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First published online October 21, 2004
Journal of Experimental Biology 207, 4057-4065 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01265

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Why do macaroni penguins choose shallow body angles that result in longer descent and ascent durations?

Katsufumi Sato^1,*, Jean-Benot Charrassin², Charles-André Bost^3, and Yasuhiko Naito¹

¹ National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173-8515, Japan
² Département Milieux et Peuplements Aquatiques, Muséum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France
³ Centre d'Ecologie et de Physiologie Energétiques, Centre National de la Recherche Scientifique, 23 rue Becquerel, F-67087 Strasbourg, France

View larger version (20K): [in a new window]   Fig. 1. Typical dive cycle of a macaroni penguin (MK8). The vertical broken lines delineate the separation of the dive into three phases: descent, bottom phase and ascent.

View larger version (16K): [in a new window]   Fig. 2. Relationships between dive depth and mean stroke cycle frequency during (A) descent, (B) bottom phase and (C) ascent. Data from all birds are represented (N=5351 for A and C; N=5027 for B).

View larger version (24K): [in a new window]   Fig. 3. Relationship between dive duration and depth for all dives (N=6952) made by eight macaroni penguins.

View larger version (22K): [in a new window]   Fig. 4. Relationships between (A) descent duration and bottom phase start depth and (B) ascent duration and bottom phase end depth. Data from all birds are represented (N=5352).

View larger version (24K): [in a new window]   Fig. 5. Relationships between (A) mean descent body angle and duration and (B) mean ascent body angle and duration of a macaroni penguin (MK1). Colours of plots represent ranges of bottom-phase start or end depths (black for <20 m, green for 20–40 m, red for 40–60 m, blue for >60 m).

View larger version (30K): [in a new window]   Fig. 6. Relationships between (A) bottom-phase duration and mean ascent body angle within a dive and (B) bottom-phase duration of a dive and mean descent body angle of a subsequent dive in a macaroni penguin (MK1). Colours of plots represent ranges of bottom-phase start or end depth (black for <20 m, green for 20–40 m, red for 40–60 m, blue for >60 m). Regression lines are for each depth range.

View larger version (21K): [in a new window]   Fig. 7. The maximum horizontal distance (H) travelled during the descent and ascent, which is calculated from depth (D) and body angle () using the equation H=D/|tan|. Colours of lines and values on lines represent the depth of bottom-phase start (descent) or end (ascent).