Dear Matthew, Alexander, Martha and Carmella,

Dugongs are large marine mammals, sometimes called sea cows, that feed on marine vegetation. 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 the seagrasses, which form meadows in sheltered coastal waters. As dugongs feed, whole plants are uprooted so they leave a "feeding trail" behind.

COURTESY www.open-earth.org

Did you know that dugongs are more closely related to elephants than to marine mammals such as whales and dolphins? Their closest living aquatic relatives are the manatees, which reside closer to home than the Great Barrier Reef. Manatees live in the coastal waters of western Florida. Together dugongs and manatees make up the mammalian group Sirenia. They have poor eyesight but relatively good hearing. Dugongs can be up to 3 meters or 10 feet long and weigh 420 kilograms or 930 pounds whereas manatees are slightly bigger (4.5 meters or 15 feet long and 600 kilograms or 1,320 pounds). They can live to be about 60 years old but they reproduce relatively late when they are about 15 or 16 years old.

Dugongs swim using their whale-like fluked tail and they use their front flippers for balance and turning. Their movements are often slow and graceful. They have a rounded head with small eyes and a large snout. The nostrils are at the top of the snout and, like mammals, dugongs must surface to breathe. However, unlike other aquatic mammals such as some whales, dolphins and porpoises, dugongs cannot hold their breath under water for very long. It is generally for only a few minutes, especially if they are swimming fast.

One species of dugongs (Dugong dugon) and three species of manatees (Trichechus) are all endangered. These air-breathing creatures have been hunted in the past to the point of extinction. In fact, the Steller's sea cow, another relative of the dugong, is already extinct, meaning it no longer exists. Dugongs like to spend time at the surface of the water and can be hard to see. Because of this, habitat destruction and boating accidents are the biggest threats to their survival.

Thanks for your question,
Aubie and Dr. Halanych