Target Ranging by Echolocating Bats in Interfering Noise

Abstract

This author has previously reported evidence that bats using short-duration FM sonar cries determine the range of a target from the arrival time of its echoes, and that these bats process returning echoes for their arrival time information with a correlation receiver. Bats of the species Phyllostomus hastatus were tested for their range discrimination acuity at several different echo S/N ratios to find out whether the bat behaved in a manner similar to a receiver operating on the correlation properties of its input. S/N ratios from better than 100 down to about 0.3 were used on the bats. The acuity of range resolution was stable at about 12 mm as the S/N ratio declined to about 2–5, at which point the bats acuity abruptly deteriorated. This performance strengthens the assertion that these bats have an ideal sonar receiver as far as range or time resolution is concerned.