The dugong ( / ˈ d ( j ) uː ɡ ɒ ŋ / ; Dugong dugon ) is a marine mammal. It is one of four living species in the order Sirenia, which also includes three types of manatees. It is the only living member of the family Dugongidae. Its closest relative, Steller's sea cow ( Hydrodamalis gigas ), was hunted to extinction in the 18th century.
The dugong lives in the waters of about 40 countries and territories across the Indo-West Pacific region. It depends on seagrass for food, so it lives in coastal areas where seagrass grows. These areas often include bays, mangrove channels, waters near large islands, and spaces between coral reefs. The northern waters of Australia, between Shark Bay and Moreton Bay, are believed to have the largest dugong populations.
Like all sirenians, the dugong has a streamlined body with no dorsal fin or hind legs. Its front limbs are paddle-shaped. The dugong can be easily recognized by its tail, which resembles a dolphin’s, and by its unique skull and teeth. Its snout points downward, which helps it eat seagrass on the ocean floor. Its molars are simple and peg-like, unlike the more complex teeth of manatees.
People have hunted dugongs for thousands of years for their meat and oil. Traditional hunting is still important in some areas, such as northern Australia and the Pacific Islands. Today, dugongs live in scattered groups, and many populations are at risk of disappearing. The IUCN lists the dugong as vulnerable to extinction. International laws limit or ban trade in dugong products. Even though dugongs are protected in many countries, human activities such as fishing, habitat loss, and hunting remain major threats. Dugongs live up to 70 years or more and reproduce slowly, making them especially at risk of extinction.
Evolution
Dugongs belong to the Sirenia order of mammals that give birth to live young. This group includes modern sea cows, such as manatees and dugongs, as well as their extinct relatives. Sirenians are the only living plant-eating mammals that live entirely in the ocean. Fossils of sirenians date back about 50 million years, from the early Eocene to the present. These animals had a wide variety during the Oligocene and Miocene periods but later decreased in number due to colder temperatures, changes in the ocean, and human activities.
Etymology and taxonomy
The word "dugong" comes from the Visayan (likely Cebuano) word "dugung." The French naturalist Georges-Louis Leclerc, Comte de Buffon, first used the name "dugon" in his book Histoire Naturelle (1765) after descriptions of the animal from Leyte Island in the Philippines. The name originally comes from Proto-Malayo-Polynesian *duyuŋ. It is a common mistake to think the name comes from Malay "duyung," which means "lady of the sea" (mermaid). This is not true.
Other local names for the dugong include "sea cow," "sea pig," and "sea camel." The Wunambal people of the Mitchell Plateau in Western Australia call it "balguja."
Dugong dugon is the only living species in the family Dugongidae. It is one of four living species in the Sirenia order, which also includes manatees. Müller first classified the dugong in 1776 as Trichechus dugon, placing it in the manatee genus defined by Linnaeus. Later, Lacépède named it the type species of Dugong, and Gray and Simpson classified it into its own family and subfamily.
Dugongs and other sirenians are not closely related to most marine mammals. Instead, they are more closely related to elephants. Sirenians, elephants, hyraxes, and aardvarks share a group of animals that all have a common ancestor. Fossils show that sirenians appeared during the Eocene period, likely in the Tethys Ocean. The two living families of sirenians are thought to have separated during the mid-Eocene. Later, in the Miocene, dugongs split from their closest relative, the Steller's sea cow, which went extinct in the 18th century. No fossils of other Dugongidae members have been found.
Scientists have studied dugong populations using mitochondrial DNA. Results suggest that the Southeast Asian population is different from others. In Australia, there are two distinct maternal lineages. One includes dugongs from Africa and Arabia. Limited mixing has occurred between Southeast Asian and Australian dugongs, mostly near Timor. One lineage stretches from Moreton Bay to Western Australia, while the other reaches only to the Northern Territory. More genetic data is needed to clearly define these groups.
Anatomy and morphology
The dugong has a large, round body that gets narrower at both ends. Its skin is thick and smooth, starting as a pale cream color when it is born. Over time, the skin darkens on the back and sides to a brownish or dark grey color. The color of a dugong can change when algae grow on its skin.
