The acoustic behavior of the fish-catching bat, N o c t i l i o l e p o r i n u s, during prey capture

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Abstract
Many bats change the acoustic parameters of their echolocation calls in a deliberate manner during prey capture. Attempts to quantify these changes have been either of limited scope or subject to potentially severe errors due to an inadequate consideration of the directionality of both the bat and the recording microphone. Therefore, the echolocation pulses emitted by two N. l e p o r i n u s have been recorded as they approached and captured stationary prey, with the microphone positioned in such a way that the structure of the pulses incident upon the target could be determined. The results of this study show that: (1) during the last 1.5 m of the approach, N. l e p o r i n u s reduces the intensity of emitted pulses by 6 dB per halving of distance, so that the intensity incident upon the target is constant; (2) at a point in the pulse train that corresponds to the position of the hypothesized tracking phase of echolocation, N. l e p o r i n u s selectively reduces the intensity of the frequency‐modulated (FM) fundamental so that the FM pulse component is predominantly second harmonic; and (3) a high degree of temporal overlap occurs between the FM component of emitted pulse and echo when N. l e p o r i n u s is within 0.4 m of its prey.

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