The adorable, whimsical antics of otters make them favorites at zoos and aquariums around the world. In case you're lucky enough to see an otter frolicking in the wild, follow this advice to distinguish a sea otter from its river cousin.
See how it swims. Watching how an otter behaves in water is an easy way to distinguish between a river otter and a sea otter. River otters swim belly-down with only a little of their backs popping up above the surface. Sea otters, on the other hand, swim belly-up and tend to float high in the water.
Look at how the otter moves on land. River otters frequently travel between water to their dens on land without a problem. Sea otters are true ocean-dwelling marine mammals. They don't leave the water often and move around clumsily when they do.
Peek at their paws. River otters have webbed hind paws that are smaller and more circular than the paws of their sea otter cousins. Sea otters have paws webbed all the way to the tips of their toes. Their longest toe is on the outside to aid in swimming, but makes for slow going on land.
Watch what's for dinner. Though both river and sea otters eat the standard fish, snails and clams, sea otters also have a taste for things like crabs and sea urchins.
Survey where they sleep. River otters play in the water by day, but at night return to their dens on land to sleep. Sea otters sleep right in the water where they swim.