An adult dugong is usually no longer than 3 metres (10 feet). A dugong this long weighs about 420 kilograms (930 pounds). Most adults weigh between 250 kilograms (550 pounds) and 900 kilograms (1,980 pounds). The largest recorded dugong was 4.06 metres (13 feet 4 inches) long and weighed 1,016 kilograms (2,240 pounds). It was found near the Saurashtra coast in western India. Female dugongs are often larger than males.
The dugong’s body has very few short hairs, a feature shared by all sirenians. These hairs help the animal sense its surroundings. The hairs are most noticeable around the mouth, which has a large, horseshoe-shaped upper lip. This lip is flexible and helps the dugong find food.
The dugong’s tail and flippers are similar to those of dolphins. The tail moves up and down in long strokes to help the animal swim forward and can twist to turn. The flippers are paddle-shaped and help with turning and slowing down. The flippers lack nails and make up about 15% of the dugong’s body length. The tail has deep notches.
A dugong’s brain weighs up to 300 grams (11 ounces), which is about 0.1% of its body weight. Dugongs have small eyes and limited vision, but they can hear well within specific sound ranges. Their ears are on the sides of their head and do not have visible parts called pinnae. The nostrils are on top of the head and can close using valves. Dugongs have two teats, one behind each flipper. There are few differences between males and females. The main difference is the location of the genital opening, which is near the umbilicus and the anus. The lungs are very long, stretching almost to the kidneys, which are also long to help the dugong survive in saltwater. If a dugong is injured, its blood clots quickly.
The dugong’s skull is unique. It is large, with a sharply downward-pointing part called the premaxilla, which is stronger in males. The spine has between 57 and 60 bones. Unlike manatees, the dugong’s teeth do not continuously grow back. Males develop two incisors (tusks) during puberty. Female tusks grow without emerging during puberty and may appear later in life after reaching the base of the premaxilla. The number of growth layers in a tusk shows the dugong’s age, and the cheek teeth move forward as the animal ages.
The full dental formula of a dugong is 2.0.3.3 3.1.3.3. This means each side of the upper jaw has two incisors, three premolars, and three molars. Each side of the lower jaw has three incisors, one canine, three premolars, and three molars. Like other sirenians, dugongs have pachyostosis, a condition where their ribs and long bones are unusually dense and solid with little or no marrow. These heavy bones, among the densest in the animal kingdom, may help sirenians stay slightly below the water’s surface.
Distribution and habitat
Dugongs live in warm coastal waters from the western Pacific Ocean to the eastern coast of Africa, along about 140,000 kilometers (87,000 miles) of coastline between 26° and 27° north and south of the equator. Their historic range is thought to match the areas where seagrasses from the Potamogetonaceae and Hydrocharitaceae families grow. The full size of their former range is unknown, but today’s populations likely represent the edges of their historical range, which is now broken into smaller areas. During warmer times in the Holocene, their range may have been larger than it is now. Today, dugongs are found in the waters of 37 countries and territories. Scientists believe the number of dugongs recorded is lower than the actual number because surveys are not always accurate. Even with this uncertainty, dugong numbers are thought to be decreasing, with a 20% drop worldwide in the last 90 years. Dugongs have disappeared from the waters of Hong Kong, Mauritius, and Taiwan, as well as parts of Cambodia, Japan, the Philippines, and Vietnam. More disappearances are expected.
Dugongs are usually found in warm coastal waters, with large groups in wide, shallow protected bays. They are the only marine herbivorous mammals, as all manatees live in fresh water to some degree. Dugongs can survive in brackish water near coasts and are often found in shallow mangrove channels and around the leeward sides of large islands where seagrass grows. They typically stay near 10 meters (33 feet) deep, but in areas with shallow continental shelves, they may travel more than 10 kilometers (6 miles) from shore and dive as deep as 37 meters (121 feet) where seagrasses like Halophila spinulosa grow. Different habitats are used for different activities. Shallow waters are often used for giving birth, which helps protect young from predators. Deeper waters may help them stay warm during colder winter months near the shore.
