QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online August 17, 2006
Journal of Experimental Biology 209, 3269-3280 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02402

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Watanabe, Y. Articles by Miyazaki, N. Search for Related Content PubMed PubMed Citation Articles by Watanabe, Y. Articles by Miyazaki, N.

Body density affects stroke patterns in Baikal seals

Yuuki Watanabe^1,*, Eugene A. Baranov^2,, Katsufumi Sato³, Yasuhiko Naito⁴ and Nobuyuki Miyazaki¹

¹ Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo 164-8639, Japan
² Limnological Institute, Siberian Division, Russian Academy of Sciences, Ulan-Batorskaya Street 3, Irkutsk 664033, Russia
³ International Coastal Research Center, Ocean Research Institute, The University of Tokyo, 2-106-1 Akahama, Otsuchi, Iwate 028-1102, Japan
⁴ National Institute of Polar Research, 1-9-10, Kaga, Itabashi, Tokyo 173-8515, Japan

View larger version (30K): [in a new window]   Fig. 1. Speed and swaying acceleration during stroke-and-glide swimming. Grey vertical bars denote periods of glide. Deceleration rates during glides were used to calculate drag. The experiment was conducted on July 6, 2005.

View larger version (42K): [in a new window]   Fig. 2. Typical dives made by (A) Individual 1 (June 19, 2003), (B) Individual 2 (June 22, 2003) and (C) Individual 3 (November 1, 2004), showing swimming speed, depth and swaying acceleration. Vertical broken lines separate dives into three phases: descent, bottom and ascent. Note that stroke patterns in descent and ascent differ among the individuals.

View larger version (38K): [in a new window]   Fig. 3. Relationship between stroke rate in descent and ascent for Individuals 1-3 in experiment 1 and Individual 4 in experiment 2. The diagonal line represents identical stroke rate in both directions.

View larger version (43K): [in a new window]   Fig. 4. Swimming speed, depth and swaying acceleration during typical shallow dives made by Individual 4 in (A) weighted and (B) unweighted conditions, and deep dives made in (C) weighted and (D) unweighted conditions on July 5, 2005 (A,C) and July 6, 2005 (B,D). Vertical broken lines separate dives into three phases: descent, bottom and ascent. Swimming behavior during descent and ascent is categorized as prolonged glide (white horizontal bar), stroke-and-glide swimming (grey horizontal bar) and continuous strokes (black horizontal bar) (see `Results' for categorization).

View larger version (23K): [in a new window]   Fig. 5. Occurrence of swimming modes categorized as prolonged glide (white horizontal bar), stroke-and-glide swimming (grey horizontal bar) and continuous strokes (black horizontal bar) in relation to maximum dive depth grouped into each 50 m (see `Results' for categorizing). Note that scales on x-axes differ between the weighted and unweighted conditions.

View larger version (24K): [in a new window]   Fig. 6. Relationship between measured speed (black line) and theoretical terminal speeds, assuming a total body density of 1043 kg m-3 (red line) and 1015 kg m-3 (blue line), during descent phases of dives for (A) weighted (July 5, 2005) and (B) unweighted (July 7, 2005) conditions. Depth, swaying acceleration and pitch (i.e. angle between long axis of seal's body and water surface, with positive values indicating ascent and negative descent) are also shown. Swimming behavior is categorized as prolonged glide (white horizontal bar) and stroke-and-glide swimming (grey horizontal bar) (see `Results' for categorization). Arrows indicate the first peaks of measured speed during prolonged glides.

View larger version (20K): [in a new window]   Fig. 7. Relationship between maximum speed in each prolonged glide measured at the depth of >100 m, and pitch at the moment when the speed was recorded, for weighted (solid diamonds) and unweighted (open diamonds) conditions. Pitch represents the angle between the long axis of the seal's body and the water surface, with negative values indicating descent. Theoretical terminal speeds for several body densities are shown as colored lines, with the density values in kg m-3 indicated by the numbers beside the lines. Strictly speaking, the theoretical lines are different between the conditions because of the different mass of the object (seal + weight=46.65 kg for the weighted condition; seal=45.2 kg for the unweighted condition; see Eqn 4) and should be shown separately. However, the difference in mass corresponds to a difference in theoretical terminal speed of only 1.6%. For clarity, we show the theoretical lines common to both conditions, based on the mean mass (45.9 kg).