Response of the Doppler echolocation system in the bat, Rhinolophus ferrumequinum

James A. Simmons

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An electronic target simulator was used to produce artificial echoes for the echolocating bat, Rhinolophus ferrumequinum. When the bat was presented with Doppler‐shifted echoes, it changed the frequency of the constant‐frequency (CF) portions of its outgoing orientation sounds to restore the CF portions of returning echoes to the bat's preferred frequency, approximately 83 kHz. The data confirm previous observations of the Doppler‐compensating response in bats that use long‐duration CF signals. Theoretically, Rhinolophus could detect target velocity changes of 0.05 to 0.1 m/sec, and the bat actually detects changes in the velocity of a simulated target as small as 0.1 m/sec. The Doppler‐compensating response adapts the bat's frequency‐modulated (FM) echolocation system to prevailing target velocities, perhaps to stabilize echo images against perceptual distortions of target range that occur as a result of an interaction between FM sweeps and Doppler shift. The velocity‐sensitive sonar presumably allows the bat to detect moving prey against background of fixed objects.