At least 25 species have been recorded around Britain, and they make up one quarter of all British mammal species. Cetaceans have a streamlined, torpedo-shaped body to allow movement through water with the minimum of resistance. They have no hind limbs and their forelimbs are modified to form flippers, used to balance and steer. When diving, a cetacean holds its breath and compresses its elastic lungs. The lungs expand again whilst returning to the surface and the used air is forced out through the blowholes, appearing as a cloud of spray.
Whales feed in one of two ways.
This group includes the sperm whale and orca or killer whale as well as the dolphins and porpoises. These plates are made from keratin, a hard material that also makes our fingernails. The whales strain seawater between the plates to extract small animals called plankton and, for some species, fish and squid. The minke and humpback are both baleen whales, as is the blue whale, the largest living animal. Whales and dolphins around the British Isles Eleven species of cetaceans are regularly recorded in British and Irish waters.