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.

Otters are widely admired for their playful nature and energetic behaviour, but scientists and wildlife observers have also recognised them for something far more remarkable — their ability to use ...