Dugongidae: Dugong Family
There is now only 1 species in this family, the other member, Steller’s sea cow, having been exterminated in the 18th century by excessive hunting, only 25 years after its discovery.
The way that dugongs rest, with their heads above the waves, may have been the inspiration for the myth of the mermaid.
The dugong is a very distant relative of the elephant, and is placed in its own order - the Sirenia - along with the manatees. Dugongs live in shallow coastal regions where the sea grass on which they feed is abundant. They rarely make long-distance migrations, though in some places they make daily movements from feeding areas to resting sites in deeper water.
The grazing habits of these marine mammals have led to them also being called sea cows, as they feed on seagrasses growing in the shallows. They never emerge on to land, however. Dugongs live in herds or small family groups. Their similarity to elephants is reflected in the fact that male dugongs have short tusks of ivory, which they may use to settle disputes.
Dugongs have thick, smooth hides, usually dull grey-brown in colour. Unlike the closely related manatees, which have rounded paddle-shaped tails, dugongs have fluked tails like those of whales and dolphins.
Dugongs have unusually shaped mouths, with overhanging upper lips that are specially designed for cropping sea grasses. They can dive for up to three minutes before coming up to breathe, and will swim at up to 20 kph (12 mph) if pursued.
The young are born underwater, after which they ride on their mothers’ backs, breathing when the females come to the surface.
Adults face few dangers, apart from sharks, killer whales and larger crocodilians. Sharks attack dugongs, but groups of dugongs will gang up on them and ram them with their heads. Orcas (killer whales) have also been known to attack dugongs, but by far their greatest enemy is human beings, who have hunted them extensively for their meat, hides and ivory.
Distribution: Occurs throughout coastal areas in the tropical seas, from East Africa and the Red Sea, across the Indian Ocean and the Pacific, south to Australia.
Habitat: Shallow coastal waters.
Weight: 230 - 500 kg (507 - 1100 lb).
Length: 2.4 - 3 m (8 - 10 ft).
Maturity: 8 - 18 years.
Gestation Period: About 13 months; young are cream-coloured at birth.
Breeding: 1; young suckle upside down beneath their mother’s body; weaning takes around 24 months.
Diet: Aquatic vegetation, browsing on underwater grasses; may eat some invertebrates.
Lifespan: Up to 70 years.
The broad flukes provide the propulsive thrust, moving up and down through the water as the dugong swims.
Eyes and ears
The eyes are small, and dugongs have no external ear flaps
Dugongs are grey with a sparse covering of hair over most of the body.
These measure up to 45 cm (17 in) long, and are used for steering.
Dugongs can remain submerged for up to six minutes, and may only put their nostrils above the surface when breathing.
BREACHING THE SURFACE
Sometimes dugongs will be observed "standing", even seeming to embrace each other.
The dugong’s snout turns downwards, and the overhang allows it to dig furrows, uprooting the sea grass.