The West Indian Manatee (Trichechus manatus) is a large aquatic mammal that is native to the coastal areas of the Gulf of Mexico, the Caribbean and the northern parts of South America. (The Florida population is sometimes listed as a separate subspecies, Trichechus manatus latirostris.) West Indian Manatees can reach lengths of 10 feet and weigh as much as 1,200 pounds. There are three other members of the group Sirenidae–the West African Manatee (Trichechus senegalensis), the Amazon Manatee (Trichechus inunguis), and the more distantly related Dugong (Dugong dugon) from the Indian Ocean. A fifth species, the much-larger Steller’s Sea Cow (Hydrodamalis gigas) once lived in the Bering Sea but was driven extinct by human hunters in the 1770’s. All of the existing Sirenids are threatened or endangered in the wild.
In appearance, the Manatee is a large rotund animal with two flipper-like paddles in front and a large rounded flat tail in back. The gray wrinkled skin is bare except for a few coarse bristles, and a dense mustache of whiskers on the upper lip. Their back is often encrusted with algae. They are totally aquatic and never leave the water. Although they can enter both fresh and salt water, they require warm temperatures and are limited to tropical areas where the water temperature seldom goes below 70 degrees. They are often found in estuaries, rivers, canals, and freshwater springs connected to the sea.
Despite being large and muscular, they are very placid and slow-moving animals, paddling along slowly in search of the aquatic plants they graze on. They are very good swimmers, though, and often undertake long migrations. During warm summers they can sometimes found in coastal areas as far north as Massachusetts. As mammals, they surface every so often to breathe, often just protruding their nose above the surface. They can hold their breath up to 20 minutes. Manatees eat up to 10% of their body weight a day in sea grasses and other aquatic plants.
The upper lip is elongated and prehensile, serving as a tool for the limbless animal to grasp plants. (The elongated upper lip also gives a clue to the Manatee’s ancestry–the fossil record shows that the Sirenids evolved about 60 million years ago from four-footed wading mammals closely related to the elephants.)
In many tests, Manatees have demonstrated a level of intelligence similar to sea lions or dolphins.
Manatees, like most large mammals, have a very slow rate of reproduction, with just one calf every three or four years. They don’t have a regular breeding season, though most calves are born in the spring. Pregnancy lasts for 12 months. At birth, the newborn Manatee is about 3.5 feet long and weighs about 50 pounds. Young Manatees stay with their mother for about two years before going off on their own, reaching sexual maturity at about five years old.
As Florida’s human population grew in the 60’s and 70’s, the Manatees suffered devastating losses. Commercial and residential development of seashores led to a huge loss in seagrass beds, one of the Manatee’s primary food sources. Another widespread cause of death was collisions with motorboats–the slow-moving Manatees cannot get out of the way of a fast-moving boat. Even today, nearly every surviving Manatee you see will have a network of scars on its back caused by a boat propeller (field researchers use these scars to identify each individual Manatee).
To protect the species, the West Indian Manatee was included in the 1972 Marine Mammal Protection Act and was listed in the 1973 Endangered Species Act. In 1978, Florida passed its own Manatee Sanctuary Act. A massive effort was launched to restore the lost seagrass bed habitats, to establish “no wake” zones and manatee sanctuaries where motor boats are prohibited, and to educate boaters about protecting Manatees. It is estimated today that there are about 5,000 Manatees living in Florida.
The Manatee’s cuddly appearance and gentle disposition have made them very popular with snorkelers and divers. Tourist areas like Crystal River have been built around Manatee habitat, especially warm-water areas like freshwater springs and power-plant lagoons where the Manatees tend to congregate in the winter. Although Federal and State law prohibit approaching the Manatees, the inquisitive animals often will themselves approach the humans on their own, seeming to enjoy the interaction. Florida residents who live near saltwater canals often drape a garden hose into the water during summer, where wandering Manatees will drink from the freshwater (they can’t drink saltwater) and then play with the hose.