Australia has the largest dugong population, stretching from Shark Bay in Western Australia to Moreton Bay in Queensland. The Shark Bay population is thought to be stable with more than 10,000 dugongs. Smaller groups live farther up the coast, including one near Ashmore Reef. Large numbers of dugongs live north of the Northern Territory, with over 20,000 in the Gulf of Carpentaria. Over 25,000 live in the Torres Strait, such as near Thursday Island, though many move between the strait and New Guinea’s waters.
The Great Barrier Reef is an important feeding area for dugongs, with a stable population of about 10,000. However, the number of dugongs in this area has changed over time. Large northern-facing bays along Queensland’s coast, such as Hervey Bay and Moreton Bay, are important habitats. Dugongs were once seen occasionally along the Gold Coast, but a local population has started to return.
The Persian Gulf has the second-largest dugong population, with numbers between 5,800 and 7,300 along its southern coast. In 1986 and 1999, a group of more than 600 dugongs was seen near Qatar. A 2017 study found a 25% drop in population since 1950. This decline is due to illegal hunting, oil spills, and getting caught in fishing nets.
In the late 1960s, herds of up to 500 dugongs were seen off East Africa and nearby islands. Today, populations in this area are very small, with fewer than 50, and they may soon become extinct. Large groups live on the eastern side of the Red Sea, with similar numbers on the western side. In the 1980s, there were estimated to be 4,000 dugongs in the Red Sea. Dugongs in Madagascar are poorly studied, but overuse has likely caused their numbers to drop sharply. Only about 10 remain near Mayotte. In Mozambique, most local populations are very small, with the largest group (about 120) near Bazaruto Island. Dugongs are now rare in areas like Maputo Bay and Inhaca Island. The Bazaruto Island group may be the last long-term stable population in East Africa, with only part of its habitat protected.
East African dugongs are genetically different from those in the Red Sea and Madagascar. In Tanzania, more dugongs have been seen recently near Mafia Island Marine Park after a failed fishing attempt in 2009. In the Seychelles, dugongs were thought extinct in the 18th century, but a small group was found near Aldabra Atoll. This group may be different from those in other areas. Dugongs once lived in the Chagos Archipelago, which is where Sea Cow Island got its name, but they no longer live there.
Fewer than 250 dugongs live in Indian waters. A small breeding group exists in the Marine National Park in the Gulf of Kutch, the only remaining population in western India. This group is 1,500 kilometers (800 nautical miles) from the Persian Gulf population and 1,700 kilometers (900 nautical miles) from other Indian populations. Former groups in the Maldives and Lakshadweep are likely extinct. A small population remains in the Gulf of Mannar Marine National Park and the Palk Strait between India and Sri Lanka, but it is severely reduced. Recent recovery of seagrass beds in areas like Chilika Lake has raised hopes for dugongs to return. Dugongs near the Andaman and Nicobar Islands are rarely seen, though they were once common during British rule.
A small group of dugongs once lived along China’s southern coast, especially in the Gulf of Tonkin (Beibu Gulf). Efforts to protect them, such as creating a seagrass sanctuary in Guangxi, were made, but numbers continued to fall. By 2007, no dugongs were found on Hainan Island’s west coast. Dugongs were also present in the southern Yellow Sea. The last confirmed sighting in China was in 2008. In 2022, a study in Royal Society Open Science reported that dugongs are functionally extinct in China, based on surveys in Hainan, Guangxi, Guangdong, and Fujian in 2019.
In Vietnam, dugongs are mostly found in Kiên Giang and Bà Rịa–Vũng Tàu provinces, including Phú Quốc Island and Côn Đảo Island, where large groups once lived. Côn Đảo is now the only place in Vietnam where dugongs are regularly seen, protected in Côn Đảo National Park. However, poor attention to marine conservation
Ecology and life history
Dugongs live a long time, and the oldest one found was 73 years old. They have few natural enemies, but young dugongs can be harmed by crocodiles, killer whales, and sharks. A dugong once died from an injury caused by a stingray’s barb. Many infections and parasites affect dugongs, including worms, cryptosporidium, bacteria, and other unknown parasites. About 30% of dugong deaths in Queensland since 1996 are believed to be caused by disease.
