The large, slow-moving dugong (
Dugong dugon) is found in
43 countries along the western Pacific and Indian Oceans (also
known as the Indo-Pacific), with populations ranging from the
coastal waters of East Africa and the Persian Gulf to Japan,
the Philippines, and Australia. With approximately 85,000
animals, Australia has the highest dugong population.
Along with the manatee and the now-extinct Steller's Sea
Cow, the dugong makes up the order Sirenia. The order's name is
derived from the traditional belief that its members inspired
the myths of sirens and mermaids. Somewhat less poetically,
dugong and manatees are also referred to as sea cows.
Adult dugongs, both male and female, can grow to 11 feet or
more in length, and may weigh well over 2,000 pounds. With
their round heads and prominent snouts, dugongs look much like
manatees, but their slate-gray skin is smoother and their shape
is more stream-lined. Like dolphins, dugongs have pointed
flippers, which they may use to "walk" along the sea bed when
feeding, as well as fluke-shaped (split) tails. (This is in
contrast to a manatee's tail, which is shaped like a rounded
paddle.) Male dugongs begin to grow tusks between the ages of
12 and 15 years. If food is plentiful, the habitat protected,
and predation low, dugongs may live more than 70 years.
Dugongs generally inhabit shallow marine areas—bays,
channels, and inshore islands—where their food source,
seagrass, is abundant. Surfacing every minute or two for air,
the dugong forages on bottom vegetation, often leaving long,
bare furrows in seagrass meadows. A thick, movable pad at the
end of the dugong's broad, flat muzzle uproots whole plants and
pushes the food into his mouth.
Dugongs are most often seen alone or in pairs, usually a
mother and her calf, but they have been sighted in large herds
of several hundred. Dugongs have multiple mating partners, and
may breed year-round. Their mating behavior involves groups of
male dugongs splashing, tail-thrashing, and lunging as they
compete for a single female. Calves are born after a 12- to
14-month gestation period, and spend several years with their
mother, even after weaning at 18 months. Both males and females
reach sexual maturity at around 9 or 10 years.
Dugong vocalize underwater with squeaks and squeals,
probably only for short-range communication. Calves have been
observed bleating like lambs when frightened.
Dugongs are natural prey for sharks, killer whales, and
crocodiles, but they are most vulnerable to human activities.
Hunting has drastically reduced dugong populations in some
areas. Although dugong are protected by law in most countries
(under the Endangered Species Act in the United States),
aboriginal subsistence hunting is permitted in Northern
Australia and Papua New Guinea. Currently, dugongs are
threatened by oil spills, entanglement in fishing gear, shark
and turtle nets, dynamite fishing, and the disruption of their
feeding by boats. Dugong habitat is also under pressure from
coastal development, pollution, and other degradation.
