CNN — When sea otters hammer mussel shells against rocks to help open them, they're leaving behind their own archaeological record that can't be compared to any other creature, according to a new ...

Add Yahoo as a preferred source to see more of our stories on Google. Sea otters are highly intelligent marine creatures. Their intelligence is shown by their inquisitiveness and their use of tools.

Credit: flickr Sea otters are one of the few non-human species known to use tools. They often carry small rocks to crack open hard shells like clams, crabs, or mussels. This behavior demonstrates ...