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Buoyancy and maximal diving depth in penguins : do they control inhaling air volume?

Katsufumi Sato^1,*, Y. Naito¹, A. Kato¹, Y. Niizuma^2,3, Y. Watanuki², J. B. Charrassin⁴, C.-A. Bost⁵, Y. Handrich⁵ and Y. Le Maho⁵

¹ National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173-8515, Japan
² Laboratory of Applied Zoology, Faculty of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan
³ Japan Science and Technology Corporation, Domestic Research Fellow, Hokkaido National Fisheries Research Institute, Katsurakoi 116, Kushiro-shi 085-0820, Japan
⁴ Laboratoire d'Océanographie Physique, Muséum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris Cédex 05, France
⁵ Centre d'Ecologie et Physiologie Energétiques, Centre National de la Recherche Scientifique, 23 rue Becquerel, 67087 Strasbourg Cédex, France

View larger version (84K): [in a new window]   Fig. 1 Schematic diagram showing ascending angle (), buoyancy (FB), drag (FD) and downward lift (FL) acting on an ascending, gliding king penguin with a data logger attached. This photograph was taken at an aquarium.

View larger version (32K): [in a new window]   Fig. 2. Flipper beating (blue line) and dive profile (black line) for two Adélie penguins (A,B) and a king penguin (C). Swim speed is shown as a red line in C.

View larger version (35K): [in a new window]   Fig. 3. Relationships between dive depth and depth of flipper beat cessation in two king penguins (filled circles) and ten Adélie penguins (open triangles). Depths of flipper beat cessation are plotted as absolute depth (A) and as a percentage of dive depth (B).

View larger version (23K): [in a new window]   Fig. 4. Relationship between measured speed (thick black line) and simulated speed (colored dots and lines) during the passive ascent periods of a king penguin (A) and an Adélie penguin (B). Values beside the lines are air volume (1) that might be kept by birds ascending passively (1 atm) used in the model simulation. Measured decompression ratio and ascent angles are shown as thick black lines. Simulated decompression ratios and lift coefficients are also shown (colored dots and lines), assuming that each bird had 1.2 (A) or 0.9 litres (B) of air (1 atm). The depths at which the birds stopped flipper beating are indicated.

View larger version (18K): [in a new window]   Fig. 5. Relationship between dive depth and estimated air volume of two king penguins (A) and two Adélie penguins (B). Horizontal lines, calculated from body mass using a equation in Lasiewski and Calder (1971), indicate the expected air volumes of the respiratory system for each penguin.