Although the dugong looks extremely similar to a manatee, the two are different species. The dugong and the manatee are very closely related and can look almost identical until you look at their tail. The tail of the dugong is typically forked like the tail of a shark, where the tail of the manatee is broad and flat, and slightly more flipper looking than fin looking.
Dugongs are smaller than manatees with the average adult dugong reaching lengths of around 3 meters and weigh nearly 400 kg, which is about the same as a large cow. The front flippers of the dugong can be as much as half a meter in length.
It is thought the legends of mermaids may have originated when sailors from a distance glimpsed dugongs swimming in the water, and mistook them for half-human half-fish creatures. These mermaid legends are also said to be true of the dugongs larger cousin, the manatee.
Dugongs inhabit the warm shallow waters, and despite their large size, dugongs are strictly herbivorous animals and have been referred to as the cows of the sea. Dugongs graze on sea grasses and aquatic plants that grow in abundance in the tropical shallows. Dugongs eat large amounts of sea plants and often leave feeding trails behind of bare sand and uprooted sea grass.
Female dugongs give birth to just one calf about once every five years. The baby dugong is born underwater in the warm shallows, where the baby dugong is immediately able to swim to the surface in order to take its first breath. When the baby dugong is born, the dugong calf is about a meter in length and weighs about 20 kg. The dugong calf will stay close to its mother until the baby dugong is about 2 years old.
Dugong populations are constantly decreasing, with many dugongs being accidental victims in large commercial fishing. Dugongs are now considered to be vulnerable animals but the dugong will commonly get older than 70 years of age. Dugong calves will not reach their full size until they are about 15 years old.