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ManateePhysical characteristics
Like horses, they have a simple stomach, but a large cecum, in which they can digest tough plant matter. In general, their intestines are unusually long for animals of their size. The adults have no incisor or canine teeth, just a set of cheek teeth, which are not clearly differentiated into molars and premolars. Uniquely among mammals, these teeth are continuously replaced throughout life; with new teeth growing at the rear as older teeth fall out from further forward in the mouth. At any given time, a manatee typically has no more than six teeth.
Population
The population of manatees in Florida (T. manatus) is thought to be between 1,000 and 3,000, yet population estimates are very difficult. Manatees are more distantly related to elephants and hyraxes; the latter are small mammals native to Asia and Africa. Manatees are thought to be native to Florida but were brought over by explorers. The number of manatee deaths in Florida caused by humans has been increasing through the years, and now typically accounts for 20%-40% of recorded manatee deaths. In 2006 there were near 300 registered and confirmed manatees in Florida killed by human activity, the majority of these, that happened to be discovered by Florida Fish and Wildlife, have been caused by boat strikes.
Accurate population estimates of the Florida manatee are notoriously difficult and have been called scientifically weak, with widely varying counts from year to year, some areas showing possible increases yet others with decreases, but with very little strong evidence of increases except in 2 areas. However, population viability analysis studies carried out in 1997, found that decreasing adult survival and eventual extinction is a probable future outcome for the Florida manatees, unless they are aggressively protected. Manatee counts are highly variable without an accurate way to estimate numbers, for example, in Florida in 1996, a winter survey found 2,639 manatees, in 1997 a January survey found 2,229, but then a February survey found 1,709. Fossil remains of manatee ancestors show they have inhabited Florida for about 45 million years.
The Amazonian Manatee (T. inunguis) is a species of manatee that lives in the freshwater habitats of the Amazon River and its tributaries. Their color is brownish gray and they have thick, wrinkled skin, often with coarse hair, or "whiskers." Its main predator is also man.
The African Manatee (T. senegalensis) is the least studied of the three species of manatees. Photos of African Manatees are very rare; although very little is known about this species, scientists think they are similar to the West Indian Manatees. They are found in coastal marine and estuarine habitats, and in fresh water river systems along the west coast of Africa from the Senegal River south to the Kwanza River in Angola, including areas in Gambia, Liberia, Guinea-Bissau, Guinea, Sierra Leone, Côte d'Ivoire, Ghana, Mali, Nigeria, Cameroon, Gabon, Republic of the Congo, and Democratic Republic of the Congo. Although crocodiles and sharks occasionally kill manatees in Africa, their only significant threats are from humankind, such as poaching, habitat loss, and other environmental impacts. They live as high upriver on the Niger as Gao, Mali. Although rare, they occasionally get stranded as the river dries up at the end of rainy season and are cooked for a meal. The name in Sonrai, the local language, is "ayyu".
Manatees typically inhabit warm, shallow, coastal estuarine waters and cannot survive below 15° C (288 K; 60° F). Their natural source for warm waters during the winter is warm-spring fed rivers. The West Indian Manatee migrates into Florida rivers such as the Crystal River, the Homosassa River and the Chassawohitzka River. The head springs of these rivers maintain a water temperature of 22° C (299 K; 72° F) year round. During the winter months, November to March, approximately 400 West Indian Manatees (According to the National Wildlife Refuge Service) congregate in the rivers in Citrus County, Florida.
Manatees have been spotted as far north as Cape Cod, and as recently as the late summer of 2006, one made it up to New York City and Rhode Island's Narragansett Bay, as cited by the Boston Globe. According to Memphis, Tennessee's Commercial Appeal newspaper, one manatee was spotted in the Wolf River harbor near the Mississippi River in downtown Memphis, Tennessee, on October 23, 2006, though it was later found dead ten miles downriver in McKellar Lake.
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