It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow (Hydrodamalis gigas), was hunted to extinction in the 18th century.

Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include fishing-related fatalities, habitat degradation, and hunting.

They attained modest diversity during the Oligocene and Miocene but subsequently declined as a result of climatic cooling, oceanographic changes, and human interference.

[6][7][8] The name was first adopted and popularized by the French naturalist Georges-Louis Leclerc, Comte de Buffon, as "dugon" in Histoire Naturelle (1765), after descriptions of the animal from the island of Leyte in the Philippines.

The two extant families of sirenians are thought to have diverged in the mid-Eocene, after which the dugongs and their closest relative, the Steller's sea cow, split off from a common ancestor in the Miocene.

[29] The largest individual recorded was 4.06 metres (13 ft 4 in) long and weighed 1,016 kilograms (2,240 lb),[19] and was found off the Saurashtra coast of west India.

[19] Dugongs are found in warm coastal waters from the western Pacific Ocean to the eastern coast of Africa,[22] along an estimated 140,000 kilometres (87,000 mi) of coastline[31] between 26° and 27° to the north and south of the equator.

[18] Dugongs are generally found in warm waters around the coast[22] with large numbers concentrated in wide and shallow protected bays.

A population exists in the Gulf of Mannar Marine National Park and the Palk Strait between India and Sri Lanka, but it is seriously depleted.

Recoveries of seagrass beds along former ranges of dugongs, such as the Chilika Lake have been confirmed in recent years, raising hopes for re-colorizations of the species.

In August 2022, an article published on the Royal Society Open Science concluded that dugongs were functionally extinct in China, which was based on a large-scale interview survey conducted across four southern Chinese maritime provinces (Hainan, Guangxi, Guangdong, and Fujian) in the summer of 2019.

[69][70][71] Recently, the local marine trash problem in the archipelago remained unabated and became the biggest threat to the already dwindling population of Dugongs in the country.

[13] They have few natural predators, although animals such as crocodiles, killer whales, and sharks pose a threat to the young,[18] and a dugong has also been recorded to have died from trauma after being impaled by a stingray barb.

[18] Dugongs in Moreton Bay, Australia, are omnivorous, feeding on invertebrates such as polychaetes[94] or marine algae when the supply of their choice grasses decreases.

[18] The chemical structure and composition of the seagrass are important, and the grass species most often eaten are low in fiber, high in nitrogen, and easily digestible.

[13] In the Great Barrier Reef, dugongs feed on low-fiber high-nitrogen seagrass such as Halophila and Halodule,[18] to maximize nutrient intake instead of bulk eating.

[101][10][102] A common belief found in the Philippines, Malaysia, Indonesia, and Thailand, is that dugongs were originally human or part-human (usually women), and that they cry when they are butchered or beached.

Because of this, it is considered bad luck if a dugong is killed or accidentally dies in nets or fish corrals in the Philippines, some parts of Sabah (Malaysia), and northern Sulawesi and the Lesser Sunda Islands (Indonesia).

Dugongs are also widely hunted in Papua New Guinea, the Solomon Islands, Vanuatu, and New Caledonia; where their meat and ornaments made from bones and tusks are highly prized in feasts and traditional rituals.

Beginning in the 1950s, a wave of immigrants from other regions that do not hold these beliefs resulted in dugongs being hunted for food and traditional Chinese medicine.

Dugong oil is important as a preservative and conditioner for wooden boats to people around the Gulf of Kutch in India, who also believe the meat to be an aphrodisiac.

[46] Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include hunting, habitat degradation, and fishing-related fatalities.

[13] The military base plans have been fought in US courts by some Okinawans, whose concerns include the impact on the local environment and dugong habitats.

[77][110] It was later revealed that the government of Japan was hiding evidence of the negative effects of ship lanes and human activities on dugongs observed during surveys carried out off Henoko reef.

Sewage, detergents, heavy metals, hypersaline water, herbicides, and other waste products all negatively affect seagrass meadows.

Human activity such as mining, trawling, dredging, land reclamation, and boat propeller scarring also cause an increase in sedimentation which smothers seagrass and prevents light from reaching it.

Extreme weather such as cyclones and floods can destroy hundreds of square kilometres of seagrass meadows, as well as wash dugongs ashore.

Most measures for protection involve restricting activities such as trawling in areas containing seagrass meadows, with little to no action on pollutants originating from land.

[115] The Australian state of Queensland has sixteen dugong protection parks, and some preservation zones have been established where even Aboriginal Peoples are not allowed to hunt.

[120] Gracie, a captive dugong at Underwater World, Singapore, was reported to have died in 2014 at the age of 19, from complications arising from an acute digestive disorder.