Although dugongs are social animals, they are often alone or in pairs because seagrass beds cannot support large groups. Sometimes, hundreds of dugongs gather, but these groups last only briefly. Dugongs are shy and avoid humans, so little is known about their behavior. They can hold their breath for up to six minutes, though two and a half minutes is more common. They sometimes rest on their tails to breathe with their heads above water. Dugongs can dive as deep as 39 meters (128 feet), but they usually stay near the surface, no deeper than 10 meters (33 feet). They communicate using sounds like chirps, whistles, and barks. Visual communication is limited because their eyesight is poor, and it is mainly used for courtship. Mothers and calves are often in close contact, and calves may touch their mothers with their flippers for comfort.
Dugongs are semi-nomadic, traveling long distances to find food but staying within a specific area their whole lives. They often move together in groups, and these movements are likely due to changes in seagrass availability. Dugongs use memory to return to familiar places after traveling. Their movements are influenced by tides, and in areas with large tides, they travel with the tide to reach shallow feeding areas. In Moreton Bay, dugongs move between feeding areas inside the bay and warmer ocean waters. At higher latitudes, they travel to warmer waters during winter. Some dugongs make long trips over many days, even crossing deep ocean areas. One dugong was seen as far south as Sydney. Dugongs can also swim into creeks, with one recorded 15 kilometers (8 nautical miles) up a creek near Cooktown.
Dugongs, like other sirenians, are called "sea cows" because they mainly eat seagrass, especially species like Halophila and Halodule. They swallow the whole plant, including roots, but may eat only the leaves if roots are unavailable. Their stomachs contain many types of seagrass, and they may eat algae when seagrass is scarce. Though mostly herbivores, they occasionally eat invertebrates like jellyfish, sea squirts, and shellfish. In Moreton Bay, dugongs eat invertebrates and algae when their preferred grasses are not available. In some southern areas of Australia, dugongs actively seek invertebrates, but tropical dugongs do not eat them, as shown by their feces.
Most dugongs feed in areas with sparse seagrass rather than lush ones. Factors like protein levels and how quickly seagrass regrows also influence the quality of a seagrass bed. Dugongs prefer seagrass that is low in fiber, high in nitrogen, and easy to digest. In the Great Barrier Reef, they eat Halophila and Halodule to get more nutrients instead of eating large amounts of grass. They prefer younger seagrass growth in areas that are not fully covered by plants. Only certain seagrass meadows are suitable for dugongs because of their specialized diet. Dugongs may alter local seagrass species by feeding, favoring fast-growing, high-nutrient grasses like Halophila and Halodule. Feeding trails have been observed as deep as 33 meters (108 feet), and dugongs have been seen feeding at 37 meters (121 feet). Dugongs swim slowly, about 10 km/h (3 m/s), and walk along the seabed using their pectoral fins.
Dugongs may help certain seagrass species grow by feeding. Grasses like Halophila and Halodule grow quickly in open spaces left by dugong feeding, while slower-growing species like Zosteria capricorni dominate established beds. This behavior is called cultivation grazing and supports the fast-growing, nutrient-rich grasses that dugongs prefer. Dugongs may also eat younger, less fibrous seagrass strands, and feeding in different meadows may provide more young plants.
Dugongs use their sense of smell to find food and have sensitive bristles to feel their surroundings. They dig up plants, shake off sand, and sometimes collect plants in piles before eating them. Their flexible upper lip helps them dig out plants, leaving furrows in the sand.
Dugongs reach sexual maturity between ages 8 and 18, which is older than most mammals. Female dugongs recognize when males are mature by the growth of their tusks, which happens when testosterone levels rise. The age when females first give birth is debated, with some studies suggesting 6 to 17 years. Male dugongs may lose fertility at older ages.
Despite living up to 50 years or more, females give birth only a few times and care for their young extensively. The time between births is unclear, with estimates ranging from 2.4 to 7 years.
Mating behavior varies by location. In some areas, males create territories that females visit, and males compete to attract mates, a behavior called lekking. In other areas, multiple males may try to mate with the same female, sometimes injuring each other or the female. During this, females mate with several males, increasing the chance of conception.
