Which animal do you reckon is the cleverest of the lot?

Dogs can learn hundreds of words and read your mood from across the room. Some collies can fetch a named toy from a pile of thirty.

Crows bend wire into hooks to fish food out of tubes, and they remember faces of people who annoyed them. They've even been spotted dropping nuts in traffic so cars crack them open.

An octopus can undo a lid from the inside to get at a crab. Aquarium staff swear they squirt water at the keepers they don't like.

Pigs can work a joystick game with their snouts and learn their own name in days. They're also spotless if you give them the space.

Dolphins call each other by whistled names and team up to herd fish into a circle. They also seem to muck about purely for fun.