title: Adaptive beam-width control of echolocation sounds by CF-FM bats, Rhinolophus ferrumequinum nippon, during prey-capture flight.
abstract: The echolocation sounds of Japanese CF-FM bats (Rhinolophus ferrumequinum nippon) were measured while the bats pursued a moth (Goniocraspidum pryeri) in a flight chamber. Using a 31-channel microphone array system, we investigated how CF-FM bats adjust pulse direction and beam width according to prey position. During the search and approach phases, the horizontal and vertical beam widths were ±22±5 and ±13±5 deg, respectively. When bats entered the terminal phase approximately 1 m from a moth, distinctive evasive flight by G. pryeri was sometimes observed. Simultaneously, the bats broadened the beam widths of some emissions in both the horizontal (44% of emitted echolocation pulses) and vertical planes (71%). The expanded beam widths were ±36±7 deg (horizontal) and ±30±9 deg (vertical). When moths began evasive flight, the tracking accuracy decreased compared with that during the approach phase. However, in 97% of emissions during the terminal phase, the beam width was wider than the misalignment (the angular difference between the pulse and target directions). These findings indicate that bats actively adjust their beam width to retain the moving target within a spatial echolocation window during the final capture stages.
authors.affiliation: Faculty of Engineering, Doshisha University, Kyotanabe 610-0321, Japan. shiryu@mail.doshisha.ac.jp
authors.forename: Naohiro
authors.initials: N
authors.lastname: Matsuta
authors.forename: Shizuko
authors.initials: S
authors.lastname: Hiryu
authors.forename: Emyo
authors.initials: E
authors.lastname: Fujioka
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Yamada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Riquimaroux
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology; D002685:Chiroptera / Q000502:physiology*; D004455:Echolocation / Q000502:physiology*; D005426:Flight, Animal / Q000502:physiology; D007564:Japan; D011235:Predatory Behavior / Q000502:physiology; D013018:Sound Spectrography; D014741:Video Recording; D014828:Vocalization, Animal / Q000502:physiology*