California sea lion (English name: Zalophus californianus)

Japanese: カリフォルニアアシカ（英語表記）Zalophus californianus; California sea lion

Order Carnivora, Suborder Pinnipedia, Family Otariidae, Genus Otariidae. Also called the black sea lion. Males can reach a body length of about 2.4m and females about 2m, and males weigh more than 390kg and females about 110kg. Newborn young are about 80cm long and weigh 6-9kg. Body color is dark brown, females are slightly lighter and closer to yellowish brown. Body color darkens from the chest to the abdomen, and the limbs are dark blackish brown. Body shape is spindle-shaped. The limbs are bare and hairless from the tip to the base, fin-like, and the forelimbs have degenerated claws. The snout is short and rounded at the tip, and the ears are relatively small. The muzzle is elongated and slightly concave in the center of the top of the head. When males reach sexual maturity, a mane-like, slightly long hair grows on the neck and a hump-like protuberance appears on the forehead. There are six incisors in the upper jaw and four in the lower jaw, two canines each in the upper and lower jaw, and ten cheek teeth each in the upper and lower jaw. The breeding season is from May to July, and after the breeding season, most males, subadults, and immatures migrate from their breeding grounds to northern waters. They are polygamous, with one male forming a group of about 15 females. They are active and sometimes swim by jumping like dolphins. They feed on squids, octopuses, and fish, and often steal the catches of fishermen and anglers. They are distributed from central Mexico to northern British Columbia, including the Gulf of California, and appear from the coast to the continental shelf. They are often kept in captivity and trained. The subspecies, the Galapagos sea lion Zcwollebaeki , is found only around the Galapagos Islands and is slightly smaller than this species, with males weighing about 200 kg and females weighing 50 to 100 kg. The Japanese sea lion (Zcjaponicus) , a subspecies found in the western Pacific Ocean, has not been seen since 1974 and is listed as extinct on the International Union for Conservation of Nature (IUCN) Red List (→Red Data Book) and as endangered on the Ministry of the Environment Red List.

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

Japanese:

食肉目鰭脚亜目アシカ科アシカ属。クロアシカともいう。体長は雄約 2.4m，雌約 2mに達し，体重は雄約 390kg以上，雌約 110kgである。出生直後の幼獣は体長約 80cm，体重は 6～9kgである。体色は茶褐色で，雌の方がやや淡く黄褐色に近い。胸部から腹部にかけて体色が濃くなり，四肢は濃黒褐色である。体型は紡錘形。四肢は裸出し先端から基部にいたるまで毛は生えず，鰭（ひれ）状で前肢には退化した爪がみられる。吻は短く先端は丸みを帯び，耳介は比較的小さい。鼻口部は細長く，頭頂部の中央がややくぼむ。雄は性的成熟に達すると首にたてがみ状のやや長い毛が生え，前頭部にこぶ状の隆起ができる。門歯は上顎 6本，下顎 4本，犬歯は上顎と下顎に 2本ずつ，頬歯は上顎と下顎に各 10本である。繁殖期は 5～7月で，繁殖期を過ぎると，ほとんどの雄と亜成獣および未成獣は，繁殖場から北方水域へ回遊する。一夫多妻で 1頭の雄に 15頭程度の雌で群れをつくる。活動的でイルカのようにジャンプしながら泳ぐこともある。スルメイカ類，タコ類および魚類を食べ，漁師や釣人の獲物を横取りすることが多い。カリフォルニア湾を含み，メキシコ中部からブリティシュコロンビア州北部に分布し，沿岸部から大陸棚に出現する。飼育や調教がよく行なわれている。亜種であるガラパゴスアシカ Z.c.wollebaekiはガラパゴス諸島周辺に限定分布し，本種よりやや小さく，雄の体重は約 200kg，雌の体重は 50～100kgである。太平洋西部に分布していた亜種のニホンアシカ Z.c.japonicusは 1974年以降目撃されておらず，国際自然保護連合 IUCNのレッドリスト（→レッドデータブック）では絶滅種に，環境省のレッドリストでは絶滅危惧種に指定されている。

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