Manatees: Trichechidae

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MANATEES: Trichechidae

WEST INDIAN MANATEE (Trichechus manatus): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

The almost-hairless manatee is 9 to 13 feet (3 to 4 meters) long and weighs between 1,100 and 3,300 pounds (500 to 1,500 kilograms), depending on the species. Manatees never stop growing as long as they are alive. The tail is paddle-like, and the flipper-like forelimbs have three to four fingernails except in the Amazonian manatee, which has no fingernails. Manatees are brownish gray. Their eyes are tiny and are placed on the sides of the head. Their flexible lips help them manipulate food so that they can get it into their mouths.

Manatees have a well-developed sense of smell and hear very well. Their eyesight, however, is not very good. Manatees communicate through a series of whistles and chirps.

The manatee is a relative of the elephant. The nose or snout of a manatee acts much like the trunk of an elephant in that it is used to gather food and bring it to the mouth. Their fingernails or toenails, depending on how you look at it, are also similar to those of the elephant.

GEOGRAPHIC RANGE

Manatees live on both sides of the Atlantic Ocean. In the west, they are found from the southeastern United States throughout the Caribbean region to southeastern Brazil and in rivers of the Amazon River Basin. Manatees migrate, travel from one region to another, seasonally, to Florida coastal waters during the winter months. In the east, they live along the African coast, from Senegal to Angola.

HABITAT

Manatees live in shallow coastal waters and estuary (EST-yoo-air-ee) waters, where saltwater and fresh water mix. They also need areas where marine vegetation is plentiful.

DIET

Manatees are primarily vegetarian, though they do sometimes ingest shrimp, snails, or crabs as they feed on ocean-floor plants. A large manatee eats up to 200 pounds (91 kilograms) of sea grass and algae (AL-jee) each day.

BEHAVIOR AND REPRODUCTION

Manatees are semi-social and usually found in mother-calf pairs. They communicate using sound, sight, taste, and touch. Communication is particularly important for developing and maintaining the cow-calf bond.

Manatees are polygamous (puh-LIH-guh-mus), having more than one mate. In fact, a female can be pursued by as many as twenty males during the breeding season, so it is virtually impossible to determine who the father of a calf is. Males do not seem to take part in caring for the young.

Female manatees give birth every two-and-a-half to three years. Usually only one calf is born after a year-long pregnancy. Depending on the species, manatees are ready to breed anywhere between the ages of two to eleven, and they do so throughout the year. Calves are born weighing 60 to 70 pounds (27 to 32 kilograms).

Manatees are unable to hold their breath for long periods of time, so they surface for air about every three minutes except during sleep, at which time they can rest for twenty minutes before surfacing. Manatees have no large predator, animal that hunts them for food, other than humans.

YOU ARE NOT THE ONLY ONE WHO CATCHES A COLD

Water colder than 68°F (20°C) can lead to sicknesses, such as pneumonia, in manatees. The colder waters make it harder for the manatees to get proper nutrients, so they are more likely to get sick. That is why they migrate to warmer waters in Florida during the winter, but even those waters can get too cold.

The waters surrounding Florida's power plants are warmer and 60 percent of manatees now spend time there. Scientists are worried because some of these power plants are getting too old and must be closed, and without the warmer waters more manatees may die as a result of illness.

MANATEES AND PEOPLE

It is not uncommon for a manatee to have scars on its back due to collision with a recreational boat, and these accidents are the primary cause of death for the manatee population. Though law prohibits the deliberate killing of manatees, they are still hunted for food in many areas.

CONSERVATION STATUS

All manatees are considered Endangered, facing a very high risk of extinction in the wild, according to the World Conservation Union (IUCN). The main cause of death is habitat destruction and human activity, specifically recreational boating accidents.

WEST INDIAN MANATEE (Trichechus manatus): SPECIES ACCOUNT

Physical characteristics: Also known as the Florida manatee, the West Indian manatee grows to 13 feet (4 meters) in length, and can weigh up to 3,300 pounds (1,500 kilograms). The nearly hairless skin is gray, and the body has no hind limbs. The tail is wide and paddle-like, and the front limbs each have three to four fingernails. The eyes

are small and located on the sides of the head, and though there are only tiny ear openings, the manatee has a keen sense of hearing. The West Indian manatee uses its flexible lips in conjunction with its flippers to get food into its mouth.

Manatees communicate by whistling, chirping, and squeaking.

Geographic range: Found in the eastern coastal waters of the United States, from upper Virginia to the tip of Florida, around the west coast of Florida to Louisiana. Rare sightings have occurred in waters off New York, Texas, and the Bahamas.

Habitat: The West Indian manatee lives in coastal and estuary waters.

Diet: West Indian manatees eat more than sixty species of vegetation including sea grasses, algae, and water hyacinths. They eat between 10 and 15 percent of their body weight every day.

Behavior and reproduction: The basic social unit of the Florida is the female-calf pair, although these manatees do congregate in herds during mating season as well as the winter months, when they migrate to seek refuge in warmer waters.

These polygamous manatees are ready to breed between the ages of two-and-a half and six years, and females give birth every two-and-a-half to three years. Each one-year pregnancy results in the birth of one calf, though twins make up 1 to 2 percent of all births. Mothers nurse, feed with mother's milk, their young. The West Indian manatee can live for more than fifty years.

The manatee has no major predator. Death is usually caused by human activity.

West Indian manatees and people: The West Indian manatee has been hunted as a source of meat, fat, oil, bone, and hide, though it is now protected under law. Those laws, however, are difficult to enforce. The U.S. Fish and Wildlife Service estimates that 25 percent of all Florida manatee deaths are due to boating accidents.

Conservation status: The West Indian manatee is Endangered according to the IUCN, and is protected throughout its range. It is not known how many are illegally hunted for food each year. The primary reason for the decimation of the population is human activity, including pollution, habitat destruction, and recreational boating and fishing.

According to Boat/US Magazine, 2003 proved one of the most deadly years for the West Indian manatee. A record 380 manatees were killed that year. Ninety-eight of those deaths were the result of red tide. Red tide is a naturally occurring phenomena that happens when a type of phytoplankton, microscopic plants, produces chemical toxins, or poisons. These toxins are then released into the water, killing thousands of fish, dolphins, manatees, and other marine life.

Seventy-three Florida manatees died from boating accidents in 2003, the lowest total since 1997. The most recent surveys indicate that the Florida manatee population is over three thousand, a significant increase from six hundred recorded in 1974. ∎

FOR MORE INFORMATION

Books:

Faulkner, Douglas. Of Manatees and Man. Philadelphia: Xlibris Corp., 2000.

Foott, Jeff, and Barbara Sleeper. In the Company of Manatees: A Tribute. New York: Three Rivers Press, 2000.

Periodicals:

Bryner, Jeanna. "Brrr … Manatees Catch Cold." Science World (January 12, 2004): 4–5.

Kalvin, Jim. "Weighing In On the Manatee Debate." Boat/US Magazine (September 2002). Online at http://articles.findarticles.com/p/articles/mi_m0BQK/is_5_7/ai_91085603 (accessed on July 9, 2004).

"Manatee Deaths Up, Boat Toll Down." Boat/US Magazine (March 2004). Online at http://articles.findarticles.com/p/articles/mi_m0BQK/is_2_9/ai_114604599 (accessed on July 9, 2004).