The behavior of sperm whales in schools observed from an operating whaler

A series of surveys on the swimming behavior of a sperm whale ,Physeter catodon, was undertaken on board a whaler of Ryuho Maru, 470 G/T, using an echo sounder in waters off Hachijo I. in 1979 and 1980. A method of the survey was based on the results of preliminary survey in january of 1979 and the second survey with a sounder and a visual survey with formal method were made in December of 1980. During the survey, a relative location of a whale was determined by polar system (The angular directions in vertical and horizontal plane, and range of the whale from the whaler) using a sounder. The geographic location was determined in referring the ship's location with Loran C per minute throughout the whale chasing duration. From the above data on 57 whales obtained during the survey, the swimming tracks of respective whales and cruising tracks of the whaler were drawn and time/dive showing depth profile of a whale were obtained. Based on the above resulted data and illustrations, many recent reports on the swimming behaviors were cited and several new knowlages are resulted. Under chasing condition, the whales were dived for a maximum of about 600m deep and their swimming speeds were ranged from 0-15 knots with an average of 6 knots. However, the high speed of 10 knots or more was not maintained for more than 2min. While, in the depth range of 0-600m, there is no significant defferences of the swimming speeds among various depth layers. The vertical component of the swimming speed of the whale is ranged from 0-2.5 knots with an average of 0.7±0.6 knot. Moreover, the whale quickly changes it swimming direction with the approach of the whaler. According to swimming track records, 30% of the data shows the whale swimming in a more or less straight course, while 63% of the data shows the whale ovaling turn less than 180°