West Indian Manatee or Sea Cow

Trichechus manatus

Description

The West Indian manatee is about 3 meters long (some as large as 4.5 meters) and weigh between 200 and 600kg (the largest weighing 1,500 kg). The female manatee is generally larger than the males. They have grey-brown seal-shaped bodies, sparsely covered in hair; with forelimbs (flippers) and a large paddle like tail. The snout of this species is bent further down than other species of manatee.

Habitat

The West Indian manatee is found through the Caribbean, along the coast of Central America and the northern coast of South America (as far as Brazil). They are restricted to tropical climates because the West Indian manatee does not have a thick layer of fat and therefore does not have the proper insulation, and also because they have a very low metabolic rate. They can commonly be seen in shallow coastal areas, rivers, estuaries, and canals; moving freely between freshwater and marine habitats. They are large in size and prefer water depths of at least 1-2 meters and generally avoiding water depths greater than 6 meters.

Feeding Behavior and Diet

These manatees are opportunistic feeders, eating a variety of leaves from plants, preferring sea grasses from the sea floor. They use their downward bent snout to grasp the plants. They have a flexible split upper lip which they use to bring food into their mouths. Manatees have also been seen using their flippers to dig up plant roots for consumption. The molars of a West Indian manatee are replaced throughout its lifespan as they wear down. Some manatees occasionally eat invertebrates and fish. Manatees graze for 6-8 hours every day, consuming 5-10 percent of their body weight. Their low metabolic rate allows them to survive on 25 percent less energy than other mammals their size. During digestion, manatees break down cellulose of plants consumed by hind-gut fermentation (similar to that of a horse).

Reproduction

West Indian manatees are solitary mammals, but males will follow a female during breeding. One female (cow) may attract up to 20 males while in estrus. The gestation period of a manatee is 12-14 months. Cows give birth to one calf (there have been records of twins) and will not reproduce again for another 3-5 years. A newborn manatee (calf) is about 1.2-1.4 meters long and weighs 30 kg. The calves are darker in coloration than the adults, which fades after about a month. Caves are dependent on their mothers for 2 years, nursing underwater from teats located behind the mother’s forelimbs. Calves are born with molars and premolars that allow them to begin consuming plants after the first 3 weeks. Female manatees (cows) reach sexual maturity after 4-5 years while the males (bulls) reach sexual maturity after 9-10 years.

Months and Times of Activity

This species spends the winter in Florida and then migrates north as far as Virginia and also as far West as Louisiana to spend the summer. They are active day and night, resting near the surface or bottom (surfacing every few minutes to breath) of the water for several hours at a time.

Special Features, Stories, Relationships

• The lungs of this animal extend the length of its body (not including the tail). This helps them to control how close they swim to the surface of the water.
• Their skin continuously sloughs off to reduce the buildup of algae on their skin.
• The West Indian manatee is an endangered and protected species. Populations have been threatened by hunters in Central and South America, and also the activities of humans. Manatees have frequent collisions with motorboats, get caught in fishing nets, and are killed in canal locks every year. Their low reproductive rate makes for difficult population recovery.
• The Florida manatee is a subspecies of the West Indian manatee.
• To read manatee myths go to: http://www.theoceanadventure.com/FMIE/FM10.html
• Children’s book featuring this animal: I’m a Manatee by John Lithgow

References

Edwards, H. 2000. "Trichechus manatus" (On-line), Animal Diversity Web. Accessed November 04, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Trichechus_manatus/