Animals depend on sensory feedback from their environment to guide locomotion. For example, visually guided animals using optical flow models to control their speed and estimate their distance to objects (e.g. Srinivasan, 1996). In this study, we investigated how the acoustic information guide locomotion of animals that use the hearing as primary sensory modality to guide and navigate in the dark, where visual information is unavailable. We studied flight and echolocation behaviour of big brown bats as they flew under infrared illumination through a corridor with walls constructed from a series of individual vertical wooden posts. The spacing between the posts on opposite walls of the corridor was experimentally manipulated to create a dense spatial structure / sparse and balanced / unbalanced. The flight paths of signals bat echolocation and were recorded with cameras at high speed infrared motion capture and ultrasonic microphones, respectively. As bats flying through the corridor, successive emissions biosonar returned waterfalls echo the walls of the corridor. Bats flew through the centre of the hallway when the pole spacing on opposite walls was balanced and closer to the coast with wider spacing pole when the opposing walls had an unbalanced density. In addition, the bats produced shorter duration of echolocation calls when they flew in the corridors with a smaller distance between the poles, suggesting that the influences of density congestion characteristics of sonar signals the bat. Flight speed and rate of echolocation call did not, however, vary with dense and sparse spacing between the poles forming the walls of the corridor. Overall, these data demonstrate that bats adjust their behaviour in flight and echolocation dynamically when traveling through complex acoustic environments.
Articles on 36 Ech0 Flying group: