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

Summary

• 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).