North American river otters in Acadia National Park, Maine, USA

© George Sanker/Minden Picture

All going swimmingly. River otters in Maine, USA

These North American river otters are technically members of the weasel family and are not just locked into rivers. They can be found in waterways and along the coasts across North America – this pair are swimming in Acadia National Park in the US state of Maine - and have a tendency to come right up to humans or boats, usually within a few feet.

They’re active all year round, although they’re out and about mostly at night, hunting and eating. River otters are highly active predators, usually going after fish but they have been known to munch on fruit, reptiles, ducks and even the occasional beaver. River otters are highly sensitive to pollution, so will disappear from tainted areas.