鯨探機を利用して観察したマッコウクジラ群の遊泳行動〔英文〕

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Some observations of sperm whales in natural conditions were made with a sonar of 20kHz at night-time in the coastal waters of Japan in 1985 and 1987 on board a whaler. The whalesdove to a maximum of 730m, or 30-162m in respective means, during diving observations of 5-13h. The surfacing and diving Feriods of the whales were 1-32 min, or 9 min in mean, and 1-47 min, or 10 min in mean respectively. However, the diving period of medium sized bachelors was relatively short, from 3-23 min. The above periods were longer in comparison than with dives during critical conditions as when chased by commercial whalers. The whales swim at speeds of 0-6kt or 3kt in mean, and medium sized bachelors generally swim faster than large bachelors. The whales swim along an 18°C-isotherm of surface temperatner, and often along or across “Shiome.”