MARINE MAMMAL SCIENCE, 14(2);209 (April 1998)
Diving behaviour and performance of harbour porpoises, Phocoena phocoena, in Funka Bay, Hokkaido, Japan
Otani, S., Y. Naito, A. Kawamura, M. Kawasaki, S. Nishiwaki, A. Kato 1998
In oder to monitor the diving behavior of free-ranging cetaceans, micro data loggers, with pre-programmed release mechanisms, were attached to the dorsal fins of two female harbor porpoises (Phocoena phocoena) in Funka Bay, Hokkaido, Japan, in 1994. The two loggers were successfully recovered and a total of 141 h of diving data (depth and water temperature in 4,671 dives) was obtained. Both porpoises dived almost continuously, rarely exhibiting long-time rest at the surface. Maximum dive depth were 98.6 m and 70.8 m, respectively, with more than 70% of diving time at 20 m or less. Most shallow dives were V-shaped with no bottom time. The V-shaped dives were significantly shallower in dive depth and shorter dive induration than U- shaped dives. Descent rate was not constant during a dive. The deeper the depths, the faster the mean descent and initial descent rates. This suggests that porpoises have anticipated the depth to which they dive before initiating the dive itself.
PP98-1
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