Marine mammals. Cetaceans

• The second group of marine mammals, which definitely rule the seas and complete their entire life cycle in the water, are the cetaceans, made up of whales and dolphins. The cetaceans remain in the water all the time and perform all their life's functions in the sea, including reproduction and rearing their young.
• In the cetaceans, the forelimbs exist solely in the form of flippers. Their finger bones are not elongated, as in the case of the pinnipeds, but they have more of them than land mammals (hyperphalangism).
• Instead of back limbs, they have a powerful tail for swimming, which propels the animal by moving up and down, clearly distinguishing them from fishes, which move their tail from side to side. Another characteristic shared by the majority of cetaceans is their dorsal fin, which helps them -along with their pectoral fins- to maintain their balance as they swim. Another characteristic typical of these mammals is that they have nasal orifices on the upper part of their head, which enables them to breath more efficiently when they break surface.
• The skin of the cetaceans is hairless. It is only in the baby or newborn whales that some vestiges of hair are still apparent. Instead of hair, they have a thick layer of fat under their skin, which provides them with an efficient system of insulation and an important reserve of energy, besides making it easier for them to float.

Return to hall 4