Today, power plant outfalls and other warm-water discharges are important winter destinations for many manatees. These artificially heated sources have allowed manatees to remain north of their historic wintering grounds. Population studies on Antillean, Amazonian, and West African manatees are inadequate to determine reliable population numbers. Populations of all species of manatees have apparently declined over the past hundred years. Manatees are one of the most endangered marine mammals. To add to their problems, manatees have a very slow reproductive cycle. Cows give birth only once every 3 to 5 years. People are the major threat to manatees. Manatees are slow, non- aggressive animals which makes them easy to hunt. Their large bodies have a lot of meat so a single animal can feed a large family for a long time. In the United States, hunting is not the major problem, but habitat is. A quiet water habitat that can provide 100 pounds of water plants per day per manatee is key to their survival.
Manatees are mammals that live in warm fresh water and seawater. They belong to the group or Order Sirenia which includes both manatees and dugongs. The five species or types of animals in this order include the West Indian manatee, West African manatee, Amazonian manatee, dugong, and Steller's sea cow. Unfortunately, the Steller's sea cow is extinct. Manatees rely on a strictly vegetarian diet of algae and other marine plants. Like proboscideans to which they are believed related, manatees replace their anterior molariform teeth through the addition of posterior teeth. They have been reported to take dead fish from nets and to eat dead fish in captivity and presumably consume substantial quantities of arthropods associated with ingested vegetation. Scientists now know that manatees are more closely related to elephants than any other living animal. Scientists believe that manatees evolved from land mammals that returned to an aquatic life. Manatees are the only marine mammals that are herbivores. The first recorded observations of manatees date back to Columbus' expedition in 1492. Even so, nearly everything we know about manatees has been learned in the last 25 years.