Why do macaroni penguins choose shallow body angles that result in longer descent and ascent durations?
Sato K; Charrassin JB; Bost CA; Naito Y National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173-8515, Japan. katsu@wakame.ori.u-tokyo.ac.jp It is generally assumed that air-breathing aquatic animals always choose the shortest route to minimize duration for transit between the surface and foraging depth in order to maximize the proportion of time spent foraging. However, empirical data indicate that the body angles of some diving animals are rarely vertical during descent and ascent. Why do they choose shallower body angles that result in longer descent and ascent durations? To investigate this question, we attached acceleration data loggers to eight female macaroni penguins, breeding on the Kerguelen Islands (48 degrees 45′-50 degrees 00′ S, 68 degrees 45′-70 degrees 58′ E; South Indian Ocean), to record depth, two-dimensional acceleration (stroke cycle frequency and body angle) and temperature. We investigated how they controlled body angle and allocated their submerged
