The dugong is the quiet cousin of the manatee: a slow, grey grazer that spends its life nosing through seagrass meadows in warm, shallow water. Sailors once took it for a mermaid, and its name comes from the Malay duyung, often translated as “lady of the sea.” Today it is one of the most specialised mammals in the ocean, tied to a single type of food and a single type of habitat, and that specialisation is both its strength and its weakness. This page is our hub for dugongs, with the key facts and links to everything else we have on the species.

I have dived in several places where dugongs live, including New Caledonia’s lagoon, Vanuatu and the Red Sea. Those are seagrass-and-reef coastlines, and when you understand what a dugong needs, you start to read those shallow sand-and-grass flats differently: not as the dull bit between dive sites, but as pasture.

What kind of animal is a dugong?

A sirenian: a member of the order Sirenia, the “sea cows,” which also includes the three living manatees and the extinct Steller’s sea cow.

Sirenians are the only fully aquatic mammals that eat plants. Their closest living relatives on land are elephants and hyraxes, and like elephants they have thick skin, small eyes and teeth that are replaced or grow in unusual ways. The dugong is the only living member of its family, the Dugongidae. Its giant relative, Steller’s sea cow, lived in the cold Bering Sea, reached about 8–10 m and was hunted to extinction by 1768, within about 27 years of its discovery by Europeans.

Dugongs and manatees are often confused, but they are easy to tell apart once you know the tail. A dugong has a fluked, crescent-shaped tail like a dolphin’s; a manatee has a broad, rounded, paddle-shaped tail. Dugongs are also strictly marine, while manatees move freely into rivers and springs. Our guide to dugong vs manatee goes through all the differences.

How big is a dugong?

Adult dugongs usually measure about 2.5–3 m and weigh roughly 250–450 kg, with occasional larger animals recorded. Unlike many marine mammals, males and females are about the same size. The body is smooth and spindle-shaped, covered in thick skin with sparse short hairs, and coloured pale grey to brown, often paler underneath. There are no hind limbs, and the front limbs are short flippers used mainly for steering and for “walking” along the bottom while feeding.

The head is the most distinctive part. The snout ends in a broad, flattened, downturned muzzle, called the rostral disc, covered in stiff bristles. It is perfect for rooting along the seabed. The mouth points down rather than forward, so a dugong grazes with its face pressed to the bottom, which is why it struggles to feed on anything other than plants growing on the seafloor.

What do dugongs eat?

Seagrass, and almost nothing else. Dugongs often eat the whole plant, roots and rhizomes included, leaving meandering “feeding trails” of bare sand behind them.

Dugongs prefer fine, low-fibre, high-nitrogen seagrasses such as species of Halophila and Halodule, which are easier to digest. An adult eats a large amount each day, and its gut is long, with fermentation in the hindgut breaking down plant material. Where seagrass is scarce, dugongs have been seen eating algae and even small invertebrates, but seagrass remains the foundation of the diet. Their grazing is a form of gardening: by pulling up older plants it can encourage the faster-growing species they prefer. For more, see our page on seagrass meadows.

Where do dugongs live?

Dugongs live in warm, shallow coastal waters from East Africa and the Red Sea, through the Persian Gulf, India and Southeast Asia, to northern Australia, Papua New Guinea, New Caledonia and Vanuatu. In total they occur off the coasts of roughly 40 countries and territories. Australia holds by far the largest numbers, with major populations in Torres Strait, the Great Barrier Reef region, the Northern Territory and Western Australia’s Shark Bay. Elsewhere, populations are often small and scattered, and in some places they have disappeared altogether.

They stay in shallow, sheltered water where seagrass grows: bays, lagoons, mangrove channels and the lee of islands and reefs. Most feeding happens in water a few metres deep, although dugongs have been recorded feeding much deeper on deep-water seagrass beds.

Dugong tusks and teeth

Male dugongs grow a pair of tusks, which are really upper incisors. They usually erupt when a male reaches sexual maturity and are used in courtship and fights between males, sometimes leaving scars on rivals and females. Females’ incisors normally stay hidden under the skin, though tusks occasionally erupt in old females. Behind the tusks, dugongs have a few simple, peg-like cheek teeth; much of the grinding is done by rough, horny pads in the mouth. Like counting tree rings, scientists can estimate a dugong’s age from growth layers in its tusks, which is how lifespans of around 70 years were worked out.

How do dugongs breed?

Slowly. Females typically have their first calf between about 6 and 17 years old, carry it for around 13–15 months, and then wait several years before the next one.

A calf is born underwater, about 1.2 m long, and swims to the surface for its first breath. It stays close to its mother for 18 months or more, suckling from teats in her armpits and learning where to graze. Because each female produces so few young over a long life, even small increases in deaths from boats, nets or hunting can push a population into decline. That reproductive rate is the single most important fact for understanding dugong conservation.

Are dugongs endangered?

Globally the dugong is listed as Vulnerable on the IUCN Red List. In 2019 the IUCN assessed two regional populations separately and listed the East African dugong as Critically Endangered and the New Caledonia population as Endangered. In 2022 a study in Royal Society Open Science concluded that dugongs are probably functionally extinct in Chinese waters, and the small population around Okinawa, Japan, has also dwindled to almost nothing. The main threats are entanglement in fishing nets, hunting, boat strikes, and loss of seagrass from coastal development, dredging, pollution and storms.

It is not all bad news. Australia’s populations are large and, in many areas, managed with protected zones and Indigenous-led co-management of traditional hunting. Where seagrass is protected and nets are controlled, dugongs can persist. Those regional differences are why the species can be secure in one country and nearly gone in the next.

Dugongs and the mermaid legend

Dugongs and manatees are often named as the source of mermaid stories. Seen at a distance, a dugong surfacing with its head and shoulders out of the water, or a mother cradling a calf, could plausibly have fed sailors’ tales. The scientific order name, Sirenia, comes from the sirens of Greek myth. Our page are mermaids real? traces how that idea grew.

Where to see a dugong

If I were planning a trip specifically for dugongs, I would look at Western Australia’s Shark Bay, Moreton Bay near Brisbane, or Marsa Alam on Egypt’s Red Sea coast, where individual dugongs have been known to feed in shallow bays visited by snorkellers. New Caledonia and Vanuatu also have dugongs, though sightings are less predictable. The rules everywhere are the same: never chase, touch or block a dugong, keep a respectful distance, and stay away from mothers and calves. A dugong that is disturbed while feeding has to find another patch of grass, and the energy budget of a grazer is tighter than it looks.

Dugong guides on TheSea.Org

Start with the pages below for more on dugongs and their relatives.