Challenges of acoustic monitoring of bats—A biosonar perspective

Acoustic monitoring of bats is increasingly used in biodiversity assessments and population monitoring. Besides accurate species identification, additional factors make it challenging to derive population trends, yet—sizes based on acoustic monitoring. Inter- and intra-species as well as individual variation of acoustic parameters and acoustic activity result in varying detection probability. Changes in environmental conditions result in a large changes in the volume monitored by the device. Differences in the devices used for acoustic monitoring make it inherently difficult to compare data collected with different devices. By broadcasting bat echolocation calls from various distances to monitoring devices, the acoustic parameters influencing the successful detection of a call were examined. A microphone array was used to track bats in the vicinity of monitoring devices and the distance between device and bat was measured for each call based on the time of arrival difference. The acoustic detection functi...