title: Bats' avoidance of real and virtual objects: implications for the sonar coding of object size.
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.
authors.affiliation: Neurobiology, Dept. Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Martinsried, Germany. holger.goerlitz@bristol.ac.uk
authors.forename: Holger R
authors.initials: HR
authors.lastname: Goerlitz
authors.forename: Daria
authors.initials: D
authors.lastname: Genzel
authors.forename: Lutz
authors.initials: L
authors.lastname: Wiegrebe
mesh_terms: D000162:Acoustics; D000818:Animals; D001307:Auditory Perception / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology*; D002685:Chiroptera / Q000502:physiology*; D004455:Echolocation / Q000502:physiology*; D009949:Orientation / Q000502:physiology*