Why use the finite difference time domain method for studying echolocation bats?

Abstract

To study bat echolocation, it is essential to investigate echoes containing environmental information that bats use to determine their behavior. However, even with the recent advanced technique, it is difficult to measure all echoes reaching the bats in flight. Therefore, we proposed an approach that combines behavioral measurements (flight path measurements using high-speed video cameras and emitted ultrasound measurements using a telemetry microphone attached to the bat's back) with the FDTD method to calculate echoes from the surroundings, resulting in new behavioral findings. Analysis of binaural echoes reaching the bats in flight suggested the space composed of echo information is different from the visually perceived space, and the Doppler shift compensation behavior of bats revealed the transition of attention during flight by extracting echoes that bats pay attention to. In addition, by introducing a 3D digital model of a bat's head into the simulation space, we were able to study the echo information required for bat source localization based on the head transfer function. The proposed method enables the acquisition of echoes, which has been a longstanding problem in bat echolocation research and is a promising new method that could lead to a better understanding of bat behavior decisions.