John Cancalosi / River otter (Lutra canadensis) grooming and settling to rest, Wyoming, USA, July.

John Cancalosi / River otter (Lutra canadensis) feeding on Cutthroat trout (Oncorhynchus clarkii), Wyoming, USA, July.

John Cancalosi / River otter (Lutra canadensis) feeding on Cutthroat trout (Oncorhynchus clarkii), Wyoming, USA, July.

George Sanker / North American river otter (Lontra canadensis) emerging from water, Acadia National Park, Maine, USA, October.

Roger Powell / North American river otters (Lontra canadensis) family group with one of which has just caught a crab, Lower Suwannee River, Levy County, Florida, USA April

Will Burrard-Lucas / North American river otter (Lontra canadensis), group exploring the banks of river. Grand Teton National Park, USA. May

Edwin Giesbers / North American river otter (Lutra canadensis) captive, occurs in North America.

Paul Hobson / North American river otter (Lontra canadensis) playing in snow, Yellowstone National Park, Wyoming, USA, February.

Paul Hobson / North American river otter (Lontra canadensis) playing in snow, Yellowstone National Park, Wyoming, USA, February.

Paul Hobson / North American river otter (Lontra canadensis) playing in snow, Yellowstone National Park, Wyoming, USA, February.

Paul Hobson / North American river otter (Lontra canadensis) playing in snow, Yellowstone National Park, Wyoming, USA, February.