Marine mammals are animals that make their home in or near the ocean. All marine mammals have a backbone. Marine mammals give birth to live young. Marine mammals feed off milk when they are young. All marine mammals have some form of hair. They are warm-blooded and must breathe air. Marine mammals have adaptations such as fur or blubber that help them maintain their body temperature.
There are about one hundred and twenty species of marine mammals. Only the polar bear and the sea otter have legs. The rest use fins or flippers for movement in the water and on land.
Marine mammals are divided into five groups. The Sirenia group includes the dugong and manatee. The Cetacea group includes whales, dolphins, and porpoises. This is the largest group. There are over seventy species in this group.