Bats' avoidance of real and virtual objects: implications for the sonar coding of object size |
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Authors: | Goerlitz Holger R Genzel Daria Wiegrebe Lutz |
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Affiliation: | Neurobiology, Dept. Biology II, Ludwig-Maximilians-University Munich, Großhadernerstraße 2, 82152 Martinsried, Germany |
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Abstract: | Fast movement in complex environments requires the controlled evasion of obstacles. Sonar-based obstacle evasion involves analysing the acoustic features of object-echoes (e.g., echo amplitude) that correlate with this object's physical features (e.g., object size). Here, we investigated sonar-based obstacle evasion in bats emerging in groups from their day roost. Using video-recordings, we first show that the bats evaded a small real object (ultrasonic loudspeaker) despite the familiar flight situation. Secondly, we studied the sonar coding of object size by adding a larger virtual object. The virtual object echo was generated by real-time convolution of the bats’ calls with the acoustic impulse response of a large spherical disc and played from the loudspeaker. Contrary to the real object, the virtual object did not elicit evasive flight, despite the spectro-temporal similarity of real and virtual object echoes. Yet, their spatial echo features differ: virtual object echoes lack the spread of angles of incidence from which the echoes of large objects arrive at a bat's ears (sonar aperture). We hypothesise that this mismatch of spectro-temporal and spatial echo features caused the lack of virtual object evasion and suggest that the sonar aperture of object echoscapes contributes to the sonar coding of object size. |
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Keywords: | Biosonar Echolocation Echoscape Object size Perception Sonar aperture |
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