Bat-detecting drones could help us find out what the animals get up to when flying. Ultrasonic detectors on drones in the air and on the water are listening in on bat calls, in the hope of discovering more about the mammals’ lives beyond the reach of ground-based monitoring devices.
Drone-builder Tom Moore and bat enthusiast Tom August have developed three different drones to listen for bat calls while patrolling a pre-planned route. Since launching the scheme, known as Project Erebus, in 2014, they have experimented with two flying drones and one motorised boat, all equipped with ultrasonic detectors.
The pair’s latest tests have demonstrated the detection capabilities of the two airborne drone models: a quadcopter and a fixed-wing drone. Last month, the quadcopter successfully followed a predetermined course and picked up simulated bat calls produced by an ultrasonic transmitter.
The bat signal
Moore says one of the major hurdles is detecting the call of bats over the noise of the drones’ propellers, which emit loud ultrasonic frequencies. They overcame this with the quadcopter by dangling the detector underneath the body and rotors of the drone.
This is not such a problem for the water-based drone. Last year, Moore and August tested a remote-controlled boat in Oxfordshire, UK, and picked up bat calls thought to belong to common pipistrelle and Daubenton’s bats. The different species often emit different ultrasonic frequencies.
“The amount of noise coming from the boat is almost zero – that turned out to be a really fantastic platform for recording bats on the water,” says August.
Since starting the project, the duo has experimented with a range of ultrasonic detection technologies. One lightweight detector from Peersonic produced exciting results early on. “We stuck it on the plane, test-flew it and that’s when we think we picked up our first bat call in flight,” says Moore. They are currently also using a detector by AudioMoth.
The drones can hear the bats from around 20 metres away, so they aren’t thought to pose any danger to the animals.
Little is known about what bats get up to high in the air, says ecologist Kate Jones at University College London, who studies bats.
“We’re monitoring on the ground and thinking that’s representative of the entire air column – but I don’t think that’s true,” she says.
It’s quite possible bats are commuting from site to site at higher altitudes. Using drones like this could give a more detailed picture of how bats move around than a handheld or ground-based sensor, says Jones. The bats are likely to just fly off if the drone got too close, she says.
Drones like those developed by Moore and August could also be useful for environmental surveys. For example, to determine whether placing wind turbines in a certain area could interfere with bats that are active far above the ground or tree canopy.
Source: New Scientist