They are mammals, they breathe air with lungs and can make a large gulp last up to an hour when plunging into the depths of the ocean. They give birth to live young which suckle milk. They are highly agile predators with a torpedo-shaped body, an elongated head with a bulging forehead, and a beaklike snout. They are renowned for their high intelligence, which enables them to home in on unsuspecting prey and communicate effectively with each other. They have a special waxy body in their swollen forehead known as a melon which focuses sound produced in the nasal passages and enables them to use echolocation to find prey such as squid and krill in deep, and often dark, waters.
Dolphins communicate with a variety of high-pitched squeaks, squeals and clicking sounds.
However, there are times when even dolphins need to sleep. Yet they still manage to remain in contact with one another. They do this by sleeping with one eye open. At the same time only one hemisphere of the dolphin's brain enters into slow wave or deep sleep mode. Patricia Goley from Humboldt State University, California, wanted to unravel the reason for this weird sleep pattern.