Females give birth after a 13- to 15-month pregnancy, usually to one calf. Births occur in very shallow water, sometimes near the shore. Newborns are about 1.2 meters (4 feet) long and weigh around 30 kilograms (65 pounds). Calves stay close to their mothers, possibly to make swimming easier. They nurse for 14 to 18 months but start eating seagrass soon after birth. Calves leave their mothers only after they mature.
Importance to humans
Dugongs have been easy targets for hunters who kill them for their meat, oil, skin, and bones. Anthropologist A. Asbjørn Jøn has noted that people often think dugongs inspired the idea of mermaids. Cultures around the world developed traditions related to hunting dugongs. In some areas, dugongs remain culturally important, and ecotourism involving dugongs has helped some countries economically.
A 5,000-year-old wall painting of a dugong, likely made by Neolithic people, was found in Tambun Cave, Ipoh, Malaysia. Lieutenant R.L. Rawlings discovered it in 1959 during a routine patrol.
Dugongs appear in Southeast Asian folklore, especially in Austronesian traditions. In languages like Ilocano, Mapun, Yakan, Tausug, and Kadazan Dusun (in the Philippines and Sabah), the word for dugong means "mermaid." In Malay, they are called "perempuan laut" ("woman of the sea") or "putri duyong" ("mermaid princess"), which led to a mistaken belief that "dugong" means "lady of the sea." Some cultures in the Philippines, Malaysia, Indonesia, and Thailand believe dugongs were once human or part-human (usually women) and that they cry when killed or stranded. Killing dugongs is considered unlucky in parts of the Philippines, Sabah, and northern Sulawesi and the Lesser Sunda Islands. In these regions, dugongs were not traditionally hunted for food and remained common until the 1970s.
In other parts of Indonesia, Singapore, Malaysia, Brunei, Thailand, Vietnam, and Cambodia, dugong "tears" are believed to have special effects. Dugong meat is also considered a luxury and thought to have similar effects. In these areas, dugongs are actively hunted, sometimes to near-extinction.
In Palau, dugongs were traditionally hunted with heavy spears from canoes. Although hunting is now illegal and widely disapproved of, poaching remains a serious problem. Dugongs are also hunted in Papua New Guinea, the Solomon Islands, Vanuatu, and New Caledonia, where their meat and bones are valued in feasts and rituals. In some parts of Vanuatu, hunting dugongs is considered taboo. Dugong meat and oil were historically important to Australian Aboriginals and Torres Strait Islanders, who see dugongs as part of their identity.
In southern China, local fishermen once revered dugongs as "miraculous fish" and believed it was bad luck to catch them. Dugongs were common in the region before the 1960s. However, immigrants from other areas who did not share these beliefs began hunting dugongs for food and traditional medicine, leading to a sharp decline in their numbers near the Gulf of Tonkin and Hainan Island. In Japan, dugongs have been hunted in the Ryukyu Islands since ancient times. Carved dugong bones shaped like butterflies are found in Okinawa and were used in rituals. Hunting was common in Japan until the 1970s.
Dugongs also appear in Kenyan legends, where they are called the "Queen of the Sea." Their body parts are used for food, medicine, and decoration. In the Gulf states, dugongs were hunted for food, and their tusks were used as sword handles. In India’s Gulf of Kutch, dugong oil is used to preserve and condition wooden boats, and some people believe the meat has special effects.
Dugongs play a vital role in indigenous marine governance and cultural identity in northern Australia. They are part of "sea-country," a network connecting people, animals, and coastal environments. Modern conservation efforts in the Torres Strait and northern Queensland combine traditional knowledge with scientific methods and shared management practices.
Conservation
Dugong numbers have decreased in recent years. For a population to stay the same, adults cannot die more than 5% each year. Humans can only kill about 1–2% of female dugongs without risking population loss. In places where food is scarce, this number is even lower because fewer baby dugongs are born. Even in the best conditions, a population can grow by no more than 5% yearly, making dugongs vulnerable to overuse. Their habitat in shallow waters puts them at risk from human activities. Research on dugongs and human effects on them is limited, mostly in Australia. In many countries, dugong numbers have never been counted, so population trends are unclear. The only long-term data comes from Queensland, Australia. A major study in 2002 found that dugongs are declining and may be extinct in one-third of their range, with unknown status in another half.
