Aquatic mammals are specially adapted animals that live totally or partially in the water. They are found in either marine or fresh water. Some, like manatees, can live in both. As mammals, they all breathe air, nurse their young, have backbones, body hair at some stage of their development, and warm blood. Sirenians are unique because they are the only aquatic mammals that feed exclusively on plants. Aquatic mammals are highly adapted to live in aquatic environments. Their streamlined bodies facilitate swimming; some have layers of fat, or blubber, to provide insulation against low water temperatures; and other adaptations help them to see, breathe, and navigate in the water. Though aquatic mammals have much in common because of their physical structure and aquatic habitat, each is adapted to its own particular lifestyle and niche. Aquatic mammals that live in cold areas or deep water have developed better insulation than the manatee requires in its tropical home. Predators or carnivores such as the polar bear and killer whale must have speed, strength, and weapons such as sharp, biting teeth or claws to catch and kill prey. The manatees' vegetarian diet requires grinding molars, and less proficient swimming ability. Sirenians, and cetaceans (whales and dolphins) never leave the water during their lifetime. Calves are born and nursed in water and breeding, resting, and feeding are all done in the water. They surface to breathe air. Some aquatic mammals - seals and polar bears for instance - go ashore to breed and raise their young, returning to the ocean to feed. Many whales must dive to great depths to find food, so their breath-holding capacity must be greater. The manatees' shallow water diet does to require this skill. Even though all aquatic mammals share some common characteristics and problems, each is unique and occupies a special niche in the aquatic environment.

Activities Compare and contrast the manatee with another aquatic mammal. Discuss food and feeding habits, temperature and depth preference, speed, physical characteristics and adaptations, breeding, habitat, climate, and other interesting details. Using the species pictured on the next web page (The Great Mammal Match-Up), discuss how each animal is suited to its habitat. how is it adapted to find food? Identify the carnivores, omnivores, and herbivores. Compare manatees to humans. What special equipment must people use to move comfortably underwater? How is a manatee better suited to an aquatic life? Why do people have hands and manatees have flippers? How does the manatee's shape help it move through the water? Compare the manatee (a mammal) to other aquatic animals of different vertebrate classes. The sea turtle (reptile), shark (fish), and penguin (bird) share some important characteristics, but are also different in many ways. Compare how each is adapted to its particular lifestyle. Stress the uniqueness and variety of nature as evidenced by the variety within the aquatic mammal grouping. Let students try to think of ways manatees could be better adapted to their habitat. Many aquatic mammals are hunted commercially for their meat, blubber, or fur. Have students research one of these animals and find out how hunting pressures have affected the population. Is the species considered endangered? Is it protected? There are specific laws (see It's the Law ...) that protect aquatic mammals. Find out about them. Discuss the word "stranding" and "beaching" and how it relates to aquatic mammals (e.g. whales, porpoises). Have students research the current theories on why some aquatic mammals strand themselves. Could this happen to the manatee? Why can manatees live a relatively solitary life when other animals, including people, need the protection or company of a group? Which other animals live in groups and why? Pick 10 animals of different species and find out what term is used for male, female, and young. For manatees, it is bull, cow, and calf. Find out what the gestation period is for other mammals such as elephants, whales, humans, or cats. How old are individuals before they produce young?

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