Dugongs are large, solid mammals with short, paddle-like front flippers and a tail with a straight or concave perimeter that is used as a propeller. Their tail differentiates them from manatees, the tail of which is paddle-shaped. Dugong fins resemble those of dolphins, but unlike dolphins, dugongs lack a dorsal fin. Females have mammary glands under the fins from which their calves suckle. Adult dugongs weigh from 230 to 400 kg and can range from 2.4 to 4 m in length. Their thick skin is brownish-grey, and its color can vary when algae grows on it. Tusks are present in all dugongs, but they are usually only visible through the skin in mature males, whose tusks are prominent, and in old females. Their tusks are projections of the incisor teeth. There are no other external physical differences between sexes, as they are monomorphic. Their ears have no flaps or lobes but are nonetheless very sensitive. Dugongs are suspected to have high auditory accuity to compensate for poor eye sight. Their snout is rather large, rounded over and ends in a cleft. This cleft is a muscular lip that hangs over the down-turned mouth and aids the dugong in its foraging of sea grass. Dugongs have a down-tipped jaw which accommodates the enlarged incisors. Sensory bristles that cover their upper lip assist in locating food. Bristles also cover the dugong’s body. Paired nostrils, used in ventilation when the dugong surfaces every few minutes, are located on top of the head. Valves keep them shut during dives.

The only other species known in the family Dugongidae is Hydrodamalis gigas (Steller’s sea cow), hunted to extinction in 1767, just 36 years after their discovery. They were similar in appearance and color to dugongs but were substantially larger, with a body length of 7 to 10 m and weight between 4,500 and 5,900 kg.

Range mass: 230 to 400 kg.

Range length: 2.4 to 4 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike; ornamentation