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First published online December 14, 2005
Journal of Experimental Biology 209, 152-157 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.01975

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The absence of spatial echo suppression in the echolocating bats Megaderma lyra and Phyllostomus discolor

Maike Schuchmann, Matthias Hübner and Lutz Wiegrebe^*

Department Biologie II, Universität München, Großhadernerstrasse 2, 82152 Planegg-Martinsried, Germany

View larger version (40K): [in a new window]   Fig. 1. Characteristic samples of a Megaderma lyra echolocation call (left) and a Phyllostomus discolor call (right). The upper panels show the spectrograms (the shaded bar shows the magnitude in dB); the lower panels show the oscillograms. M. lyra emits brief (0.5-1.5 ms), broadband, multi-harmonic echolocation calls. The fundamental frequency is frequency modulated from about 26 to 19 kHz. The strongest harmonics are the 3rd, 4th or 5th. P. discolor also emits brief (<3 ms), broadband, multi-harmonic echolocation calls covering the frequency range between 40 and 90 kHz. The fundamental frequency is modulated from about 23.5 to 16 kHz.

View larger version (26K): [in a new window]   Fig. 2. Experimental designs for Megaderma lyra (A,B) and Phyllostomus discolor (C). The layout consisted of a starting perch and two ultrasonic speakers (ls), each of which was associated with a feeding dish (fd) next to the speakers. The angle between the speakers in the M. lyra experiments was 90°. This angle was positioned at an elevation of 45° (B). A microphone (mic) was placed in front of the bat's head to pick up its ultrasonic emissions. The P. discolor layout was a Y-shaped maze (45x30 cm; wire mesh); the angle between the two legs was 45°. The inner width of each leg was 10 cm.

View larger version (29K): [in a new window]   Fig. 3. Echo suppression in the echolocating bat Megaderma lyra. The figure shows the percentage decisions towards the first of two reflections plotted against the lead-lag delay. Chance performance is represented by the horizontal broken line at 50%; significant performance is represented by the dotted line at 75%. The bats' performance in the lead-only trials is shown by the short horizontal lines. A-E show data for individuals; F shows the mean performance of all bats. The two data plots in A,C,E show a first (solid line) and second (broken line) data acquisition of these bats. Only one of five M. lyra individuals spontaneously showed significant preference (>75%) for the first of two reflections (C; first acquisition).

View larger version (19K): [in a new window]   Fig. 4. Echo suppression in the echolocating bat Phyllostomus discolor. The figure shows the decision towards the first of two reflections plotted against the lead-lag delay. Data are shown in the same format as in Fig. 3. The two data plots represent data from the two P. discolor individuals. None of these showed significant spontaneous preference for the first of two reflections.