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First published online October 18, 2006
Journal of Experimental Biology 209, 4238-4253 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02505
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Extreme diving of beaked whales

Peter L. Tyack1,*, Mark Johnson1, Natacha Aguilar Soto2, Albert Sturlese3 and Peter T. Madsen1,4

1 Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
2 Department of Animal Biology, La Laguna University, 38256 La Laguna, Tenerife, Canary Islands, Spain
3 BluWest, via Scarincio 12, 18100 Imperia (IM), Italy
4 Department of Zoophysiology, Biological Institute, University of Aarhus, Denmark


Figure 1
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  		Fig. 1. Representative sections of dive profiles from Ziphius cavirostris (A) and Mesoplodon densirostris (B). Intervals with regular click vocalizations are indicated by a thicker trace and times of buzzes are indicated by small open circles. The depth of occurrence of buzzes heard in the audio recording during the two dives is shown in the histogram on the right-hand side of each panel. The bin size of the histogram was 50 m.

 

Figure 2
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  		Fig. 2. Scatter plots of dive duration (A,C) and vertical speed (B,D) as functions of dive depth for all dives deeper than 20 m recorded on Ziphius cavirostris (A,B) and Mesoplodon densirostris (C,D). The plots in A and C show the surface-to-surface dive duration (dots) and the interval from the start to the end of regular clicking (unfilled triangles) in each dive. The absence of dive depths between 450 and 700 m for both species and the observation that only dives deeper than this range have consistent vocalizations leads us to define these as deep foraging dives (DFD). The plots in B and D show vertical speed (i.e. depth rate) as a function of dive depth during descents (downwards pointing black triangle) and ascents (upwards pointing unfilled triangle). The difference between descent and ascent rate for DFDs is apparent.

 

Figure 3
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  		Fig. 3. Dive profile (A) and fluke rate (B) for a Ziphius. Vocal phase and buzzes are marked on the dive profile. The average fluke rate in 1 min intervals, measured by counting cyclic variations in the pitch signal from the tag, is shown in the lower panel. The fluke rate is high in the first minute of both deep and shallow dives but then drops markedly during the remainder of the descent. Ascents, in comparison, feature more steady fluking.

 

Figure 4
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  		Fig. 4. Aligned dive profiles during inter-deep-dive-intervals (IDDIs) for Ziphius cavirostris (A) and Mesoplodon densirostris (B). The preceding deep dive ends at minute 0 whereas the following deep dive (not shown) starts after 10-142 min (Ziphius) or 25-181 min (Mesoplodon). The decreasing trend in the depth of shallow dives with time elapsed since the preceding deep dive is apparent.

 




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