Brain of a female common dolphin

Dolphins have a long history of interaction with humans and are renowned for their intelligence. They show a remarkable ability to learn, communicate, and form concepts and cultures. However, much of the brain mass of large mammals may be devoted to sensation and movement rather than cognition. Some theorists relate mammalian intelligence to numbers of cortical neurons, and bottlenose dolphins are estimated to possess just over half as many of these (5.8 billion) as humans – between chimpanzees and gorillas but fewer then elephants.