Bats reject clutter interference for moving targets more successfully than for stationary ones

Abstract

1. Using a discrimination task, we studied the detection of stationary and moving targets in the presence of background clutter by trainedEptesicus fuscus (Figs. 1, 2). 2. During the test, the amplitude of the target echo was always larger than that of the background echoes at the bat-to-target distance of 30, 50 and 80 cm. At the bat-to-target distance of 110cm, the target echo and background echoes had about the same amplitude (Fig. 3). 3. An electric motor was used to oscillate a target. The frequency content of the motor noise was mostly below 3 kHz (Fig. 4). 4. Monaural ear-plugging reduced the auditory sensitivity of a bat by an average of 33.6 ±11.2 dB over its most sensitive frequency range which is between 15 and 50kHz (Fig. 5). It also reduced a bat's detection of a target (Figs. 6, 8). 5. The detection of stationary and moving targets decreased with increasing bat-to-target distance (Figs. 6–8). However, a bat rejected clutter interference for a moving target more successfully than for a stationary one even when one of its ears was plugged (Figs. 7, 8).