Archaeologists can tell a lot by looking through prehistoric trash. Piles of chipped stones and broken shells, crushed by hungry humans long ago, can reveal where we lived, how we lived, and for how long.

Now, scientists are applying this same archaeological approach to reveal new insights into a furry, endangered mammal with a similar taste for shelled snacks.

Wild sea otters habitually crack open mussels by smashing them on stationary stones, making them one of the few animals that use tools. By observing southern sea otters engaging in such behaviors along the California coast, and then analyzing wear and tear on stones and shells deposited nearby, researchers were able to make some surprising conclusions. (See what sea