Date of Award
Master of Science
Wildlife and Fisheries Science
Emma Willcox, David Buehler
Wildlife acoustic monitoring technologies have been advancing detection capabilities in many areas of species monitoring. Detection of species using remotely deployed technologies such as acoustic detectors provides population data with little effort, supplying critical information for many research analyses. Acoustic echolocation detectors have been used to detect and identify bats for several years, with constant improvements to the technologies utilized by these detectors. Because of the limitations associated with using a ground-based detection technology to monitor species flying at unknown altitudes, we designed and tested an Aerial Bat Detection Technology (ABDT) to monitor bats in flight at various altitudes (25m, 50m, 75m and 100m) above ground level. In addition, we tested the detection distance of Pettersson D500x (Pettersson Elektronik AB, Sweden) and SM2+ (Wildlife Acoustics Inc., Massachusetts, US) ultrasonic bat detectors, both of which are regularly used as part of bat monitoring programs. The ABDT was flown nightly for 3 months during the summer of 2016 and data collected by the ABDT was compared to data collected by a stationary ground-based acoustic detector run simultaneously in the same location. Of the 44 sampling nights, the ABDT recorded species missed by the ground-based detector on 20 nights. The total number of species and calls recorded by the two methods did not differ (P= 0.676 and P= 0.122, respectively) but calls/hr were different during the hours when the ABDT was located at 50m—100m (P= 0.017, P= 0.001 and P= 0.005, respectively). The ABDT generally recorded fewer calls/hr at 50 – 100 m altitudes but detected species that were not recorded on the ground-based detector. Upon testing the acoustic detectors using a signal emitted at a constant frequency between 8 – 65 kHz (102.2 dB – 44.92dB, respectively, at 1m), we found that the maximum detection distances were much shorter than expected for both the Pettersson D500x and the SM2+, with the maximum detection distances being 17m and 22m, respectively. This information suggests that current ground-based acoustic bat detection methods likely provide an incomplete representation of bat communities in the eastern United States and that an aerial detector can enhance the overall monitoring approach.
Dykstra, Adrienne Michelle, "Effectiveness of Aerial and Ground-Based Acoustic Bat Detection Technologies. " Master's Thesis, University of Tennessee, 2018.