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The North American river otter (''Lontra canadensis''), also known as the northern river otter or the common otter, is a semiaquatic mammal endemic to the North American continent found in and along its waterways and coasts. An adult river otter can weigh between . The river otter is protected and insulated by a thick, water-repellent coat of fur. The river otter, a member of the subfamily Lutrinae in the weasel family (Mustelidae), is equally versatile in the water and on land. It establishes a burrow close to the water's edge in river, lake, swamp, coastal shoreline, tidal flat, or estuary ecosystems. The den typically has many tunnel openings, one of which generally allows the otter to enter and exit the body of water. Female otters give birth in these underground burrows, producing litters of one to six young. North American river otters, like most predators, prey upon the most readily accessible species. Fish is a favored food among the otters, but they also consume various amphibians (such as frogs〔"(otter )". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2014. Web. Retrieved 20 Jan. 2014〕), turtles, and crayfish. Instances of river otters eating small mammals and occasionally birds have been reported as well. The range of the North American river otter has been significantly reduced by habitat loss, beginning with the European colonization of North America. In some regions, though, their population is controlled to allow the trapping and harvesting of otters for their pelts. River otters are very susceptible to environmental pollution, which is a likely factor in the continued decline of their numbers. A number of reintroduction projects have been initiated to help stabilize the reduction in the overall population. ==Taxonomy and evolution== The North American river otter was first described by German naturalist Johann Christian Daniel von Schreber in 1777. The mammal was identified as a species of otter and has a variety of common names, including North American river otter, northern river otter, common otter and, simply, river otter.〔 Other documented common names are American otter, Canada otter, Canadian otter, fish otter, land otter, nearctic river otter, and Prince of Wales otter. The river otter was first classified in the genus ''Lutra''; ''Lutra'' was the early European name. The species name was ''Lutra canadensis''.〔 The species epithet ''canadensis'' means "of Canada". In a new classification, the species is called ''Lontra canadensis'', where the genus ''Lontra'' includes all the New World river otters. Molecular biological techniques have been used to determine when the river otter and the giant otter diverged. These analyses suggest they diverged in the Miocene epoch 23.03 to 5.33 million years ago (Mya), which is "much earlier" than indicated in the fossil record. Fossils of a giant river otter dating back 3.5 Mya have been found in the US Midwest, however fossils of the modern river otter did not appear in North America until about 1.9 Mya. The earliest known fossil of ''Lontra canadensis'', found in the US Midwest, is from the Irvingtonian stage (1,800,000 to 300,000 years ago). The oldest fossil record of an Old World river otter comes from the late Pliocene epoch (3.6 to 1.8 Mya). The New World river otters originated from the Old World river otters after a migration across the Bering Land Bridge, which existed off and on between 1.8 million and 10,000 years ago. The otters migrated to North America and southwards again across the Panamanian Land Bridge, which formed 3 Mya.〔 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「North American river otter」の詳細全文を読む スポンサード リンク
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