南半球における小型歯鯨類の観察記録

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Eight species of Delphinidae (Orcinus orca, Lagenorhynchus cruciger, Lagenorhynchus obscurus, Globicephala melaena, Delphinus delphis, Stenella coeruleoalba, Lissodelphis peronii, and Grampus griseus) and two species of Ziphiidae (Berardius arnuxii and Hyperoodon planifrons) were sighted during the minke whale assessment cruises in the Southern Hemisphere for three seasons, 1978/79,1979/80 and 1980/81. Geographical distribution, relative density, school size, surface water temperature at sightings and characteristic behavior of the above ten species were examined in the present study. Killer whales and beaked whales were concentratedly sighted along the ice edge of 60-70°S and in the Ross Sea. Apparent segregation between killer whales and beaked whales were observed in their overlapped areas, and the former whales showed higher density in the Ross Sea than the latter. Both long-finned pilot whales and hourglass dolphins were sighted in the north and south of the Antarctic Convergence like killer whales and beaked whales. On the other hand, other five delphinid species were found only in the north of the Antarctic Convergence. Most of beaked whales (71.5%) were sighted in solitary or pair, although delphinid species were composed of relatively larger school of several animals to about one thousand animals. Seven types of multi-species combination were observed as follows : 1) killer whales and minke whales, 2) long-finned pilot whales and minke whales, 3) long-finned pilot whales and southern right whale dolphins, 4) beaked whales and minke whales, 5) hourglass dolphins and fin whales, 6) killer whales and humpback whales, 7) longfinned pilot whales, southern right whale dolphins and hourglass dolphins.
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南半球における小型歯鯨類の観察記録

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