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 living 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 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 today.
Like all sirenians, the dugong has a streamlined body with no back fin or legs. Its front limbs are paddle-shaped. The dugong can be easily recognized by its tail, which looks like a dolphin’s, and by its unique skull and teeth. Its snout is angled downward, which helps it feed on seagrass on the ocean floor. Its teeth are simple and peg-shaped, unlike the more complex teeth of manatees.
People have hunted the dugong for thousands of years for its meat and oil. Traditional hunting is still important in some areas, such as northern Australia and the Pacific Islands. Today, the dugong’s habitat is broken into smaller groups, and many populations are near extinction. The IUCN classifies the dugong as a vulnerable species. The Convention on International Trade in Endangered Species limits or stops the trade of dugong products. Although the dugong is protected in many countries, human activities such as fishing, habitat loss, and hunting remain major threats. Because the dugong lives for 70 years or more and reproduces slowly, it is especially at risk of disappearing.
Evolution
Dugongs are part of the Sirenia order, which includes modern "sea cows" like manatees and dugongs, as well as their extinct relatives. Sirenians are the only living group of plant-eating marine mammals that have fully adapted to life in the ocean. Scientists believe the Sirenia order has a fossil record that dates back about 50 million years, from the early Eocene period to the present. These animals had a wide variety of species during the Oligocene and Miocene periods, but their numbers later decreased because of colder climates, 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 the Proto-Malayo-Polynesian word 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 includes manatees. The species was first named Trichechus dugon by Müller in 1776, placing it in the manatee genus defined by Linnaeus. Later, Lacépède classified it as the type species of Dugong, and Gray and Simpson placed it in its own family and subfamily.
Dugongs and other sirenians are not closely related to other marine mammals. Instead, they are more closely related to elephants. Sirenians and elephants share a group that also includes hyraxes and the aardvark, which are among the earliest mammals to branch off from eutherians. Fossils show that sirenians first appeared during the Eocene period, likely in the Tethys Ocean. The two living families of sirenians are believed to have split during the mid-Eocene. Later, dugongs and their closest relative, the Steller's sea cow, separated from a common ancestor during the Miocene. The Steller's sea cow went extinct in the 18th century. No fossils of other Dugongidae members have been found.
Scientists have studied dugong populations using mitochondrial DNA. These studies suggest that the Southeast Asian population is different from others. In Australia, there are two distinct maternal lineages, one of which includes dugongs from Africa and Arabia. Limited genetic mixing has occurred between Southeast Asian and Australian dugongs, mostly near Timor. One lineage stretches from Moreton Bay to Western Australia, while the other extends from Moreton Bay to the Northern Territory. Currently, there is not enough genetic data to clearly define the boundaries between these groups.
Anatomy and morphology
The dugong has a large, round body that becomes narrower at both ends. Its skin is thick and smooth, starting as pale cream 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 may change because algae can grow on its skin.
An adult dugong is usually no longer than 3 meters (10 feet). A dugong this long weighs about 420 kilograms (930 pounds). Adult dugongs typically weigh between 250 kilograms (550 pounds) and 900 kilograms (1,980 pounds). The largest recorded dugong was 4.06 meters (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 usually larger than males.
The dugong’s body has very short hair, a feature shared by all sirenians. This hair may help them sense their surroundings. The hair is most visible around the mouth, where a large, horseshoe-shaped upper lip forms a flexible muzzle. This lip helps the dugong find food.
The dugong’s tail and flippers are similar to those of dolphins. The tail flukes move up and down in long strokes to help the dugong swim forward and can be twisted to turn. The flippers are paddle-shaped and help with turning and slowing down. The flippers do not have nails and are 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, which do not have visible outer parts, are on the sides of their head. The nostrils are on top of the head and can be closed with 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 anus. The lungs of a dugong are very long, stretching almost to the kidneys, which are also long to help the dugong live in saltwater. If a dugong is injured, its blood clots quickly.
