Echolocation and flight behavior of the bat Hipposideros armiger terasensis in a structured corridor

In this study, the echolocation and flight behaviors of the Taiwanese leaf-nosed bat (Hipposideros armiger terasensis), which uses constant-frequency (CF) biosonar signals combined with a frequency-modulated (FM) sweep, are compared with those of the big brown bat (Eptesicus fuscus), which uses FM signals alone. The CF-FM bat flew through a corridor bounded by vertical poles on either side, and the inter-pole spacing of the walls was manipulated to create different echo flow conditions. The bat's flight trajectories and echolocation behaviors across corridor conditions were analyzed. Like the big brown bat, the Taiwanese leaf-nosed bat centered its flight trajectory within the corridor when the pole spacing was the same on the two walls. However, the two species showed different flight behaviors when the pole spacing differed on the two walls. While the big brown bat deviated from the corridor center towards the wall with sparse pole spacing, the Taiwanese leaf-nosed bat did not. Further, in comparison to E. fuscus, H. a. terasensis utilized different echolocation patterns showing a prevalence of grouping sounds into clusters of three. These findings indicate that the two species' distinct sonar signal designs contribute to their differences in flight trajectories in a structured corridor.