Calibration using an ultrasonic signal source can minimize variability in sensitivity among detectors.