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Cetacean stranding is a phenomenon in which cetaceans strand themselves on land, usually on a beach. Beached whales often die due to dehydration, collapsing under their own weight, or drowning when high tide covers the blowhole. Several explanations of the stranding have been proposed. ==Species== Every year, up to 2,000 animals beach themselves.〔 〕 Although the majority of strandings result in death, they pose no threat to any species as a whole. Only about 10 cetacean species frequently display mass beachings, with 10 more rarely doing so. All frequently involved species are toothed whales (Odontoceti), rather than baleen whales (Mysticeti). These species share some characteristics which may explain why they beach. Body size does not normally affect the frequency, but both the animals' normal habitat and social organization do appear to influence their chances of coming ashore in large numbers. Odontocetes that normally inhabit deep waters and live in large, tightly knit groups are the most susceptible. This includes the sperm whale, oceanic dolphins, usually pilot and killer whales, and a few beaked whale species. Solitary species naturally do not strand en masse. Cetaceans that spend most of their time in shallow, coastal waters almost never mass strand. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cetacean stranding」の詳細全文を読む スポンサード リンク
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