THE ORDER SIRENIA
Sirenia – Marine Mammals – Sea Cows (4 species)
When looking at a manatee or a dugong up close, it is difficult to imagine why the early sailors often mistook them for mermaids. Perhaps it was the long hours on the sea without female companionship. But “sirens” have been in sailor lore since Odysseus returned from Troy in the “Iliad,” and this mammal order thus received its name.
There are only four species left of the order Sirenia – one dugong and three manatees. The manatee weighs about a ton and a half when fully grown, but the last of the giant 6-ton sea cows, formerly seen in the North Pacific, was slaughtered by man and has been extinct since the 18th century.
Both the manatees and the dugongs are completely aquatic, living in the tropical coastal waters and certain adjacent rivers of the Caribbean Sea and Atlantic South America, as well as Africa and southern Asia to northern Australia. They are large mammals, up to 13 feet long, and somewhat resemble whales or dolphins in shape, as the modifications for marine life have “converged.” The forelimbs are paddles and the hind limbs are absent. The tail is wide and flat and they have no fins.
The skin is thick, wrinkled, and practically hairless except for strong vibrissae (whiskers) around the mouth, the nose is blunt, and they have no external ears. In Sirenians only the cheek teeth are functional. Manatees have a single upper incisor on each side, dugongs have none, and neither has canines. The molars are replaced from behind in the manatees, somewhat as in elephants. The stomach is complex, with three chambers.
Dugongs and manatees are slow, placid, quite defenseless creatures who spend their time browsing marine plant life. Despite their external appearance and aquatic habit, like hyraxes they are most closely akin to elephants, with which they have a common ancestry. As civilization advances, modern motorboats kill the Sirenians with their rotor blades, since these animals tend to eat the water grasses close to shore. Because there is little diversification, due to the fact that there are just so many grasses to eat in the waters, the future of the manatee and dugong is in doubt.
Check out the Dugong and the Manatee.
