Why do sea otters use rocks?

Answer: Cracking open shellfish

Cracking open shellfish ✓ — Correct! Sea otters are one of the few tool-using animals! They dive for clams, sea urchins, and mussels, then float on their backs using their chest as an 'anvil.' They pound the shells against a rock until they crack open. Some otters have favorite rocks they keep in their armpit skin folds!

Anchoring themselves while sleeping — Wrong. Sea otters do wrap themselves in kelp to avoid drifting, but rocks are primarily tools for cracking shells, not anchors.

Playing games together — Wrong. While otters are playful, rock use is serious business—it's a learned hunting skill passed from mother to pup for accessing hard-shelled food.