Dugong dugon
dugong

Found discontinuously in coastal waters of east Africa from the Red Sea to northernmost South, northeastern Indian, along the Malay peninsula, around the northern coast of Australia to New Guinea and many of the island groups of the South Pacific. Range was greater in the past.

Dugongs inhabit shallow, tropical marine coastal water and are more strictly marine than manatees.

Dugongs are born a pale cream color, but they darken with age to a deep slate gray dorsally and laterally. The short hair is sparsely distributed over the body, save the bristles on the muzzle. The skin is thick, tough and smooth. The front-limbs have evolved into flippers that are 35-45 cm long. These are used for propulsion by young, but the adults use the fluke-like tail for locomotion, using the flippers for steering. Despite its diet, the dugong ha s a relatively simple stomach. The muscular upper lip is cleft and protrudes over the down turned mouth. The lower lip and distal parts of the palate have horny pads used to grasp vegetation, which is then uprooted with the strong upper lip. The dental formula is 0/0 0/0 0/0 2-3/2-3, for a total of 10-14 teeth in adults. The molars are rootless, circular in cross-section and lack enamel. The premaxilla is enlarged and downturned, the nasal bones are absent, the braincase is small and the zygomatic arch is thick and deep. The bones of the skeleton are pachyostotic, which is to say extremely thickened and dense. Adults range in length from 2.4 to 4 m. Sexual dimorphism is either absent or females may slightly outsize males.

Feeding is the principal activity of dugongs and typically occurs in water 1-5 m deep. Wear on the tusks and trails through grass beds suggest that some digging or rooting is part of the feeding behavior. Calluses on the flippers are caused by "walking" on them or drifting across the bottom while feeding. Head shaking during feeding appears to be used to clean sediment from the food before ingesting as little sediment is reported in the stomach contents of animals examined. The timing of feeding seems to be most closely related to tides, not photoperiod. Frightened animals make a whistling sound and calves have a bleat-like cry. Though now rare, herds of several hundred animals were formerly known. Calves formerly left the herd during the day to form nurseries in shallow water. Groups of 6 animals are most common now. Males are not known to stay with the stable mother-calf social units. Long distance migration is unknown, but some daily and seasonal movements do occur in some populations. Tides, water temperature and food abundance are probably the main factors involved in these movements. Average swiming speed is 10 km/hr, but this can be doubled in a pinch. Dives typically last 1-3 minutes.

Dugongs are aquatic herbivores and feed on the phangerogamous sea grasses of the families Potomogetonaceae and Hydrocharitaceae. Also reported to occasionally eat algae, and crabs have been found in the stomachs of dugongs.

Dugongs are hunted throughout their range for meat,which has been likened to veal. They are also hunted for oil, hides for leather, and for their bones and teeth, which are made into ivory artifacts and charcoal for sugar refining. Some Asian cultures prize dugong products for medicinal purposes.

Dugongs are listed as endangered under the Endangered Species Act of the U.S.A. and as vulnerable by the IUCN. All populations are in CITES Appendix I except the Australian populations, which are in Appendix II.

Dugongs have a good fossil record going back to Eocene terrestrial ancestors.