The North American river otter (Lontra canadensis) is a member of the weasel family widely distributed along coasts, lakes, and other waterside habitats in Canada and the United States. It feeds mainly on fish and is adapted for swimming with a streamlined body with webbed feet and dense, oily fur. Dens make use of beaver construction or tree cavities, and those with underwater entrances are used for rearing young. Social organization varies, including mother-offspring groups, solitary males, and pairs, and they engage in complex communication through scent, vocalizations, and grooming. Mating occurs in winter and, due to delayed implantation, birth takes place about one year after mating. Populations have recovered through conservation measures and are currently assessed as Least Concern.