DugongThe dugong is a large marine mammal found in the warm waters surrounding Indonesia and Australia. Although the dugong can be found widely throughout the Indo-Pacific tropics, the highest population of the dugong is concentrated around northern Australia.
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 vulnerableanimals 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.
The West Indian manatee belongs to the scientific order Sirenia and the Florida manatee is a subspecies of the West Indian manatee. Other sirenians include the Amazonian manatee, dugong, Steller’s sea cow (extinct), and West African manatee. The map below shows the range of each sirenian species and a description of each species is included below.
Outside of Florida, not much is known about the population of West Indian manatees or other sirenians in the world. By far, the largest population of West Indian manatees is found in the United States, primarily in Florida. Elsewhere, they are found in small population pockets throughout their range. All sirenian species in the world are listed as endangered or vulnerable by the IUCN – World Conservation Union.
Members of the extant order Sirenia are found in aquatic habitats throughout the tropics and subtropics. Sirenians are the only completely aquatic mammals that are herbivores. Because of their herbivorous nature, all sirenians are found in relatively shallow waters where sunlight can penetrate and stimulate plant growth.
West Indian Manatee
Trichechus manatus latirostris (Florida manatee)
Trichechus manatus manatus (Antillean manatee)
Florida manatees are found in the southeastern United States, mostly in Florida. Antillean manatees are found in the coastal and inland waterways of eastern Mexico, Central America, the Greater Antilles, and along the northern and eastern coasts of South America. Both Florida manatees and Antillean manatees can be found in salt, fresh or brackish waters and feed on marine, estuarine, and freshwater vegetation.
Amazonian manatees are found in the waters of the Amazon River and its tributaries in South America. The smallest member of the family Trichechidae, the Amazonian manatee has smooth skin and no nails on its flippers and feeds on freshwater vegetation.
West African Manatee
The West African manatee is very similar in size and appearance to the West Indian manatee and lives in similar habitat. West African manatees are found in West African coastal areas, but little is known about this species because they have not been widely studied.
Dugongs are found in the Indo-Pacific region of the world. They have smooth skin and a notched tail fluke. They feed on seagrasses and are hunted for food by humans. Dugongs have tusks, but these tusks characteristically erupt through the gums only in males and normally remain unerupted in female dugongs.
Steller’s Sea Cow
At one time, the Steller’s sea cow was found in the cold waters of the Bering Sea, but it was hunted to extinction within 27 years of its discovery in 1741. The largest sirenian on record, the Steller’s sea cow grew up to nine meters (30 feet) in length and weighed around four metric tons (approximately 4.4 tons or 8,818 pounds).
Please Note: Graphics not to scale. All images © Save the Manatee Club.
Did You Know?
In ancient mythology, “siren” was a term used for monsters or sea nymphs who lured sailors and their ships to treacherous rocks and shipwreck with mesmerizing songs. Throughout history, sailors sometimes thought they were seeing mermaids when they were probably seeing manatees or dugongs. With a little imagination, manatees have an uncanny resemblance to human form that could only increase after long months at sea. In fact, manatees and dugongs may have helped to perpetuate the myth of mermaids.