|
|infraordo = Cetacea |subdivision_ranks = Subgroups | subdivision = * Parvorder * *Mysticeti * *Odontoceti }} The cetaceans are marine mammals, characterised by having a fusiform body, paddle-shaped front limbs and vestigial hind limbs. Their tails have been flattened into flukes to aid propulsion. The cetaceans are included in the order Cetartiodactyla with the Artiodactyla (the even-toed ungulates). Previously, they were all within their own order, Cetacea with Suborders Odontoceti and Mysticeti, but they are currently divided into two unranked taxa, the Odontoceti (the toothed whales, including dolphins and porpoises) and the Mysticeti (the baleen whales). There are 90 living species of cetaceans (including the functionally extinct Yangtze dolphin). In addition, numerous species of extinct cetaceans have been documented, but they are not listed here. This list contains only the known, extant cetacean species including several recent newly defined species. Cetaceans are widespread, but some, as with the mysticetes, specialize in certain environments. Most mysticetes prefer the colder waters of the Northern and Southern Hemispheres, and migrate to the equator to give birth. Odontocetes feed largely on fish and squid, but a few, like the killer whale, feed on mammals, such as pinnipeds. Grey whales are specialized for feeding on bottom-dwelling mollusks. Males typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively long period of time. Some whales produce a variety of vocalizations, notably the songs of the humpback whale. Many species, mainly dolphins, are highly sociable, with some pods reaching over a thousand individuals. Once relentlessly hunted for their products, whales are now protected by international law. Some species are attributed with high levels of intelligence. At the 2012 meeting of the American Association for the Advancement of Science, support was reiterated for a cetacean bill of rights, listing cetaceans as non-human persons. The North Atlantic right whales nearly became extinct in the twentieth century, with a population low of 450, and is considered functionally extinct by cetologists, and the Baiji is also considered functionally extinct by the IUCN with the last sighting in 2004. Besides whaling, they also face threats from bycatch and marine pollution. The meat, blubber and baleen of whales have traditionally been used by indigenous peoples of the Arctic. Whales occasionally feature in literature and film, as in the great white whale of Herman Melville's ''Moby Dick''. Small cetaceans, mainly dolphins, are kept in captivity and trained to perform tricks, but breeding success has been poor. Whale watching has become a form of tourism around the world. ==Conventions== 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「List of cetaceans」の詳細全文を読む スポンサード リンク
|