Mammals
Dugong
Dugong dugon · also called sea cow
The dugong is a large, grey, slow-moving mammal that spends its life grazing meadows of seagrass on the sea floor, which is exactly why sailors called it a sea cow. It is the last living member of its family, its giant cousin having been hunted to extinction in the 1700s, and it is very probably the animal that lies behind centuries of mermaid stories.
Overview
Dugong dugon is a fully marine sirenian, up to about 3 m and 400 kg, found in the warm shallows of the Indian and western Pacific oceans. It eats almost nothing but seagrass, uprooting it with a broad, bristled, downturned upper lip and leaving feeding trails across the meadow. It differs from the manatees in its whale-like forked tail and, in males, a pair of small tusks.
The last sea cow of its kind
The dugong is the only surviving species of the family Dugongidae. Its only recent relative, the enormous Steller’s sea cow, was wiped out by hunters within 27 years of being described, by 1768.
Slow to recover
A female dugong does not breed until she is 10 to 17 years old, then produces one calf every three to seven years, and can live past 70. That slow life means a population knocked down by lost seagrass, net drownings, boat strikes, or hunting recovers extremely slowly, if at all.
Status
The dugong is Vulnerable and declining. Australia holds the great majority of the world’s dugongs, in Shark Bay, the Great Barrier Reef lagoon, and Torres Strait. Elsewhere most populations are small and shrinking, several are near disappearance, and the dugong was declared functionally extinct in Chinese waters in 2022.
Dugong: common questions
What is the difference between a dugong and a manatee?
They are the two living kinds of sirenian, or sea cow, and they look broadly similar, being large, grey, slow, plant-eating marine mammals with paddle-like front flippers and no hind limbs. The main differences are the tail, the snout, and where they live. A dugong has a whale-like tail fluke with two pointed lobes and a strongly downturned snout adapted for grazing seagrass off the sea floor, and it lives only in the warm salt water of the Indian and Pacific oceans. A manatee has a single rounded, paddle-shaped tail and a less downturned face, is more flexible about fresh and salt water, and lives in the Atlantic, in the Caribbean, off West Africa, and up rivers in the Amazon. Male dugongs also grow small tusks, which manatees do not.
Do dugongs really explain mermaid legends?
They are one of the better real-world candidates. A dugong, and its Atlantic relative the manatee, is a large, roughly human-sized mammal that comes to the surface to breathe, can hold a single calf against its body while nursing, sometimes rises vertically in the water with its head and shoulders exposed, and has a broad tail that from a distance and through spray might be taken for something other than a fish tail. Sailors on long voyages, seeing such an animal briefly in poor light, recorded sightings of mermaids and sirens. Christopher Columbus famously noted seeing three mermaids off Hispaniola in 1493 that were, he said, not as beautiful as they are painted, and these were almost certainly manatees. The scientific order name, Sirenia, comes directly from the siren myth.
Why are dugongs threatened?
Their fundamental problem is that they depend entirely on seagrass meadows, which are among the most vulnerable of marine habitats. Coastal development, dredging, land runoff carrying sediment and nutrients, and severe weather such as cyclones and floods can wipe out large areas of seagrass, and a dugong population that loses its feeding grounds either starves, fails to breed, or moves away. On top of that, dugongs drown in gill nets and shark nets and are struck by boats, they are hunted for meat, oil, and tusks in many parts of the range, and in some regions they are taken in Indigenous traditional harvests. Because a female produces so few calves in a lifetime, even a modest steady loss of adults sends a population into decline.
Where is the best place to see a dugong?
Australia, which holds the overwhelming majority of the world's dugongs. The clear, shallow, seagrass-rich waters of Shark Bay in Western Australia, the Great Barrier Reef lagoon and Moreton Bay in Queensland, and the Torres Strait support tens of thousands of animals, and licensed boat tours in a few of these areas offer a realistic chance of seeing one. Elsewhere, small numbers persist around the Red Sea coast of Egypt, parts of the Persian Gulf, the Andaman Islands, and scattered sites in East Africa and Southeast Asia, but populations there are fragile and encounters are rare. Wherever they occur, dugongs are easily disturbed, so viewing should be slow, quiet, and at a distance.