Dugong and Sea Cow: Dugongidae

Physical characteristics: Dugongs are usually gray, with nearly hairless skin. They can grow to be 9.8 feet (3 meters) and weigh around 880 pounds (400 kilograms). Their whale-like tail helps them navigate the waters, as do their flipper-like front limbs. Although both sexes have tusks, they rarely can be seen in females.

Geographic range: Dugongs live in sea grass beds and shallow tropical and subtropical waters of the Indo-Pacific from eastern Africa to the Philippines and the South China and East China Seas.

Habitat: Dugongs live only in shallow coastal saltwater up to about 98 feet (30 meters) deep. The waters must contain sea grass beds.

Diet: Dugongs eat various sea grasses from the ocean floor. Sometimes, in its consumption of sea grass, it will ingest bottom-dwelling invertebrates such as crabs and shrimp. Unlike other sirenians, dugongs cannot hold their breath for long and must surface often for air, which is why the shallow waters are their preferred habitat.

Behavior and reproduction: Despite their large size, dugongs are graceful swimmers. Their tails propel them slowly through the water while the flippers help keep balance. Although their eyesight is poor, dugongs have a well-developed sense of hearing and find sea grass with the help of whiskers that line the upper lip of their large snout.

Dugongs migrate, travel from one region to another on a yearly basis, making regular, short distance (9 to 25 miles [15 to 40 kilometers]) round-trip journeys between feeding areas and warmer coastal areas. In Australia, they have been recorded as making longer trips, ranging from 62 to 373 miles (100 to 600 kilometers).

Dugongs are semi-social, often found in mother-calf pairs, sometimes in a herd with hundreds of individuals. They do not reproduce quickly, just once every three to seven years. After a year of pregnancy, the dugong gives birth to one calf, which will be nursed for anywhere from eighteen to twenty-four months. Dugongs are ready for mating around ten years of age. Males compete for mating rights, and mating often involves numerous males with one female. Male dugongs do not seem to participate at all in the care of the calf.

Dugongs can live for seventy years.

Dugongs and people: Of cultural significance to many native peoples of the Indo-Pacific region, the dugong has been hunted for meat, bones, and hide.

Conservation status: Listed as Vulnerable, the dugong is a protected species in Australia. Dugongs are often victims of boating and fishing accidents. Pollution and dredging, a form of fishing in which nets are scraped along the ocean floor to catch shellfish, are also responsible for the declining dugong population. ∎