MEPS 349:277-287 (2007)  -  DOI:

Diel diving behavior of sperm whales off Japan

Kagari Aoki1,*, Masao Amano2, Motoi Yoshioka3, Kyoichi Mori4, Daisuke Tokuda3, Nobuyuki Miyazaki1

1Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo 164-8639, Japan
2 Department of Animal Sciences, Teikyo University of Science & Technology, 2525 Yatsusawa, Uenohara, Yamanashi 409-0193, Japan
3Graduate School of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan
4Ogasawara Whale Watching Association, Aza Higashi, Chichijima, Ogasawara, Tokyo 100-2101, Japan

ABSTRACT: Diel changes in the diving behavior of cetaceans have been documented only in some shallow divers, such as smaller toothed whales and some baleen whales. In this study, we attached data loggers to sperm whales Physeter macrocephalus, one of the deepest and longest divers among all marine mammals, to investigate the possible diel patterns in the species. We conducted the experiments in 2 areas off Japan (the Kumano Coast and the Ogasawara Islands). Obvious diel patterns of diving behavior were found off the Ogasawara Islands, where the whales dived deeper and swam faster during the day than at night (day-time depth: mean 853 ± 130 (SD) m, n = 35; night-time depth: mean 469 ± 122 m, n = 31; day-time velocity: mean 2.0 ± 0.3 m s–1, n = 20; night-time velocity: mean 1.5 ± 0.3 m s–1, n = 19). On the other hand, off the Kumano Coast, whales showed no diel rhythm in diving depths or swimming speed (day-time depth: mean 646 ± 212 m, n = 83; night-time depth: mean 561 ± 229 m, n = 44 and day-time velocity: mean 1.9 ± 0.5 m s–1, n = 57; night-time velocity: mean 1.6 ± 0.5 m s–1, n = 33). We suggest that the environmental differences between these 2 areas contributed to the difference in diel behavior of the whales, which was mediated by the diel behavior of their prey.

KEY WORDS: Sperm whales · Cetacean · Diving behavior · Diel patterns · Foraging · Thermocline

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Cite this article as: Aoki K, Amano M, Yoshioka M, Mori K, Tokuda D, Miyazaki N (2007) Diel diving behavior of sperm whales off Japan. Mar Ecol Prog Ser 349:277-287.

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