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The giant otter (''Pteronura brasiliensis'') is a South American carnivorous mammal. It is the longest member of the Mustelidae, or weasel family, a globally successful group of predators, reaching up to 1.7 m (5.6 ft). Atypical of mustelids, the giant otter is a social species, with family groups typically supporting three to eight members. The groups are centered on a dominant breeding pair and are extremely cohesive and cooperative. Although generally peaceful, the species is territorial, and aggression has been observed between groups. The giant otter is diurnal, being active exclusively during daylight hours. It is the noisiest otter species, and distinct vocalizations have been documented that indicate alarm, aggressiveness, and reassurance. The giant otter ranges across north-central South America; it lives mostly in and along the Amazon River and in the Pantanal. Its distribution has been greatly reduced and is now discontinuous. Decades of poaching for its velvety pelt, peaking in the 1950s and 1960s, considerably diminished population numbers. The species was listed as endangered in 1999 and wild population estimates are typically below 5,000. The Guianas are one of the last real strongholds for the species, which also enjoys modest numbers — and significant protection — in the Peruvian Amazonian basin. It is one of the most endangered mammal species in the neotropics. Habitat degradation and loss is the greatest current threat. The giant otter is also rare in captivity; in 2003, only 60 animals were being held. The giant otter shows a variety of adaptations suitable to an amphibious lifestyle, including exceptionally dense fur, a wing-like tail, and webbed feet. The species prefers freshwater rivers and streams, which are usually seasonally flooded, and may also take to freshwater lakes and springs. It constructs extensive campsites close to feeding areas, clearing large amounts of vegetation. The giant otter largely subsists on a diet of fish, particularly characins and catfish, and may also eat crabs, small snakes and small caiman.〔Groenendijk, J., Hajek, F. & Schenck, C. 2004. Pteronura brasiliensis. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. (http://www.iucnredlist.org/search/details.php/18711/all)〕 It has no serious natural predators other than humans, although it must compete with other species, including the neotropical otter and caiman species, for food resources. == Naming == The giant otter has a handful of other names. In Brazil it is known as ''ariranha'', from the Tupí word ''ari'raña'', meaning water jaguar ((ポルトガル語:onça d'água)). In Spanish, river wolf ((スペイン語:lobo de río)) and water dog ((スペイン語:perro de agua)) are used occasionally, though the latter has many other meanings) and may have been more common in the reports of explorers in the 19th and early 20th centuries.〔See e.g., 〕 All three names are in use in South America, with a number of regional variations. "Giant otter" translates literally as ''nutria gigante'' and ''lontra gigante'' in Spanish and Portuguese, respectively. Among the Achuar people, they are known as ''wankanim'',〔 and among the Sanumá as ''hadami''. The genus name, ''Pteronura'', is derived from the Ancient Greek words ''pteron''/πτερον (feather or wing) and ''ura''/ουρά (tail), a reference to its distinctive, wing-like tail.〔 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「giant otter」の詳細全文を読む スポンサード リンク
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