Manatees (family Trichechidae, genus Trichechus) are large aquatic mammals sometimes known as sea cows. The Trichechidae differ from the Dugongidae in the shape of the skull and the shape of the tail. Manatees' tails are paddle-shaped, while the Dugong's is forked. It is an herbivore, spending most of its time grazing in shallow waters.
Manatees inhabit shallow, marshy coastal areas of North, Central, and South America, and the Caribbean Sea.
Types
There are four recognized species, more or less similar in appearance but differing geographical distribution.
The African Manatee (Trichechus senegalensis) inhabits the west coast of Africa, while the Amazonian Manatee (T. inunguis) inhabits interior rivers of tropical South America, west to the Peruvian Amazon.
The West Indian Manatee (T. manatus) is found throughout the West Indies and the Caribbean Sea to the southern Gulf of Mexico and the northeast coast of South America to the mouth of the Amazon River. The Florida Manatee is by some considered a distinct species, but ITIS treats it as a subspecies of T. manatus, and this is now accepted. It can reach 4.5 meters (15 feet) or more in length, and lives both in fresh and salt water. It was once hunted for its oil and flesh but is now legally protected.
While T. manatus can be seen in North America even as far northeast as the Hilton Head Island, South Carolina, their largest gathering in North America occurs just inshore from the Gulf of Mexico each winter, near Crystal River Auburndale and Homosassa. There, springs feed comparatively warmer water into the area's rivers.
Vulnerable
All three species of manatee are listed by the IUCN as Vulnerable to extinction. Although it does not have any natural predators, human expansion has reduced its natural habitat in the coastal marsh areas and many manatees are injured by the propellers of outboard motor boats. Manatees will often ingest fishing gear (hooks, metal weights, etc.) during feeding. These foreign materials do not seem to harm manatees, except for monofilament line or string. This can get clogged in the animal's digestive system and slowly kill the animal.
Manatees are killed and injured by propellors and by impacts from boat hulls. They're also crushed in water control structures (navigation locks, flood gates, etc.), drown in pipes and culverts and are occasionally killed due to ingestion of fishing gear (hooks have been known to perforate the GI tract and, as was pointed out, monofilament fishing line can entangle the gut) and entanglement in fishing gear (monofilament line, crab pot float lines, shrimp trawls, cast nets, etc.)
Habitat
Manatees often congregate near power plants, which warm the waters. Some have become reliant on this source of unnatural heat and have ceased migrating to warmer waters. Some power plants have recently been closing and the U.S. Fish and Wildlife Service is trying to find a new way to heat the water for these manatees.
The main water treatment plant in Guyana has three manatees that keep storage canals clear of weeds.
Classification
References
