Whales

Whales (also called libiri) are a general term for a group of fully aquatic marine mammals. This group includes large whales, dolphins, and various smaller species. In Somali, the word "nibiri" is commonly used to refer to large whales of the sea.

Although whales resemble fish in appearance, they are not fish. They are mammals: they give birth to live young, nurse them with milk, breathe through a blowhole, and take air from above the water surface. For this reason, they must regularly surface to breathe.

Body structure

The whale body has a streamlined shape that moves through water easily. The front flippers are modified limbs (with arm-like bones), while the hind limbs have disappeared. The tail has two horizontal flukes that move up and down, unlike fish whose tails move side to side. On top of the head lie one or two blowholes through which air enters.

Divisions of the group

Scientists divide whales into two major groups. The first group has teeth and includes dolphins, orcas, and toothed whales. The second group has no teeth but instead has baleen (a tooth-like substance used to filter small animals from water), which it uses to strain tiny organisms from the sea. The largest animals in the world belong to this second group.

Feeding and behaviour

Baleen whales generally feed on small organisms in schools, taking in large amounts of water and then filtering it out. Toothed whales hunt fish, squid, and sometimes other marine mammals. Dolphins and many other whales use natural sonar: they produce sounds and listen to the echoes that return, allowing them to locate prey.

Habitat and conservation status

Whales are found in oceans worldwide, from cold polar waters to warm tropical seas. Many species undertake long migrations between feeding and breeding grounds. Large-scale commercial whaling in the nineteenth and twentieth centuries drastically reduced populations of many species; international agreements that limited whaling were subsequently established. Current threats include fishing net entanglement, ship strikes, pollution, and climate change.