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First published online March 17, 2006
Journal of Experimental Biology 209, 1217-1230 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02128
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Swim speeds and stroke patterns in wing-propelled divers: a comparison among alcids and a penguin

Yutaka Watanuki1,*, Sarah Wanless2, Mike Harris2, James R. Lovvorn3, Masamine Miyazaki4,{dagger}, Hideji Tanaka1 and Katsufumi Sato5,{ddagger}

1 Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakodate, 041-8611, Japan
2 NERC Centre for Ecology and Hydrology, Banchory, Aberdeenshire AB31 4BW, UK
3 Department of Zoology, University of Wyoming, Laramie, WY 82071, USA
4 Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand
5 National Institute of Polar Research, 1-9-10 Itabashi-ku, Tokyo, 173-8515, Japan


Figure 1
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  		Fig. 1. A razorbill (RAZO) showing the position of the logger attached to the lower back feathers and the two acceleration axes (surge along the longitudinal body axis and heave along the dorsoventral axis). Photo of the data-logger is inserted.

 

Figure 2
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  		Fig. 2. Wing stroke and heave and surge acceleration in a videotaped rhinoceros auklet (RHAU) diving to 3 m depth. (A) Position of the carpal joint relative to the eye, (B) heave (solid line) and surge (dotted line) are plotted against time, and (C) diagram showing the positions of the eye (open circles) and carpal joint (crosses). Crosses along the line for surge in B indicate samples at 32 Hz. The positions of the carpal joint of the left wing were sampled at 0.06 s intervals (numbered 1-9) with the video-image. The positions of the carpal joint in A were shown as the distance (d in C) between the approximate trajectory of the eye and the carpal joint. The unit of distance was 1/10 of the maximum positive distance recorded. Horizontal broken bars in A indicate the duration of downstroke determined with video-image, and horizontal bars in B indicate the periods when the heave acceleration had a positive value.

 

Figure 3
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  		Fig. 3. Typical changes of heave (solid line) and surge (dotted line) acceleration of a common guillemot (COGU) and a little penguin (LIPE) during descent at depths of 2 m and 20 m and during the bottom phase of the dive. Crosses along the line for surge indicate samples at 64 Hz. Downstrokes were assumed to occur during periods of positive heave, as indicated by bold horizontal bars. For COGU, the second small peak of heave was observed at the end of the downstroke at 2 m and 20 m. The horizontal dotted bar in the panel for horizontal swimming during the bottom phase by COGU indicates a glide when there was little heave or surge. Circles show peaks of surge acceleration, indicating forward thrust during upstroke (filled circles) and downstroke (open circles).

 

Figure 4
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  		Fig. 4. Typical dive profile for dives to 20–30 m depth for Brünnich's guillemot (BRGU), common guillemot (COGU), razorbill (RAZO), rhinoceros auklet (RHAU) and little penguin (LIPE). Parts of the profile where the bird made strokes are indicated by filled circles. Note that none of the birds made strokes on their ascent above 15–20 m.

 

Figure 5
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  		Fig. 5. Changes in body angle (open circles) and speed (filled circles) during descent and ascent, based on eight dives from two Brünnich's guillemots (BRGU), 14 dives from four common guillemots (COGU), nine dives from four razorbills (RAZO), 16 dives from three rhinoceros auklets (RHAU) and seven dives from two little penguins (LIPE). Maximum depths for these sample dives were all between 20 and 30 m. To illustrate the effects of current depth on body angle and swim speed, mean body angle was calculated for each of 1–2 m, 2–5 m, 5–10 m, 10–15 m and 15–20 m depths, and means ± 1 s.d. (vertical bars) across 1-s samples are shown. Statistical testing was done using all 1-s samples. Note that axes for descent and ascent differ.

 

Figure 6
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  		Fig. 6. Changes in the duration of upstroke (open circles) and that of downstroke (closed circles), and the frequency of wing strokes (open squares) and that of peaks of surge acceleration (closed squares) during descent to 20 m depths. See legend of Fig. 5 for abbreviations of species names and further explanation. Statistical testing was done using all wing strokes.

 

Figure 7
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  		Fig. 7. Changes in the maximum upward heave on downstrokes (closed triangle), the maximum downward heave on upstrokes (open triangle), the maximum surge both on upstrokes (open circle) and downstrokes (closed circle). See legend of Fig. 5 for abbreviations of species names and further explanation.

 




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