[Characterization and comparison of the doppler compensation acoustic wave in Hipposideros armiger]

We used the pendulum device to study Doppler-shifted compensation of great leaf-nosed bat (Hipposideros armiger). The bats' echolocation calls were recorded by the Ultrasound Detector both under the rest condition and Doppler shift condition. Then we analyzed the calls with Avisoft software. Our results suggested that when H. armiger was approaching the target, it showed positive Doppler shift compensation: call frequency and the velocity (v) were positive correlated. Call frequency fell to minimum when the bats' relative velocity reached to maximum; likewise call frequency raised to the resting condition frequency when the relative velocity became zero. Negative Doppler shift compensation occurred when bats were far away from the target. Under negative Doppler shift compensation condition, we found call frequency and velocity were positive correlated as well, and moreover, call frequency raised to maximum again while the bats had their minus direction's maximal relative velocity. However, under this status, the elevated value was much lower than the depressed value under positive compensation at the same velocity. The frequency of occurrence of negative compensation was obviously less frequent than that under positive compensation condition. Therefore, we inferred that the two characteristics of the negative Doppler shift compensation mentioned above may be the coactions consequence of the bio-structural restriction and natural selection.