At maturity they measure from eight to twelve feet and may weigh up to 1500 pounds. Their torpedo-shaped bodies, with very thick skin not unlike an elephant's, are sparsely covered with large hairs, about one hair per square inch. The three manatee species are the African Trichechus senegalensis , the Amazonian Trichechus inunguis , and the West Indian Trichechus manatus , and the one dugong Dugong dugon . The main difference between them is that the manatee's tail is rounded like a spoon, that of the dugong is fluked like a whale's. The largest of the modern Sirenia was Steller's sea cow Hydrodamalis stelleri of the Bering Sea, which was hunted to extinction in the late 18th century.
Manatees appear to be even more critical.
Once to be seen in hundreds and even thousands, manatees are now only found in isolated enclaves along American coasts. In 1976, with all these considerations in mind, I decided to start a manatee research project in Guatemala, which I chose because it is the only place where manatees live in an inland lake, and it seemed that Lake Izabal and the Rio Dulce, which connects it to the Atlantic, might prove both an ideal setting for observations and a good place for a refuge to be developed. Starting in November that year, I aimed to get data on population size, distribution, and general ecology of the Guatemalan manatees which could be used to design conservation and management programmes. I also hoped to get useful information on behaviour and physiology, for besides being rare, manatees are also among the least understood by scientists. Before the Spanish Conquest the manatee was well known by the Mayan Indians of Guatemala.