White whale (English spelling) Delphinapterus leucas; white whale

Japanese: シロイルカ（英語表記）Delphinapterus leucas; white whale

Beluga whales are part of the order Cetacea, suborder Odontoceti, family Narhalidae, and genus Beluga. They are also known as the canaries of the sea because of their high-pitched cry. Males are up to 5.5m long, and females up to 4.1m long. They can reach a maximum weight of 1.6t. Their birth length is about 1.6m. Their body color changes with age. Young whales are indigo-gray with dark, fine markings, but the markings later turn grayish yellow, and by the time they reach sexual maturity, their entire bodies are white. Adult whales are a whitish ivory color. They have a round head and a large mouth. They have no beak. Their neck is distinct, and the cervical vertebrae are free, so they can swing their head from side to side. They have one blowhole, located on the midline of their head. It has no dorsal fin, but a protuberance of about 1m in length in the center of its back, and a keel (ridge) toward the center of its caudal fin. Its pectoral fin is fan-shaped and rounded. It has 8-10 pairs of teeth, each about 8mm in diameter. It usually lives in schools of about 15 individuals, but sometimes it can form schools of more than 100 individuals. It usually moves slowly, but in summer it gathers at the mouth of a river and becomes active. It breeds from April to August. It mainly eats bottom-dwelling fish, but also preys on large crustaceans such as squid and snow crab. It is widely distributed in the Arctic and subarctic regions. It lives on the coast, but sometimes appears in the open ocean and at river mouths. Its skin is of high quality and is used for shoes and book spines. Whale oil from this species is very expensive. In the Arctic, its meat and blubber are valuable foods. There are concerns about the impact that the development of oil and natural gas resources will have on the ecosystem.

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

Japanese:

クジラ目ハクジラ亜目イッカク科シロイルカ属。別称ベルーガ。かん高い鳴き声を発することから海のカナリアとも称される。体長は雄約 5.5m以下，雌約 4.1m以下。体重は最大約 1.6tに達する。出生体長は約 1.6m。体色は年齢とともに変化する。幼鯨は藍ねずみ色で濃く細かい斑紋があるが，のち斑紋は灰黄色となり，性的成熟に達する頃には全身白色となる。成鯨は白っぽい象牙色。頭部は丸く口は大きい。嘴 (くちばし) はない。頸部は明瞭で，頸椎骨が遊離しているので頭部を左右に振ることができる。噴気孔は1個で頭部正中線上にある。背鰭 (せびれ) はないが，背部中央に長さ約 1mの隆起があり，尾鰭中央に向ってキール (稜線) をなす。胸鰭はうちわ状で丸い。歯は上下ともに左右8～10対あり，歯の直径は 8mm程度。 15頭前後の群れをなすことが多いが，ときおり 100頭以上の群れをなす。通常動きは緩慢であるが，夏季は河口に集り活発に行動する。繁殖期は4～8月。おもに底生魚類を食するが，イカ類やズワイガニ等の大型甲殻類も捕食する。北極圏と亜北極域に広く分布する。沿岸に生息するがときには外洋や河口にも出現する。皮は上質で靴や書物の背表紙に使われる。本種の鯨油は非常に高価である。北極地方では肉や脂皮が食料として貴重。石油や天然ガス資源の開発によって生態に及ぼされる影響が懸念されている。

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