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First published online December 14, 2006
Journal of Experimental Biology 210, 56-64 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02618
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Echolocation signals of wild harbour porpoises, Phocoena phocoena

Anne Villadsgaard1,*, Magnus Wahlberg1,2 and Jakob Tougaard3

1 Department of Zoophysiology, Institute of Biological Sciences, University of Aarhus, C. F. Møllers Alle, DK-8000 Aarhus C., Denmark
2 Fjord & Bælt, Margrethes Plads 4, DK-5300 Kerteminde, Denmark
3 National Environmental Research Institute, Fredriksborgvej 399, DK-4000 Roskilde, Denmark


Figure 1
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  		Fig. 1. The experimental set up consists of a linear, vertical array of three (A,B,D) or four (A-D) hydrophones connected via a conditioning box to a digital recorder.

 

Figure 2
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  		Fig. 2. (A) Harbour porpoise click with signal envelope (dotted line) and the -10 dB duration of the click (horizontal line). (B) Accumulated energy content (%) in the click over time. The interval between the dotted lines is covering 95% of the energy content of the signal.

 

Figure 3
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  		Fig. 3. Results from the transmission loss measurements and acoustic ranging calibration, using an omni-directional calibrated sound source emitting harbour porpoise clicks at a known range from 3 m depth. (A) Received level (dB re 1 µPa pp) as a function of measured range for the 4-hydrophone array. The line is a transmission loss model consisting of spherical spreading and absorption. (B) RMS error (see text) in acoustic localization as a function of the measured range for the 4-hydrophone array and the 3-hydrophone array. (C) The maximum variation in the transmission loss due to ranging variation as a function of measured range for the 4-hydrophone array and the 3-hydrophone array.

 

Figure 4
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  		Fig. 4. The estimated apparent source level of harbour porpoise clicks as a function of the back-calculated range between the porpoise and the array.

 

Figure 5
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  		Fig. 5. Power spectrum of a harbour porpoise click (FFT size 64, spectrum interpolated with a factor 10, sampling rate 400 kHz, rectangular window).

 

Figure 6
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  		Fig. 6. Histogram of inter-click intervals (ICIs) from wild harbour porpoises (N=822; median 58 ms; s.d. 34 ms; bin width 10 ms).

 

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© The Company of Biologists Ltd 2007