BatFlash: A head-mounted LED for detecting bat echolocation

Studies of bat echolocation and flight typically involve microphone array recordings from the ground, sometimes synchronized with video recordings. When multiple bats interact, it is often a challenge to assign a given call to the vocalizing bat. We have designed a lightweight, inexpensive device to display bat-tagged echolocation events using a head-mounted light-emitting diode (LED) that flashes when an onboard microphone detects a high-amplitude ultrasonic pulse. We describe the circuit and demonstrate its functionality in flight on the head of a big brown bat.