The dugong’s skull is unique. The skull is large, and the premaxilla, a part of the upper jaw, points downward. This part is stronger in males. The spine has between 57 and 60 vertebrae. Unlike manatees, the dugong’s teeth do not grow back through horizontal replacement. Males develop two incisors (tusks) during puberty. Female tusks grow continuously but may not emerge until later in life, sometimes reaching the base of the premaxilla. The number of growth layers in a tusk shows the dugong’s age. The cheek teeth move forward as the dugong 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 the ribs and long bones are very dense and contain little or no marrow. These heavy bones 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 historical range likely matched the areas where seagrasses from the Potamogetonaceae and Hydrocharitaceae families grew. The full size of their former range is unknown, but current populations may represent the limits of their historical range, which is now broken into smaller areas. During warmer times in the Holocene, their range might have been larger than it is today. Dugongs are found in the waters of 37 countries and territories. Recorded numbers are likely lower than actual numbers because surveys are not always accurate. Despite this, their population is believed to be decreasing, with a global decline of 20% over the last 90 years. They have disappeared from the waters of Hong Kong, Mauritius, Taiwan, parts of Cambodia, Japan, the Philippines, and Vietnam. More disappearances are expected.
Dugongs are usually found in warm coastal waters, with large numbers in wide, shallow protected bays. They are the only strictly marine herbivorous mammals, as all manatees use fresh water to some extent. They can tolerate brackish water in coastal wetlands and are also found in wide, shallow mangrove channels and on the leeward sides of large inshore islands where seagrass beds are common. They are typically found at depths of about 10 meters (33 feet), though in areas with shallow continental shelves, they may travel more than 10 kilometers (6 miles) from shore, diving as deep as 37 meters (121 feet) where deepwater seagrasses like Halophila spinulosa grow. Specific habitats are used for different activities. Shallow waters are often used for calving, reducing the risk of predation. Deep waters may help them stay warm during winter.
Australia has the largest dugong population, stretching from Shark Bay in Western Australia to Moreton Bay in Queensland. The Shark Bay population is stable, with over 10,000 dugongs. Smaller populations exist further up the coast, including one in Ashmore Reef. Large numbers live north of the Northern Territory, with over 20,000 in the Gulf of Carpentaria alone. Over 25,000 live in the Torres Strait, such as near Thursday Island, though many migrate between the strait and New Guinea waters.
The Great Barrier Reef provides important feeding areas for dugongs, with a stable population of about 10,000. Population concentrations have changed over time. Large bays facing north on the Queensland coast, such as Hervey Bay and Moreton Bay, are significant habitats. Dugongs have recently started to return to the Gold Coast after a period of absence.
The Persian Gulf has the second-largest dugong population, inhabiting most of its southern coast. The current population is estimated to range from 5,800 to 7,300. A 1986–1999 study reported a group of over 600 dugongs near Qatar. A 2017 study found a 25% population drop since 1950. Reasons for this decline include illegal hunting, oil spills, and entanglement in nets.
In the late 1960s, herds of up to 500 dugongs were seen off the coast of East Africa and nearby islands. Current populations there are extremely small, with fewer than 50 individuals, and extinction is likely. Large populations live on both sides of the Red Sea, with estimates of up to 4,000 in the 1980s. Dugongs in Madagascar are poorly studied, but widespread hunting has likely caused severe declines. Only about 10 remain near Mayotte. In Mozambique, most local populations are very small, with the largest (about 120 individuals) on Bazaruto Island. They are rare in historical habitats like Maputo Bay and Inhaca Island. The Bazaruto Island population may be the last long-term viable group in East Africa, though only part of its area is protected.
The East African population is genetically different from those in the Red Sea and Madagascar. In Tanzania, recent observations have increased near Mafia Island Marine Park after a failed hunting attempt in 2009. In the Seychelles, dugongs were thought extinct in the 18th century until a small group was found near Aldabra Atoll. This group may be distinct from others. Dugongs once lived in the Chagos Archipelago, where Sea Cow Island was named after them, but they no longer live there.
