Drone exploration of bat echolocation: A UAV-borne multimicrophone array to study bat echolocation.

Area of Science:

• Bioacoustics
• Ecology
• Robotics

Background:

• Multimicrophone arrays are vital for studying bat echolocation but are limited by deployment location and mobility.
• Unmanned aerial vehicles (UAVs) offer potential for wider deployment but introduce concerns about noise interference and behavioral impacts on bats.

Purpose of the Study:

• To develop and test a UAV-borne multimicrophone system for recording bat echolocation in various environments.
• To assess and mitigate the effects of UAV noise on recording quality.
• To evaluate the behavioral impact of the UAV on bats during recordings.

Main Methods:

• Designed a UAV-borne multimicrophone setup.
• Quantified and mitigated UAV noise, particularly at ultrasonic frequencies.
• Deployed the system to record echolocation calls from four Danish bat species.
• Acoustically localized bat vocalizations.

Main Results:

• UAV noise was substantial at ultrasonic frequencies but was attenuated below system self-noise by suspending the array 30m below the UAV.
• Successful recording and acoustic localization of *Pipistrellus pygmaeus*, *Myotis daubentonii*, *Eptesicus serotinus*, and *Nyctalus noctula* were achieved.
• Bats exhibited minimal behavioral changes, approaching the array closely and emitting feeding buzzes.

Conclusions:

• UAV-borne multimicrophone arrays are a viable tool for studying bat echolocation across diverse and previously inaccessible habitats.
• This technology can provide crucial insights into bat sonar usage in their natural environments.
• The system effectively overcomes noise and behavioral challenges associated with UAV deployment.