All living sirenians are found in warm tropical and subtropical waters (Nowak and Paradiso, 1983).
The West Indian manatee was once abundant throughout the tropic and subtropical western North and South Atlantic and Caribbean waters. However, the manatee's numbers have been greatly reduced. Today, the West Indian manatee is listed as an endangered species throughout its range.
The range of the Florida manatee is primarily peninsular Florida but extends as far north as Rhode Island. Manatees have been rescued near Houston, Texas, and Mississippi.
Antillean manatees have a patchy distribution throughout the Caribbean, Mexico, and northeastern South America. The southern range extends through Central and South America to Brazil.
West African manatees range from Senegal to Angola, on the west coast of Africa.
Amazonian manatees are the only species of manatee confined to fresh water. They inhabit the Amazon Basin, mostly in Brazil. They are uncommon or close to extinction in Peru, Ecuador, and Colombia
Habitat
The West Indian and West African manatees inhabit rivers, bays, canals, estuaries, and coastal areas rich in seagrass and other vegetation. They can live in fresh, saline (salt), and brackish waters. They move freely between extremes.
West Indian manatees may be found in any waterway over 1 m (3.25 ft.) deep and connected to the coast. They prefer waters with temperatures above 21°C (70°F). Florida manatees rarely venture into deep ocean waters. However, manatees have been spotted as far offshore as the Dry Tortugas Islands, approximately 81 km (50 mi.) west of Key West, Florida.
West African manatees live in quiet coastal areas, large rivers, lagoons, and connected lakes, where the water temperature is above 18°C (64°F).
The Amazonian manatee is restricted to fresh water. They are most common in floodplain lakes and channels in white-water river systems with water temperatures ranging from 25°-30°C (77°-86°F).
The patchy distribution of manatees throughout all their ranges is due to their search of suitable habitat: plentiful aquatic plants and a freshwater source of water to drink.
Migration
Florida manatees move into warmer waters when the water temperature drops below about 20°C (68°F).
Historically, Florida manatees have migrated south into warmer waters during the colder months of the year. On the Gulf coast, manatees congregated at natural warm-water springs. On the Atlantic coast, manatees headed south of the Sebastian River.
Today, power plant outfalls and other warm-water discharges are important winter destinations for many manatees.
In Florida, more than 200 manatees congregate at some power plants during cold weather. These artificially heated sources have allowed manatees to remain north of their historic wintering grounds.
Among the most important of the artificial warm-water discharges are the Florida Power & Light Company's power plants at Cape Canaveral, Fort Lauderdale, Port Everglades, Riviera Beach, and Fort Myers, as well as the Tampa Electric Company's Apollo Beach power plant in Tampa Bay, Florida (Van Meter, 1989).
In dry seasons, West African and Amazonian manatees migrate downstream or into lakes or deeper parts of a river.
One manatee known as "Chessie" traveled 3,220 km (2,000 mi.) from Florida to Point Judith, Rhode Island, and back in 1996. Chessie migrated further north and covered a greater distance than any manatee ever documented.
Population
The Florida manatee census taken in January, 2000, found 2,222 individuals. The 1999 survey was 2,353. Scientists believe there may be as many as 3,000 manatees currently in the state of Florida.
Populations of all species of manatees have apparently declined over the past hundred years. These declines are due to such causes as hunting for their meat, destruction of their habitats, boating, pollution, and low reproduction rates. Antillean, Amazonian, and West African manatee populations are not known due to inadequate scientific research.