Fewer than 250 dugongs live in Indian waters. A small breeding population exists in the Marine National Park, Gulf of Kutch, the only remaining group in western India. It is 1,500 kilometers (800 nautical miles) from the Persian Gulf population and 1,700 kilometers (900 nautical miles) from other Indian populations. Former populations in the Maldives and Lakshadweep are presumed extinct. A small group lives in the Gulf of Mannar Marine National Park and 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 future colonization. The population around the Andaman and Nicobar Islands is rarely seen, though it was large during British rule and is now small and scattered.
A small population once lived along China’s southern coast, especially in the Gulf of Tonkin (Beibu Gulf), where conservation efforts included creating a seagrass sanctuary. Despite this, numbers continued to decline, and by 2007, no dugongs were found on Hainan’s west coast. Dugongs were also present in the southern Yellow Sea. The last confirmed sighting in China was in 2008. A 2022 study concluded that dugongs are functionally extinct in China, based on surveys in Hainan, Guangxi, Guangdong, and Fujian in 2019.
Ecology and life history
Dugongs can live for many years, with the oldest recorded dugong reaching 73 years old. They have few natural enemies, but young dugongs may be harmed by animals like crocodiles, killer whales, and sharks. A dugong has also been recorded to have died after being pierced by a stingray’s barb. Many infections and parasites affect dugongs. Scientists have found several types of parasites and infections, including helminths, cryptosporidium, bacterial infections, 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 are short-lived. Dugongs are shy and avoid humans, so not much is known about their behavior. They can hold their breath for up to six minutes, though they usually breathe about two and a half minutes at a time. They rest on their tails to breathe with their heads above water. Dugongs can dive as deep as 39 meters (128 feet), but they mostly stay within 10 meters (33 feet) of the surface. They communicate using sounds like chirps, whistles, and barks, which echo underwater. These sounds vary in loudness and pitch, suggesting different purposes. Because dugongs have poor eyesight, they rely more on touch for communication, especially during courtship. Mothers and calves are often in close contact, and calves sometimes use their flippers to touch their mothers for comfort.
Dugongs are partially nomadic, often traveling long distances to find food but staying within a certain area their entire lives. Many move together in groups, and these movements are likely caused by changes in seagrass availability. Dugongs use their memory to return to specific places after long trips. Their movements mostly occur within seagrass beds, and each dugong may have a unique pattern of movement. Tides influence daily travel, and in areas with large tides, dugongs move with the tide to reach shallow feeding areas. In Moreton Bay, dugongs travel between feeding areas inside the bay and warmer ocean waters. At higher latitudes, dugongs move to warmer waters during winter. Some dugongs travel long distances over many days, even crossing deep ocean waters. One dugong was seen as far south as Sydney. Dugongs can also swim into creeks, and one was found 15 kilometers (8 nautical miles) up a creek near Cooktown.
Dugongs, like other sirenians, are called "sea cows" because they mainly eat seagrass, especially from the genera Halophila and Halodule. They swallow the whole plant, including the roots, but may eat only the leaves if roots are unavailable. Scientists have found many types of seagrass in dugong stomachs, and some eat algae when seagrass is scarce. Though mostly herbivores, they occasionally eat invertebrates like jellyfish, sea squirts, and shellfish. In Moreton Bay, Australia, dugongs eat invertebrates and algae when their preferred grasses are not available. In other parts of Australia, some dugongs actively seek out large invertebrates, but this is not common in tropical areas, where evidence shows they do not eat invertebrates.
Most dugongs feed in areas with less dense seagrass rather than in lush areas. Factors like the protein content and regrowth ability of seagrass also influence its value. The chemical structure of seagrass is important, and dugongs prefer grasses that are low in fiber, high in nitrogen, and easy to digest. In the Great Barrier Reef, dugongs eat seagrass like Halophila and Halodule, which are high in nitrogen, to maximize nutrients rather than eat large amounts. They prefer younger seagrass in areas that are not fully vegetated. Only certain seagrass meadows are suitable for dugongs because of their specialized diet. Evidence suggests that dugongs may change the types of seagrass in their local areas. Dugongs sometimes feed in deeper water, with feeding trails observed as deep as 33 meters (108 feet), and they have been seen feeding at 37 meters (121 feet). Dugongs swim slowly, at about 10 kilometers per hour (3 meters per second). When feeding on the seabed, they walk using their pectoral fins.
