Taxonomy/Description

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.

Habitat/Diet

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.

Behavior/Reproduction

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.

Conservation

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.