The dugong (Dugong dugon) is a large marine mammal which, together with the three species of manatee, is one of four extant members of the order Sirenia, the only fully-aquatic herbivorous mammals. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's Sea Cow (Hydrodamalis gigas) was hunted to extinction in the 18th century. It is also the only sirenian in its range, which spans the waters of at least 37 countries throughout the Indo-Pacific, though the majority of dugongs live in the northern waters of Australia between Shark Bay and Moreton Bay. In addition, the dugong is the only strictly-marine herbivorous mammal, as all species of manatee utilize fresh water to some degree. Like all modern sirenians, the dugong has a fusiform body with no dorsal fin or hindlimbs, instead possessing paddle-like forelimbs used to maneuver itself. It is easily distinguished from the manatees by its fluked, dolphin-like tail, but also possesses a unique skull and teeth. The dugong is heavily dependent on seagrasses for subsistence and is thus restricted to the coastal habitats where they grow, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as bays, mangrove channels and the lee sides of large inshore islands. Its snout is sharply downturned, an adaptation for grazing and uprooting benthic seagrasses. The dugong has been hunted for thousands of years, often for its meat and oil, although dugong hunting also has great cultural significance throughout its range. The dugong's current distribution is reduced and disjunct, and many populations are close to extinction. The IUCN lists the dugong as a species vulnerable to extinction, while the Convention on International Trade in Endangered Species limits or bans the trade of derived products based on the population involved. Despite being legally protected in many countries throughout their range, the main causes of population decline remain anthropogenic, and include hunting, habitat degradation, and fishing-related fatalities. With its long lifespan and slow rate of reproduction, the dugong is especially vulnerable to these types of exploitation. In addition, dugongs are threatened by storms, parasites, and their natural predators, sharks, killer whales, and crocodiles.
These enormous vegetarians can be found in warm coastal waters from East Africa to Australia, including the Red Sea, Indian Ocean, and Pacific.
Dugongs are related to manatees and are similar in appearance and behavior— though the dugong's tail is fluked like a whale's. Both are related to the elephant, although the giant land animal is not at all similar in appearance or behavior.
Dugongs graze on underwater grasses day and night, rooting for them with their bristled, sensitive snouts and chomping them with their rough lips.
These mammals can stay underwater for six minutes before surfacing. They sometimes breathe by "standing" on their tail with their heads above water.
Dugongs spend much of their time alone or in pairs, though they are sometimes seen gathered in large herds of a hundred animals.
Female dugongs have one calf after a yearlong pregnancy, and the mother helps her young reach the surface and take its first breath. A young dugong remains close to its mother for about 18 months, sometimes catching a ride on her broad back.
These languid animals make an easy target for coastal hunters, and they were long sought for their meat, oil, skin, bones, and teeth. Dugongs are now legally protected throughout their range, but their populations are still in a tenuous state.
Some believe that dugongs were the inspiration for ancient seafaring tales of mermaids and sirens.
Average lifespan in the wild: 70 years
Size: 8 to 10 ft (2.4 to 3 m)
Weight: 510 to 1,100 lbs (231 to 499 kg)
Group name: Herd
References: Husar, S. L. 1978. Dugong dugon. Mammalian Species Account No. 88. American Society of Mammalogists, 7 pp.
Nowak, R. M. 1991. Walker 's Mammals of the World. The Johns Hopkins University Press, Baltimore.
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