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First published online February 1, 2008
Journal of Experimental Biology 211, 642-647 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.014118
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Shipboard measurements of the hearing of the white-beaked dolphin Lagenorhynchus albirostris

P. E. Nachtigall1,*, T. A. Mooney1, K. A. Taylor1, L. A. Miller2, M. H. Rasmussen2,3, T. Akamatsu4, J. Teilmann5, M. Linnenschmidt2 and G. A. Vikingsson6

1 Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii, PO Box 1106 Kailua, HI 96734 USA
2 Institute of Biology, SDU-Odense, Campusvej 55, DK-5230, Odense M, Denmark
3 Húsavik University Center, University of Iceland, Garðarsbraut 19, 640 Húsavik, Iceland
4 National Research Institute of Fisheries Engineering, 7620-7, Hasaki, Kamisu, Ibaraki 314-0408, Japan
5 National Environmental Research Institute, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
6 Marine Research Institute, Skúlagata 4, PO Box 1390, 121 Reykjavík, Iceland


Figure 1
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  		Fig. 1. Hoop catching method. The dolphin rides the bow and a small net placed in the hoop is put in front of the animal when it comes up to breathe. As it jumps through the hoop it is caught in the small net, which releases immediately from the hoop.

 

Figure 2
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  		Fig. 2. Maneuvering the female white-beaked dolphin into the stretcher.

 

Figure 3
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  		Fig. 3. Experimental plastic tank lined with open cell foam.

 

Figure 4
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  		Fig. 4. Ambient noise in the tank. (A) Waveform of the measured noise in a 1.5 s segment. (B) Noise spectral density (dB re. 1 µpa2/Hz) from 1 Hz to –500 kHz using a 1024-point FFT. The peak at 125 kHz and harmonics of this are weak system noise artifacts.

 

Figure 5
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  		Fig. 5. Sinusoidal amplitude modulated (SAM) stimulus recorded near the lower jaw of the male white-beaked dolphin during audiogram acquisition. The 181 kHz SAM stimulus was filtered between 10 and 200 kHz.

 

Figure 6
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  		Fig. 6. Sinusoidal envelope of a stimulus (lowest trace) and envelope following response of a 16 kHz tone from 110 dB to 60 dB re. 1 µPa in 10 dB steps (upper traces).

 

Figure 7
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  		Fig. 7. FFT of the envelope following response amplitudes of a white-beaked dolphin. Response (µV rms) is to a sinusoidal amplitude modulated (SAM) tone presented at a 16 kHz carrier frequency, a 1125 Hz modulation rate and stimulus intensities from 110 to 60 dB re. 1 µPa shown to the right of the graph.

 

Figure 8
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  		Fig. 8. Intensity of spectrum peaks of a 16 kHz tone (solid line, diamonds) at 1125 Hz at various pressure levels (SPL). Each point (diamond) represents an average of 1000 stimulus presentations. The linear regression of the spectrum peaks (broken line, open circles) is based on points from 70–110 dB. The threshold for the tone is defined as the point where the regression line crosses zero on the response scale, in this case 69.8 dB.

 

Figure 9
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  		Fig. 9. Partial and entire evoked potential audiogram of two white beaked dolphins, Lagenorhynchus albirostris. Female dolphin: broken line with open circles; male dolphin: solid line with black diamonds. The values above 100 kHz are 128 kHz, 152 kHz and 181 kHz.

 




© The Company of Biologists Ltd 2008