Dugong feeding may encourage the growth of low-fiber, high
Importance to humans
Dugongs have been easy targets for hunters throughout history. Hunters killed them for their meat, oil, skin, and bones. As noted by anthropologist A. Asbjørn Jøn, dugongs are often seen as the inspiration for mermaids. People around the world created cultures and traditions around hunting dugongs. In some areas, dugongs remain important, and ecotourism related to them has helped some countries economically.
A 5,000-year-old wall painting of a dugong, drawn by Neolithic people, was found in Tambun Cave, Ipoh, Malaysia. Lieutenant R.L. Rawlings discovered it during a routine patrol in 1959.
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"). This has led to the mistaken belief that "dugong" means "lady of the sea." In some parts of the Philippines, Malaysia, Indonesia, and Thailand, people believe dugongs were once human or part-human (usually women). It is considered bad luck to kill or accidentally harm a dugong in these areas. Dugongs were not traditionally hunted for food in these regions and were common until the 1970s.
In other parts of Indonesia, Singapore, Malaysia, Brunei, Thailand, Vietnam, and Cambodia, dugong "tears" are believed to have aphrodisiac properties. Dugong meat is also considered a luxury food and is thought to have aphrodisiac effects. In these regions, dugongs are actively hunted, sometimes to the point of near-extinction.
In Palau, dugongs were traditionally hunted with heavy spears from canoes. Although hunting them 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. Their meat and items made from bones and tusks are valued in feasts and rituals. However, in some parts of Vanuatu, hunting dugongs is considered taboo. Dugong meat and oil have been important foods for Australian Aboriginals and Torres Strait Islanders. Some Aboriginal communities view dugongs as part of their identity.
In southern China, local fishermen once revered dugongs as "miraculous fish." They believed it was unlucky to catch them, and dugongs were common before the 1960s. Starting in the 1950s, immigrants from other regions who did not share these beliefs led to dugongs being hunted for food and traditional medicine. This caused a sharp drop in dugong numbers in the Gulf of Tonkin and around Hainan Island. In Japan, dugongs were hunted in the Ryukyu Islands since ancient times. Carved dugong ribs shaped like butterflies are found in Okinawa. Dugongs were hunted widely 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 the Gulf of Kutch, India, dugong oil is used to preserve and condition wooden boats. Some people there believe dugong meat has aphrodisiac properties.
Dugongs play an important role in the traditions and governance of Indigenous communities in northern Australia. They are part of "sea-country," a living connection between people, animals, and coastal environments. In the Torres Strait and northern Queensland, modern management programs combine traditional knowledge with scientific methods and shared decision-making to protect dugongs.
Conservation
Dugong numbers have decreased in recent years. For a population to stay the same, no more than 5% of adult dugongs can die each year. Humans can only kill 1–2% of female dugongs without risking population loss. This number is even lower in places where dugongs have trouble finding food, which makes it harder for them to have babies. Even in the best conditions, a population is unlikely to grow more than 5% each year, making dugongs vulnerable to overuse. Because they live in shallow waters, they are heavily affected by human activities. Research on dugongs and how humans affect them has been limited, mostly in Australia. In many countries, no one has counted dugongs, so it is unclear how their numbers are changing. The only long-term data comes from the coast of 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 lists the dugong as vulnerable, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora controls and in some areas bans trade involving dugongs. Most dugong habitats are in areas proposed for protection as important for marine mammals. Because dugongs live in many places, cooperation between countries is important. In 1998, Southeast Asian countries supported efforts to protect dugongs. Kenya banned hunting dugongs and limited trawling, but dugongs are not listed as endangered in Kenya’s laws. Mozambique passed laws to protect dugongs in 1955, but these laws are not enforced well. France has a plan to protect dugongs within the Mayotte Marine Natural Park.
