Image of Dugong mother and calf. Image credit Chris Jones

Dugong mother and calf swimming in the Great Barrier Reef Marine Park

Dugongs, or sea cows as they are sometimes called, are marine animals which can grow to about three metres in length and weigh as much as 400 kilograms. They are the only marine mammals in Australia that live mainly on plants.

The name sea cow refers to the fact that they graze on seagrass, which forms meadows in sheltered coastal waters. As dugongs feed, whole plants are uprooted and a telltale feeding trail is left behind.

Dugong play an important ecological role in coastal marine ecosystems, and the status of dugong populations in an area can be used as an indicator of general ecosystem health.

Dugong are more closely related to elephants than to other marine mammals such as whales and dolphins, but their closest living aquatic relatives are the manatees. Manatees are aquatic mammals that live in freshwater rivers and coastal waters of West Africa, the Caribbean, South America and the southern United States (Florida).

Another close relative was Steller’s sea cow, previously found in the northern Pacific. It was hunted to extinction in the 1700's by sealers for its meat. It grew almost three times as long as the dugong and fed on large algae (kelp).