[Physiologic mechanisms of use of the Doppler effect in echolocation by Rhinolophus ferrumequinum bats]

During the flight, the greater horse-shoe bat R. ferrumequinum decreases the frequency in the medial part of the emmited signal in proportion to the relative target--bat velocity. The value of the decrease is approximately equal to the Doppler shift; as a result, the animal picks up the echo at its species specific frequency irrespectively of the flight velocity. Threshold curve of bat's auditory system plotted in terms of N4, exhibits a sharp turning peak with a slope of about 83 dB/kHz towards low frequencies. The species specific frequency lies between the frequencies corresponding to the highest and the lowest thresholds. The described peculiarities of emission and perception of signals allow to consider the orientation system in the bat as a Doppler compensating system which provides the effective detection and discrimination of moving targets (e.g., a prey), improves spatial characteristics of hearing and enables the animal to evaluate the velocity during approaching the target.