As humans, we want to believe that we're the smartest creatures on the planet. But the more we understand octopuses, the more it seems that we may not be alone in our ability to solve problems, make complex connections between ideas, and survive by wits alone. A growing body of evidence suggests that octopuses show elements of intelligence. Their intelligence has evolved for very different reasons than ours did, which makes them particularly difficult to understand.
So, why is the octopus so intelligent? What is its mind for? Due to the ease with which these soft creatures could be eaten, only the smartest octopuses would survive, i.e. the ones who could hide the most cunningly using their environment to avoid being eaten. It's becoming clear that octopuses use tools such as coconut shells to hide. Octopuses have even been observed in the wild gathering stones to hide the entrance to their dens. In captivity they tend to play with anything they can get their tentacles on and demonstrate a great deal of curiosity. Robot submarines put into their tanks have been taken apart and an octopus at an aquarium in California even emptied its tank by dismantling a valve.
Further, they have been known to climb out of bed tanks at night, eat fish from a neighbouring tank and return to their home leaving the aquarium attendance wondering where their fish had disappeared to.