Prey pursuit strategy of Japanese horseshoe bats during an in-flight target-selection task
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The prey pursuit behavior of Japanese horseshoe bats (Rhinolophus ferrumequinum nippon) was investigated by tasking bats during flight with choosing between two tethered fluttering moths. Echolocation pulses were recorded using a telemetry microphone mounted on the bat combined with a 17-channel horizontal microphone array to measure pulse directions. Flight paths of the bat and moths were monitored using two high-speed video cameras. Acoustical measurements of returning echoes from fluttering moths were first collected using an ultrasonic loudspeaker, turning the head direction of the moth relative to the loudspeaker from 0° (front) to 180° (back) in the horizontal plane. The amount of acoustical glints caused by moth fluttering varied with the sound direction, reaching a maximum at 70°–100° in the horizontal plane. In the flight experiment, moths chosen by the bat fluttered within or moved across these angles relative to the bat’s pulse direction, which would cause maximum dynamic changes in the frequency and amplitude of acoustical glints during flight. These results suggest that echoes with acoustical glints containing the strongest frequency and amplitude modulations appear to attract bats for prey selection.
KeywordsAcoustical glints Fluttering moths Pulse direction
Constant frequency component with a second harmonic
Initial frequency modulated
Terminal frequency modulated
We thank Dr. Takuma Takanashi and Dr. Ryo Nakano for their valuable support. We also thank Nobutaka Urano for assistance in capturing bats in the field. This work was partly supported by a Grant-in-Aid for Young Scientists (A) (Grant No. 70449510) from the Japan Society for the Promotion of Science (JSPS). These experiments complied with the Principles of Animal Care, publication no. 86-23, revised 1985, of the National Institutes of Health, and with current Japanese laws. All experiments were approved by the Animal Experiment Committee at Doshisha University.
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