Journal of Experimental Biology 202, 3121-3126 (1999)
Precise monitoring of porpoising behaviour of Adelie penguins determined using acceleration data loggers.
K. Yoda, K. Sato, Y. Niizuma, M. Kurita, C. -A. Bost, Y. Le Maho and Y. Naito
A new method using acceleration data loggers enabled us to measure the porpoising behavior of Adelie penguins (Pygoscelis adeliae), defined as a continuous rapid swimming with rhythmic serial leaps. Previous hydrodynamic models suggested that leaping would be energetically cheaper when an animal swims continuously at the depth near the surface within three maximum body diameter of an animal. In the present study, free-ranging Adelie penguins leapt at a mean speed of 2.8 m/s, above the predicted threshold speed (0.18 - 1.88 m/s). Wild penguins reduced drag by swimming deeper (0.91 m) and did not swim continuously within the high-drag layer while submerged. This indicates that previous calculations may be incomplete. Moreover, leaps represented an average of 3.8% of the total distance traveled during the porpoising cycle, which would make energy savings marginal. Among the six penguins used in our study, two did not porpoise and three porpoised for less than 7 min, also indicating that this behavior was not important during travel to and from foraging sites as has been previously suggested. Birds mainly porpoised at the start and end of a trip. One explanation of porpoising might be an escape behavior from predators.
PG99-3
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