"The bats are pretty well trained to associate the music with food by the end of the first night, but to make sure that it really sinks in, I give them another night of reinforcement with just the music," says Geipel.
Afterward, when the bats are returned to the wild, Geipel plays the music again - and sure enough, the winged little music-lovers come flying in for the researcher to gather data about their use of echolocation.
"It not only brings the bats close enough for the microphones to record their echolocation calls but allows me to be fairly sure that the bats that I record in the forest are the same individuals that I recorded in the flight cage. It is highly unlikely that bats other than the ones I have trained would respond to the music," says Geipel.
The researcher says she chose the heavy metal music for its sonic qualities, going from hard to soft in a way that somewhat mirrors the call of the frogs they eat. As for the bats actually enjoying the musical genre without a food reward? That's an area for future study.