The dugong, an intriguing marine mammal, navigates the warm coastal waters of the Indo-Pacific. Often referred to as a “sea cow,” this unique creature is the only surviving species within its family, Dugongidae. It is one of four living species in the order Sirenia, which also includes three species of manatees. These gentle, fully aquatic herbivores have a fossil record extending back 50 million years.
Physical Characteristics and Behavior
Dugongs possess a large, torpedo-shaped body that can reach up to 3 meters in length and weigh over 400 kilograms. Their most distinguishing feature is a broad, flattened fluke-like tail, similar to that of a whale or dolphin. Unlike manatees, dugongs lack a paddle-shaped tail and do not have a dorsal fin. Their thick, smooth skin is gray or brownish-gray, sometimes with fine, sparse hairs, particularly around the muzzle.
A downturned snout, featuring a large, horseshoe-shaped upper lip covered with stiff, sensitive bristles, helps them locate and uproot seagrass from the seafloor. Dugongs move slowly and gracefully, swimming at about 10 kilometers per hour. While often solitary, they can also be observed in mother-calf pairs. They surface to breathe, often with only their nostrils visible, and can hold their breath for two and a half to six minutes, though some can remain submerged for up to 12 minutes while feeding.
Habitat and Diet
Dugongs inhabit shallow, protected coastal waters, including bays, mangrove channels, and the waters around large inshore islands. Their geographic range spans the Indo-Pacific region, encompassing over 40 countries from East Africa to the western Pacific Ocean, with Australia hosting the largest contemporary populations. They are the only strictly marine herbivorous mammal, unlike manatees which can utilize freshwater.
Seagrass meadows form almost their entire diet. Dugongs are specialist herbivores, consuming large quantities of seagrass daily, up to 30 to 50 kilograms. They feed by using their muscular upper lip to grasp and uproot whole seagrass plants, including the nutrient-rich rhizomes. This process leaves visible feeding trails on the seafloor.
Reproduction and Lifespan
Dugongs exhibit a slow reproductive rate. Females reach sexual maturity between 6 and 17 years of age and give birth to a single calf after a long gestation period of 13 to 15 months. Births occur in shallow waters, with the mother pushing the newborn to the surface for its first breath. Newborn calves are substantial, measuring around 1.2 meters in length and weighing 30 to 40 kilograms.
The bond between a mother and her calf is strong and extended, with calves nursing for 18 months to two years and remaining close to their mothers for up to seven years. During this prolonged period, the mother teaches the calf how to forage for seagrass. The calving interval can range from 2.5 to 7 years, making population recovery a slow process. Dugongs are long-lived animals, with individuals known to survive for 70 years or more; the oldest documented dugong reached 73 years of age.
Conservation Status and Threats
The dugong is classified as Vulnerable to extinction globally by the International Union for Conservation of Nature (IUCN). This status is concerning given their slow reproductive rate and long generation time, which hinder population recovery from disturbances. The primary threats to dugong populations are largely human-induced and varied across their range.
Habitat loss and degradation pose a threat, mainly through the destruction of seagrass beds. Coastal development, pollution from untreated sewage and agricultural runoff, and destructive fishing practices like trawling and dredging directly damage these underwater meadows. Direct human impacts also include boat strikes, which are often fatal due to increased marine traffic in coastal areas. Entanglement in fishing gear, such as gillnets and shark nets, leads to accidental drownings. Historically, dugongs were hunted for their meat and oil, a practice that has diminished in many areas but still occurs in some regions.