MEPS 444:289-301 (2012)  -  doi:10.3354/meps09371

Active hunting by deep-diving sperm whales: 3D dive profiles and maneuvers during bursts of speed

Kagari Aoki1,*, Masao Amano2, Kyoichi Mori3,6, Aya Kourogi2, Tsunemi Kubodera4, Nobuyuki Miyazaki5

1International Coastal Research Centre, Atmosphere and Ocean Research Institute, The University of Tokyo, Otsuchi, Iwate 028-1102, Japan
2Faculty of Fisheries, Nagasaki University, Bunkyo, Nagasaki, 852-8521, Japan
3Ogasawara Whale Watching Association, Chichijima, Ogasawara, Tokyo 100-2101, Japan
4Department of Zoology, National Science Museum, Shinjuku, Tokyo 169-0073, Japan
5Center for International Cooperation, Ocean Research Institute, The University of Tokyo, Nakano, Tokyo 164-8639, Japan
6Present address: Department of Animal Sciences, Teikyo University of Science & Technology, Uenohara, Yamanashi 409-0193, Japan

ABSTRACT: Active hunting pursuit can involve high expenditures of energy and therefore requires appropriately high-energy gains from successful prey capture. Using data loggers deployed on 12 sperm whales off the Ogasawara Islands, we regularly recorded bursts of speed during deep dives. Here, we analyzed speed, acceleration, and 3D data from these maneuvers to describe the whales’ hunting behavior. Bursts occurred at depths >400 m. The median number of bursts was only 1 per dive (range: 0 to 6 per dive), and 33% of the dives did not include any bursts, suggesting prey capture may not always require bursts. Bursts of speed averaged 3.4 ± 1.0 m s–1 (mean ± SD; maximum: 8 m s–1), more than twice the mean speed observed during dives (1.5 ± 0.2 m s–1). Bursts were generally divided into two phases: (1) rapid acceleration with active stroking, and (2) drastic deceleration and changes in body orientation. Tagged whales swam up to 405 m (mean: 120 ± 88 m) during these two phases. Such behavior suggests chasing of their prey, and should incur high energy expenditure. A large percentage (20 ± 14%) of the drag-related locomotion cost of the dives was spent in bursts. Two major types of bursts were observed: inflectional bursts with turning (87%) and linear bursts without turning (13%). Our results strongly indicate that sperm whales use an active-pursuit hunting strategy and use the bursts only to catch powerful and nutritious prey (i.e. large and/or muscular) that compensate for the energetic cost of the burst.

KEY WORDS: Diving behavior · Hunting tactic · Hunting strategy · Swim speed · Data logger · Physeter macrocephalus · Cetacean

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Cite this article as: Aoki K, Amano M, Mori K, Kourogi A, Kubodera T, Miyazaki N (2012) Active hunting by deep-diving sperm whales: 3D dive profiles and maneuvers during bursts of speed. Mar Ecol Prog Ser 444:289-301

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