WEST INDIAN MANATEES

The West Indian Manatee, Trichechus manatus, was first recorded by Europeans when Christopher Columbus observed three manatees near Hispaniola in 1493. He thought they were the mythical mermaids.

Today, West Indian manatees inhabit rivers,estuaries and coastal areas of tropical and subtropical regions of the northwest Atlantic Ocean from southeastern USA to the northeast coast of Brazil, including coastal Belize. Their habitat mainly is defined by tepid temperatures (>68 degrees F), shallow water plants and shallow slow flowing rivers and lagoons. They occupy both fresh and salt water.

Nearly all the information about West Indian manatee biology and life history is derived from intensive study over the past 25 years of the Florida manatee (Trichechus manatus latirostris), a subspecies of the West Indian manatee. Adults measure about 10-12 feet long and weigh 1,000-2,000 pounds. They are non-ruminant herbivores and will eat as much as 150 pounds of aquatic plants daily. They rest frequently while submerged coming up to breathe every 3 to 5 minutes. Manatees develop slowly. Females are sexually mature by about 4 years old. Males may take up to 9 years to mature.They breed throughout the year, and females give birth to a single calf after a gestation of 385-400 days. Females nurse the calves for as long as 14 months to two years, and as a result, only breed every 2.5-3 years. Manatees are long lived, probably living for 50-60 years, though they seem to rarely reach this age due to human related mortality, e.g. collisions with motor boats.

Florida manatees are not found in any cohesive social groupings, except for the mother-offspring pair observed during the calf's dependency period. Males seem to travel more than females. Sometimes manatees are found in unorganized groups at warm-water sources or during mating activities. For example, during a female's receptive period, which may last up to two weeks, she attracts a herd of 5-17 males that escort her closely. In keeping with their simple social lives, manatees do not have elaborate courtship displays. Simple underwater sounds do convey some information on mood and social intention. ( photo courtesy Sirenia Project).

Docility, delicious flesh and low reproductive capacity make manatees today one of the most threatened of aquatic mammals. The West Indian manatee and the two other species of extant manatees (West African manatee (Trichechus senegalensis) and Amazonian manatee Trichechus innungulis) are listed as endangered by the U.S. Fish and Wildlife Service, and as vulnerable to extinction by the World Conservation Union. Major threats are poaching for food, collision with boats, entanglement in fishing nets, and loss of feeding habitats. In the USA up to 30% of the deaths are caused directly by humans.

The three species of manatees, and the closely related dugong, are unique in that they are the only plant-eating marine mammals alive today. These four species are placed in the Mammalian Order Sirenia.