Types of Endangered Manatees

An adaptation to diets high in silica, manatee's molar teeth continuously move forward, renewing worn dentition.

Members of the Trichechidae family, manatees inhabit coastal waters and rivers on either side of the Atlantic Ocean. The three species -- the Amazonian, West Indian and West African manatees -- all share similar physical characteristics, including a round, paddle-like tail which serves as a flipper; small eyes in proportion to their body; prehensile lip pads; and whisker-like fibers at the end of their muzzle. Manatees live primarily underwater, but surface to breathe air through valved nostrils. Female manatees have large, pectoral breasts, an attribute which likely lead to their association with mermaids.

Amazonian Manatee

The smallest of the three species, the Amazonian manatee -- Trichechus inunguisn -- inhabits fresh waters of the Amazon River basin and its tributaries in Brazil, Colombia, Ecuador and Peru. Unlike its counterparts, the Amazonian manatee will not enter saltwater, favoring calm, shallow waters, away from human settlements, with abundant aquatic and semi-aquatic plants. During seasonal flooding pulses, this species migrates between the tributaries and lakes, often becoming stranded in these deeper water lakes during the dry season. An exceptionally slow metabolism allows the Amazonian manatee to survive long periods without food. Further differentiating the species from the West Indian and West African manatees, the Amazonian manatee has smoother skin and most have a white or pink belly patch.

West Indian Manatee

The U.S. Fish & Wildlife Service oversees federally designated manatee protection areas in peninsular Florida.

The West Indian Manatee -- Trichechus manatus -- includes two subspecies: the Florida manatee and the Antillean manatee. Florida manatees occur primarily in brackish, fresh and saltwater habitats in Florida and southern Georgia, but in summer months, have been spotted as far north as Massachusetts and west to Texas. Because all manatees have a very slow metabolism, which allows for long periods of fasting, the species can not survive for long in waters below 68 degrees Fahrenheit. Thus they depend on south Florida and Florida's hot springs for their winter range. The Antillean subspecies occupy rivers and coastal waters throughout the Caribbean and Central America, with the greatest stronghold in Belize. Historically, this subspecies was hunted by locals and sold to Europeans for food.

West African Manatee

The least studied of all sirenians, the West African manatee closely resembles the West Indian manatee, though it is somewhat less robust. The species occurs in a wide range of coastal, estuarine and riverine waters, from Mauritania south to Angola, and inland to Mali, Niger and Chad. While the life history of this species has not been well studied, it's believed to largely mirror that of the West Indian manatee in terms of gestation and lifespan. In Africa, peak calving coincides with the start of the rainy season. The West African manatee feeds on a diverse range of plant material -- grasses, emergent plants, fruits and seeds -- as well as occasionally consuming small fish or mollusks.

Threats and Conservation

Hydroelectric dams have genetically isolated populations of both the Amazonian and West African manatees.

Populations of each of the three species of manatees are declining throughout their respective ranges. Low reproductive rates -- one calf only every two to three years -- coupled with human impacts have led to the species being listed as vulnerable under the IUCN Red List of Threatened Species. In the United States, Florida manatees are protected under both the Endangered Species Act and the Marine Mammal Protection Act. Here, collision with motor boats has resulted in significant losses of the species. Threats to West African and Amazonian species are similar, among the most significant: incidental take in fishing nets; hunting and poaching; and loss of habitat to agriculture, particularly rice farming. In 2008, the United Nations Environment Program, Wetlands International, and six West African countries came together to advance cross-national efforts to safeguard the West African manatee across its natural range.

References

• U.S. Geologic Survey: Manatee Sirenia Project
• U.S. Fish & Wildlife Service: Florida Manatee - Issues and Information
• IUCN: Aquatic Mammals in Latin America: Proceedings of a Workshop on Identifying High-Priority Conservation Needs and Actions; R. Hucke-Gaete, et al.; 2004
• Marine Mammal Commission: Florida Manatee
• Afrique Wetlands; Conservation Strategy for the West African Manatee; T. Dodman, et al.; 2008
• IUCN Red List; West African Manatee; J. Powell and A. Kouadio; 2008