Head to head
Dugong vs West Indian Manatee
The dugong and the manatees are the only living sirenians, the group of fully aquatic, plant-eating mammals known as sea cows. They look broadly alike, being large, slow, grey, whiskered animals with flipper forelimbs, no hind limbs, and a gentle disposition, and both are thought to lie behind mermaid legends. But they belong to different families and differ in tail, snout, teeth, and where they can live.
| Dugong | West Indian Manatee | |
|---|---|---|
| Family | Dugongidae (one living species) | Trichechidae (three species) |
| Tail | A fluke with two pointed lobes, like a whale | A single rounded paddle |
| Snout | Strongly downturned for bottom grazing | Less strongly downturned |
| Tusks | Short tusks in adult males | None |
| Water | Salt water only | Fresh and salt water |
| Where it lives | Indian and western Pacific coasts | Atlantic; Florida, Caribbean, and river systems |
| Diet | Almost only seagrass | A wide range of water plants |
| Teeth | Simple, worn down over life | Replaced on a slow conveyor belt |
Dugong vs Manatee: common questions
What is the quickest way to tell a dugong from a manatee?
The tail. A dugong has a tail shaped like a dolphin's or a whale's, a horizontal fluke that comes to two points with a notch in the middle. A manatee has a tail shaped like a single large rounded paddle or a spatula, with no points and no notch. Location is almost as reliable, because the two do not overlap: a sea cow in the Indian Ocean, around East Africa, the Red Sea, South and Southeast Asia, or northern Australia is a dugong, while a sea cow in the Atlantic, whether around Florida, the Caribbean, the Amazon, or West Africa, is a manatee. Adult male dugongs also show small tusks at the front of the upper jaw, which manatees never have.
Are dugongs and manatees closely related?
They are each other's closest living relatives, and together with the extinct Steller's sea cow they make up the order Sirenia. Within that order they sit in separate families that diverged tens of millions of years ago, the dugong in the Dugongidae and the manatees in the Trichechidae. Their nearest relatives outside Sirenia are, surprisingly, the elephants, along with the hyraxes and the aardvark, all descended from an ancient group of African mammals. The sea cows took to the water and never left, evolving a fully aquatic life around a diet of marine and freshwater plants, which no other group of mammals has done.
Why are both dugongs and manatees threatened?
They share a set of vulnerabilities. Both depend on shallow, warm, plant-rich coastal and river habitats that are heavily affected by coastal development, dredging, pollution, and the loss of seagrass and freshwater vegetation. Both are slow-moving surface-breathers in waters full of boats, so collisions with hulls and propellers are a major cause of injury and death, especially for the Florida manatee. Both drown in fishing nets, and both are still hunted for meat in parts of their range. And both breed very slowly, with females producing a single calf only every few years and taking many years to mature, so populations recover slowly from any loss. The dugong has already disappeared from Chinese waters and is close to gone in several other regions.