False killer whale (English name: Pseudorca crassidens; false killer whale)

Japanese: オキゴンドウ（英語表記）Pseudorca crassidens; false killer whale

It is a member of the genus False Killer Whale, of the family Delphinidae, suborder Odontoceti, order Cetacea. Males reach a body length of about 6m, and females about 5m. Large males can weigh nearly 2t. Their birth length is 1.5-2.1m. Their body color is blackish-gray or black all over, with pale gray spots on their chest. Their body shape is the most slender of all pilot whales. They have one blowhole located on the midline of their head. Their upper jaw protrudes beyond their lower jaw, and although they have no beak, their snout is pointed. Their dorsal fin is located almost in the center of their body, with a blunt and somewhat small tip. In sexually mature males, the tip of their dorsal fin hangs backward, and the rear edge is deeply curved. Their pectoral fins bend backwards sharply near the center, and are pointed at the tip. They have 7-12 pairs of large conical teeth on the upper and lower jaws, which enable them to bite and tear apart prey. They usually live in groups of 10-60 individuals, but can form large groups of several hundred. They are known to drift ashore in large numbers. They are capable of high-speed swimming. They mainly prey on fish and squid, but occasionally attack whales. They are found in the deep oceans of tropical and temperate waters, and can be found between 50° north and 50° south latitude. In Japan, they are caught by drive fishing. It is thought that most damage caused to tuna longlines is caused by this species.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

クジラ目ハクジラ亜目マイルカ科オキゴンドウ属。体長は雄約 6m，雌約 5m。大型の雄は体重約 2t近くになる。出生体長は 1.5～2.1m。体色は全身黒灰色あるいは黒色で，胸部に淡い灰色の斑を呈する。体型はゴンドウクジラ類中最も細長い。噴気孔は1個で頭部正中線上に位置する。上顎は下顎より突き出ており，嘴 (くちばし) はないが吻端はとがる。背鰭 (せびれ) はほぼ体の中央に位置し，先端は鈍くやや小さい。性的成熟に達した雄の背鰭は先端が後方に垂れ，後縁が深く湾曲している。胸鰭は中央付近で急に後方へ曲り，先端はとがる。上下顎骨に大きい円錐歯が左右7～12対並び，餌を噛み，引裂くことができる。通常 10～60頭程度の群れで行動するが，数百頭の大群をなすこともある。大量漂着する種として知られている。高速遊泳が可能である。おもに魚類やイカ類を捕食するが，まれにクジラ類を襲う。熱帯から温帯海域の深海外洋域に分布し，北緯 50゜から南緯 50゜までに出現する。日本では追込漁によって捕獲される。マグロ延縄の食害のほとんどは本種によると考えられている。

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