Sea otters hold hands to sleep

Sea otters spend almost their whole lives floating on their backs at sea, and that brings a problem: while they sleep, the currents could carry them off in different directions. Their solution is the kind that melts hearts: they grip each other's paws and sleep holding hands, sometimes in groups of dozens forming rafts. Many also wrap themselves in kelp to stay anchored.

As if that weren't enough, they're one of the few species that use tools. To open clams and sea urchins, they set a rock on their chest and smash the shell against it over and over, as if against an anvil.

And they have a favourite rock: they keep it in a loose fold of skin under the forearm and carry it from place to place. Affectionate, handy, and with a pocket of their own.