The IUCN Red List says dugongs are vulnerable. The Convention on International Trade in Endangered Species regulates and bans some international trade of dugongs. Most dugong habitats are in proposed marine mammal protection areas. Because dugongs live in many regions, cooperation between countries is needed. In 1998, Southeast Asian countries supported efforts to protect dugongs. Kenya banned hunting and trawling but does not list dugongs as endangered. Mozambique passed laws to protect dugongs in 1955, but enforcement has been weak. France has a plan to protect dugongs in the Mayotte Marine Natural Park.
Marine parks have been created along the Red Sea coast of Africa, and the Gulf of Aqaba in Egypt is fully protected. The UAE and Bahrain banned hunting dugongs in their waters. The UAE also banned drift net fishing and plans to restore dugong habitats. India and Sri Lanka ban hunting and selling dugongs. Japan listed dugongs as endangered and banned killing them. China also banned hunting, catching, and disturbing dugongs. The Philippines was the first country to protect dugongs, but monitoring is hard. Palau passed laws to protect them, but enforcement is weak, and poaching continues. Indonesia listed dugongs as protected in 1999 and started a conservation plan in 2018. Protection is not always enforced, and dugong products are still sold in Bali. Some traditional hunters struggle to find other income after stopping hunting. Dugongs are the national animal of Papua New Guinea, where only traditional hunting is allowed. Vanuatu and New Caledonia also ban hunting. In Australia, dugongs are protected, but rules vary by state, and some indigenous hunting is allowed.
In Queensland, dugongs are listed as vulnerable under the Nature Conservation Act. Many live in marine parks where boats must move slowly and mesh net fishing is limited. The World Wide Fund for Nature bought fishing licenses in northern Queensland to reduce harm. In Vietnam, an illegal network targeting dugongs was shut down in 2012. Concerns about potential hunts along Tanzanian coasts also exist.
Despite legal protections, dugong numbers are falling because of human activities like hunting, habitat loss, and fishing accidents. Many drown in fishing nets, though exact numbers are unknown. Industrial fishing in deep water harms few dugongs, but local fishing in shallow areas is a bigger threat. Dugongs cannot hold their breath long, so they are more likely to die from being trapped. Shark nets caused many deaths in the past but are now banned in most areas. Hunting is less common now, except in some indigenous communities. In northern Australia, hunting has the greatest impact on dugongs.
Vessel strikes harm manatees, but their effect on dugongs is unclear. More boats increase risks, especially in shallow waters. Ecotourism has grown in some countries, but its effects are not well studied. In Hainan, ecotourism has caused environmental harm. Modern farming and land clearing have also damaged habitats. Industrialization is increasing along dugong coasts, with more people living there. Dugongs absorb heavy metals in their bodies more than other marine mammals, but the effects are unknown.
International efforts to protect dugongs face challenges in some developing countries. Shallow waters are used for food and income, and aid to improve fishing can worsen problems. In many places, laws to protect dugongs do not exist or are not enforced.
Oil spills and land reclamation threaten dugongs. In Okinawa, a small dugong population is at risk from U.S. military activity. Plans to build a military base near Henoko reef add threats like noise, pollution, and soil erosion. Local people in Okinawa fought the plans in court, but Japan hid evidence of harm to dugongs during surveys. One dugong has not been seen since 2015, when construction began.
If dugongs do not eat enough, they may delay giving birth or have fewer babies. Food shortages happen because of habitat loss, poor seagrass quality, and human interference. Sewage, chemicals, heavy metals, and other waste harm seagrass. Activities like mining, trawling, and boat propeller damage increase sediment, which smothers seagrass and blocks sunlight. This is the biggest threat to seagrass.
Halophila ovalis, a type of seagrass dugongs eat, dies quickly without light and can disappear in 30 days. Storms and floods can destroy large areas of seagrass and wash dugongs ashore. Seagrass can take over a decade to recover. Protection efforts focus on limiting activities like trawling in seagrass areas, but little is done to stop pollution.