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West Indian Manatee Trichechus manatus




November 27, 2010


The West Indian manatee (Trichechus manatus) is a manatee, and the largest surviving member of the aquatic mammal order Sirenia (which also includes the dugong and the extinct Steller's sea cow).

The West Indian manatee is a species distinct from the Amazonian manatee (T. inunguis), and the African manatee (T. senegalensis). Based on genetic and morphological studies, the West Indian manatee is divided into two subspecies, the Florida manatee (T. m. latirostris) and the Antillean or Caribbean manatee (T. m. manatus). However, recent genetic (mtDNA) research suggests that the West Indian manatee actually falls out into three groups, which are more or less geographically distributed as: (1) Florida and the Greater Antilles; (2) Central and Northern South America; and (3) Northeastern South America.

Like other manatees, the West Indian manatee has adapted fully to an aquatic life style, having no hind limbs. Pelage cover is sparsely distributed across the body, which may play a role in reducing the build-up of algae on their thick skin. The average West Indian manatee is approximately 2.7–3.5 m (8.9–11 ft) long and weighs 200–600 kg (440–1,300 lb), with females generally larger than males. The largest individual on record weighed 1,655 kg (3,650 lb) and measured 4.6 m (15 ft) long. This manatee's color is gray or brown. Its flippers also have either 3 or 4 nails so it can hold its food as it is eating.

As its name implies, the West Indian manatee lives in the West Indies, or Caribbean, generally in shallow coastal areas. However, it is known to withstand large changes in water salinity, and so has also been found in shallow rivers and estuaries. It can live in fresh water, saline water, and even brackish water. It is limited to the tropics and subtropics due to an extremely low metabolic rate and lack of a thick layer of insulating body fat. While this is a regularly occurring species along coastal, southern Florida, during summer this large mammal has even been found as far north as Dennis, Massachusetts and as far west as Texas.

The Florida manatee (Trichechus manatus latirostris), a subspecies of the West Indian manatee, is the largest of all living sirenians. Florida manatees inhabit the most northern limit of sirenian habitat. Over three decades of research by universities, governmental agencies, and NGOs, has contributed to our understanding of Florida manatee ecology and behavior, which is more than we know about any other sirenian species. They are found in fresh water rivers, in estuaries, and in the coastal waters of the Gulf of Mexico and the Atlantic Ocean. Females usually have their first calf when they are about 7 or 8 years old. Normally they only have one calf every three years because manatees nurse their calf for 1 or 2 years, but there are rare occurrences of twins. When a calf is born, they usually weigh between 60 and 70 pounds and are between 4 and 4.5 feet. The family unit consists of mother and calf, which remain together for up to 2 years. Males aggregate in mating herds around a female when she is ready to conceive, but contribute no parental care to the calf. Florida manatees may live to be greater than 60 years old in the wild, and one captive manatee -- "Snooty" Snooty -- has lived for 63 years. In captivity, West Indian Manatees live up to 28 years. The biggest single threat to Florida manatees is death from collisions with recreational watercraft. Large concentrations of Florida manatees are located in the Crystal River area and also Wakulla Springs regions in central and north Florida. The best time to see the Wakulla Springs manatees are in November and December, and in the spring for the Crystal River manatees.

The other subspecies of the West Indian manatee is sometimes referred to as the Antillean manatee (Trichechus manatus manatus). Antillean manatees are sparsely distributed throughout the Caribbean and the Northwestern Atlantic Ocean, from Mexico, east to the Greater Antilles, and south to Brazil. They are found in French Guiana, Suriname, Guyana, Trinidad (however there has been a lack of recent sightings), Venezuela, Colombia, Panama, Costa Rica, Nicaragua, Honduras, Guatemala, Belize, Mexico, Trinidad, Cuba, Haiti, Dominican Republic, Jamaica, and Puerto Rico. Historically, Antillean manatees were hunted by local natives and sold to European explorers for food. Today, they are threatened by loss of habitat, poaching, entanglement with fishing gear, and increased boating activity. Several of Sirenian International's scientists study Antillean manatees in Belize, which may be the last stronghold for the subspecies. Funds for research, education, and conservation projects are desperately needed in other Central American nations.