The dugong, Dugong dugon, is a marine mammal often referred to as a “sea cow.” It is the sole living representative of the family Dugongidae, belonging to the order Sirenia, which also includes manatees. They are calm grazers of underwater meadows.
Distinctive Features
The dugong possesses a cylindrical, tapering body that sets it apart in marine environments. Its most distinguishing feature is a fluked tail, similar in shape to those of dolphins or whales, which propels it through the water. In contrast, manatees have a paddle-shaped tail. Dugongs also have paddle-like forelimbs, which they use for steering and manipulating food.
A broad, bristled snout, sharply downturned, is another characteristic adaptation for bottom-feeding on seagrass. Thick sensory bristles, known as vibrissae, on its snout aid in detecting and distinguishing food. Adult dugongs typically range from 2.2 to 3.4 meters (7 to 11 feet) in length and weigh between 230 to 420 kilograms (500 to 925 pounds). While manatees can be larger, dugongs generally have a more streamlined body shape.
Global Range and Habitat
Dugongs are found across a vast expanse of the Indo-Pacific region, inhabiting the warm coastal waters of approximately 40 countries and territories. Their distribution extends from East Africa to Vanuatu, encompassing areas like the Red Sea, the Persian Gulf, and the northern waters of Australia, which are considered a stronghold for the species. A small, isolated population also exists near Palau.
These marine mammals prefer shallow, sheltered coastal waters, including bays, mangrove channels, and the waters around large inshore islands. Their presence is closely tied to the availability of seagrass beds. Seagrass meadows provide sustenance and a protected environment, making these habitats important for their survival.
Feeding Habits
Dugongs are strict herbivores, consuming almost exclusively seagrass. They are specialized grazers, using their muscular, downturned snout to root through the seabed and excavate entire seagrass plants. This feeding behavior often leaves distinctive trails along the seafloor.
While they consume various seagrass species, dugongs often show a preference for pioneer species from the Halophila and Halodule genera, which are highly digestible and rich in nutrients. They are known to consume large quantities, with an adult dugong potentially eating up to 40 kilograms of seagrass per day. Their slow metabolism contributes to their continuous grazing.
Conservation Challenges
The dugong is classified as Vulnerable on the IUCN Red List of Threatened Species, indicating a high risk of extinction in the wild. Population declines are attributed to a range of human-induced threats. Habitat loss and degradation are a major threat, particularly the destruction of seagrass beds due to coastal development, pollution from sewage and chemicals, and the impacts of climate change, such as more frequent and severe weather events.
Accidental entanglement in fishing nets, especially gillnets, is a leading cause of dugong fatalities, as they can drown if trapped. Boat strikes, resulting from increased marine traffic and tourism, also contribute to injuries and deaths. Historically, dugongs were hunted for their meat and oil, and illegal hunting persists in some areas despite legal protections. Conservation efforts include establishing protected marine areas, focusing on safeguarding seagrass meadows, and implementing anti-poaching measures. Community involvement is also being emphasized to support dugong conservation.