Dugongs belong to the
Mammalian Order Sirenia. Sirens were mythological beings of the
ocean that lured sailors to their deaths with beautiful singing.
Manatees and dugongs are supposed to have given rise to the mermaid
legend, hence their designation in the order Sirenia. This order
also includes all species of manatees. One may distinguish the
dugong from the manatee species by its tail. A dugong's tail is
shaped like that of a dolphin. A semicircular or crescent shape.
Manatees have a rounder, fully circular tail. Also, unlike
manatees, dugongs do not have toenails on their flippers. The snout
of the dugong is angled much more sharply than that of manatees.
Adult dugongs grow to about 11ft in length and reach weights of
2000lbs. The dugong belongs to the family, Dugongidae. The other
member of this family was Steller's sea cow, which became extinct in
1768. The dugong's scientific name is Dugong dugon, which is
derived from duyong, the Malayan name for this animal.
Despite the dugong's
aquatic appearance, it is not closely related to whales, dolphins,
seals, or sea lions. In fact, its closest relatives are elephants
and hyraxes. Like elephants and hyraxes, dugongs are herbivorous.
Sirenians are the only extant herbivorous marine mammals.
The dugong is the only
ocean dwelling mammalian herbivore. Manatees are primarily
freshwater animals, occasionally venturing into saltwater regions.
The dugong lives throughout the coastal waters of the Indian Ocean.
The range extends north throughout the Philippines and Indonesia,
southeast to the northern coast of Australia, and to the Red Sea and
eastern coast of Africa.
Dugongs forage on a
variety of seagrass species. Seagrasses, which are marine flowering
plants, are distinct from seaweeds, which are algae. The dugongs
feed primarily in shallow waters, digging into the seabed for
seagrass rhizomes. The rhizomes are the carbohydrate rich,
underground storage roots of the seagrass. Some dugong herds
seasonally browse on bush-like seagrasses. Lacking most teeth,
dugongs masticate vegetation with rough pads on their upper and
lower palates. The amount of teeth present in a dugong's mouth are
minimal. A few molars are located in the back of the upper jaw, and
a pair of incisors located in the front of the upper jaw.
Shy, yet curious
creatures, dugong behavior is difficult to study. Dugongs live in
murky waters, and are difficult to observe underwater. Their
curiosity adds another problem to study. When cautiously approached
by divers, dugongs will approach, and a short investigation
follows. Natural behavior stops during these interactions. Such
curiosity would suggest that adult dugongs have few predators. As
shallow water animals, dugongs do not have the ability to submerge
for long periods of time. Nor do they possess advanced adaptations
for speed, endurance, or agility. Dense bones, thick skin, and
rapidly clotting blood are a dugong's main defense.
Male and female
dugongs reach sexual maturity at 9-10 years. After a gestation
period of 13 months, a single calf is born. The calf suckles for
about two years, but remains with its mother for a few years after
weaning. Although dugongs may exceed 50 years of age, a female is
likely to produce no more than five or six offspring throughout her
lifetime. Mother and calf pairs are commonly observed, but most
dugongs live solitary lives, with large herds of several hundred
animals forming on occasion.
Dugongs are protected
in most areas. The United States affords dugongs protection under
the Endangered Species Act. Australia has the largest population of
dugongs, at 85,000, and allows some aboriginal tribes to hunt the
dugong. Papua New Guinea allows some aboriginal tribes this
privilege as well. Modern threats to wild dugongs include, oil
spills, fishing nets, motorboats, and industrial pollution.