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 amounts of activity of bats among areas. If multiple detectors are used, differences in sensitivity of detectors could bias results. We investigated the variability in sensitivity and field of detection of 14 Anabat II bat detectors. Levels of sensitivity varied among detectors, greatly affecting relative sizes of the fields of detection. Calibration using an ultrasonic signal source can minimize variability in sensitivity among detectors.