Whales, dolphins and porpoises make up a group of mammals called cetaceans. These animals live in the waters of the oceans all the time. They have no hair or fur on their bodies. Instead of four legs, they have a tail, called a fluke, and two flippers. Under their skins they have a thick layer of fat called blubber to keep them warm in cold waters. As air-breathing mammals, whales have to come to the surface of the water to breathe air. They breathe through the holes on top of their heads called blowholes. They have excellent hearing, but a poor sense of smell.

Whales are the largest animals in the world. In fact, the enormous blue whale, which can measure over 30 metres (100 feet) long, is probably the biggest animal that has ever lived. Whales are able to grow so large because their huge weight is supported by the water. If a land animal grew to this size, its legs would collapse under the weight of its own body. There are two types of whale: baleen whales and toothed whales.

Some whales have many small, peg-like teeth. The group includes the sperm whale, beluga, narwhal and the beaked whales. These whales feed mainly on fish or squid. The sperm whale preys on giant squid. Despite their names, the killer whale and pilot whale are considered to be dolphins rather than whales.

Dolphins

Dolphins, like whales, live permanently in the water. All dolphins have teeth. Most live in the ocean, but some live in rivers. Many dolphins live in groups called pods, which usually stay together for life. Highly intelligent animals, they have good eyesight and exceptional hearing. They call to each other using squeaks and clicks. They hunt fish and squid near the water’s surface. The pod hunt fish by working together to round them up.