Sea otters use tools, too. Now scientists look at their 'archaeology'

A Eurasian river otter mother relaxes with with her two seven-month-old cubs on a shoreline in Shetland, U.K.

Giant river otters like these in Ecuador are born covered with fur.

River otters tend to live alone, but they socialise in playful groups.

Sea otters sometimes link feet to hold each other in what's called a raft—a group of sea otters in the water.

A Eurasian river otter family plays on a shore covered in seaweed.