The dugong (Dugong dugon) is the only living species in the mammalian family Dugongidae and one of only four species in its order, Sirenia. It inhabits shallow marine waters from East Africa to Vanuatu, from the Philippines down to Australia. Dugongs grow up to thirteen feet (4 m.) long, and weigh between 500 and 2,000 pounds (225-900 kg). Their smooth skin can be brown or grey, and it is covered approximately every inch with short sensory bristles. They have small eyes and a round oral disk that is densely covered with more stiff sensory bristles. They do vocalize, but unlike whales and dophins (the only other fully aquatic marine mammals), they do not utilize echolocation. Dugongs are similar in overall appearance to other sirenian species (the manatees). Differences include more caudal location of their nostrils on their snout than manatee nostrils and their tails are fluke-like, as opposed to the round tail seen in manatees.
Dugongs are herbivores. Sea grasses are consumed preferentially, but they will also eat some algae. Dugongs have molars that continue to grow throughout life. This may be beneficial to counteract the dentally abrasive effects of the silica that naturally occurs within the plants of their diet. Dugongs are strictly marine and therefore do not require fresh water, though they will drink it if it is provided.
Multiple anthropogenic activities, including hunting, watercraft collisions, fishing gear entanglement, and habitat loss and degradation have had negative impacts on the dugong. Natural occurrences also cause mortalities, including extreme weather phenomena such as cyclones and predation by sharks and orca whales. Dugongs reproduce slowly, and provide a great deal of maternal investment; the calf suckles for at least 18 months. These factors make dugongs slow to rebound from population declines. The IUCN Red List of Threatened Species lists dugongs as Vulnerable to extinction (Marsh 2008).