Convergence of reference frequencies by multiple CF–FM bats (Rhinolophus ferrumequinum nippon) during paired flights evaluated with onboard microphones
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The constant frequency component of the second harmonic (CF2) of echolocation sounds in Rhinolophus ferrumequinum nippon were measured using onboard telemetry microphones while the bats exhibited Doppler-shift compensation during flights with conspecifics. (1) The CF2 frequency of pulses emitted by individual bats at rest (F rest) showed a long-term gradual decline by 0.22 kHz on average over a period of 3 months. The mean neighboring F rest (interindividual differences in F rest between neighboring bats when the bats were arranged in ascending order according to F rest) ranged from 0.08 to 0.11 kHz among 18 bats in a laboratory colony. (2) The standard deviation of observed echo CF2 (reference frequency) for bats during paired flights ranged from 50 to 90 Hz, which was not significantly different from that during single flights. This finding suggests that during paired flights, bats exhibit Doppler-shift compensation with the same accuracy as when they fly alone. (3) In 60 % (n = 29) of the cases, the difference in the reference frequency between two bats during paired flights significantly decreased compared to when the bats flew alone. However, only 15 % of the cases (n = 7) showed a significant increase during paired flights. The difference in frequency between two bats did not increase even when the reference frequencies of the individuals were not statistically different during single flights.
KeywordsJamming avoidance Reference frequency Resting frequency Doppler-shift compensation
Constant frequency of the second harmonic component
Doppler-shifted constant frequency
Jamming avoidance response
These experiments complied with the Principles of Animal Care, publication no. 86-23, revised in 1985, of the National Institutes of Health, and with current Japanese laws. All experiments were approved by the Animal Experiment Committee of Doshisha University. This work was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas (Grant No. 20200055), a Grant-in-Aid for Young Scientists (B) (Grant No. 21760318) of JSPS and an ONR grant (Grant No. 00014-07-1-0858).
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