The North American river otter (Lontra canadensis), also known as the northern river otter and river otter, is a semiaquatic mammal that only lives on the North American continent, along its waterways and coasts. An adult North American river otter can weigh between . The river otter is protected and insulated by a thick, water-repellent coat of fur.
The North American 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 North American river otters give birth in these 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 salamanders and frogs), freshwater clams, mussels, snails, small turtles and crayfish. The most common fish consumed are perch, suckers, and catfish. Occasional reports also show the river otter eating other small animals, such as mice, squirrels, birds, and even dogs that they've attacked and drowned.
The range of the North American river otter has been significantly reduced by habitat loss, beginning with the European colonization of the Americas. In some regions, though, their population is controlled to allow the trapping and harvesting of otters for their fur. North American river otters are very susceptible to the effects of environmental pollution, which is a likely factor in the continued decline of their numbers. A number of reintroduction projects have been initiated to help halt 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 North American river otter was first classified in the genus Lutra. Lutra was the early European name (from Latin), and the specific 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 (Pteronura brasiliensis) of South America 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 otter dating back 3.5 Mya (during the Pliocene) 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 New World river otters originated from the Old World river otters following a migration across the Bering Land Bridge, which existed off and on between 1.8 million and 10,000 years ago. This means they likely arrived in the Americas at a similar time as humans, meaning humans were an important part of their natural ecosystem from the moment otters arrived. The otters migrated to North America and southwards again across the Panamanian Land Bridge, which formed 3 Mya.
Subspecies
Listed alphabetically: L. c. canadensis (Schreber, 1777) – (eastern Canada, U.S., Newfoundland) L. c. kodiacensis (Goldman, 1935) – (Kodiak Island, Alaska) L. c. lataxina (Cuvier, 1823) – (U.S.) L. c. mira (Goldman, 1935) – (Alaska, British Columbia) L. c. pacifica (J. A. Allen, 1898) – (Alaska, Canada, northern U.S., south to central California, northern Nevada, and northeastern Utah) L. c. periclyzomae (Elliot, 1905) – (Queen Charlotte Islands, British Columbia) L. c. sonora (Rhoads, 1898) – (U.S., Mexico)
Description
The North American river otter has long whiskers that are used to detect prey in dark waters. An average adult male weighs about against the female's average of . Its body length ranges from . About one-third of the animal's total length consists of a long, tapered tail. Tail lengths range from . Large male North American river otters can exceed a weight of . It differs from the Eurasian otter by its longer neck, narrower visage, the smaller space between the ears and its shorter tail.