Many marine parks have been created along the Red Sea coast of Africa, and the Egyptian Gulf of Aqaba is fully protected. The United Arab Emirates and Bahrain banned all hunting of dugongs in their waters. The UAE also banned drift net fishing and plans to restore coastal ecosystems dugongs depend on. India and Sri Lanka banned hunting and selling dugongs and their parts. Japan listed dugongs as endangered and banned killing or disturbing them. China also banned hunting, catching, and disturbing dugongs. The Philippines was the first country to protect dugongs, but monitoring is difficult. Palau passed laws to protect dugongs, but enforcement is weak, and poaching continues. Indonesia listed dugongs as protected in 1999 and began a conservation plan in 2018. Protection is not always enforced, and dugong products are sometimes sold in Bali markets. Traditional hunters in some areas continue to hunt dugongs, but many struggle to find other ways to earn money. Dugongs are the national animal of Papua New Guinea, where only traditional hunting is allowed. Vanuatu and New Caledonia also banned hunting dugongs. In Australia, dugongs are protected, but rules vary by state, and some areas allow indigenous hunting.
In Queensland, Australia, dugongs are listed as vulnerable under the Nature Conservation Act. Most live in marine parks where boats must travel slowly and mesh net fishing is limited. The World Wide Fund for Nature bought fishing licenses in northern Queensland to reduce harm from fishing. In Vietnam, an illegal network targeting dugongs was shut down in 2012. Concerns have also been raised about potential hunts along Tanzania’s coast.
Even though dugongs are protected in many countries, their numbers are still falling because of human actions, including hunting, habitat loss, and fishing accidents. Many dugongs die from getting caught in fishing nets, but exact numbers are not known. Industrial fishing in deeper waters harms fewer dugongs, while local fishing in shallow areas is a bigger risk. Dugongs cannot stay underwater long, so they are more likely to die if trapped. Shark nets caused many deaths in the past but have been replaced with baited hooks in most places. Hunting was a major problem in the past, but in most areas, it is no longer common, except in some indigenous communities. In northern Australia, hunting has the greatest impact on dugong numbers.
Boat strikes are a problem for manatees, but it is unclear how much this affects dugongs. More boats in shallow waters increase danger. Ecotourism has grown in some countries, but its effects are not well studied. In places like Hainan, ecotourism has caused environmental damage. Modern farming and land clearing have also harmed dugong habitats, and many coastlines are becoming more industrialized with growing human populations. Dugongs absorb heavy metals in their bodies more than other marine mammals, but the effects are unknown.
International efforts to protect dugongs have faced challenges in some developing countries because of political and social needs. Shallow waters are often used for food and income, and aid meant to improve fishing can worsen the problem. In some countries, no laws protect dugongs, and existing laws are not enforced.
Oil spills and land reclamation threaten dugongs in some areas. 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, chemical pollution, and soil erosion. Some Okinawans fought the plan in U.S. courts, citing environmental harm. Later, Japan was found to hide evidence of how human activities, like ship lanes, harm dugongs near Henoko reef. One dugong has not been seen since 2015, when construction began.
If dugongs do not have enough food, they may delay having babies or have fewer young. Food shortages can happen because of habitat loss, poor seagrass quality, or human interference. Sewage, detergents, heavy metals, saltwater, herbicides, and other waste harm seagrass. Activities like mining, trawling, dredging, land reclamation, and boat propeller damage increase sediment, which covers seagrass and blocks sunlight. This is the biggest threat to seagrass.
Halophila ovalis, a type of seagrass dugongs prefer, dies quickly without light and can disappear completely in 30 days. Storms and floods can destroy large areas of seagrass and wash dugongs onto land. Seagrass can take over a decade to recover. Protection efforts focus on limiting harmful activities in seagrass areas, but little is done to reduce pollution.