How Many Dugongs Are Left in the World?

Nobody can give you a single, reliable number for the global dugong population, and that uncertainty is itself part of the problem. The species is classified as Vulnerable by the IUCN, with certain regional populations listed as Critically Endangered or Endangered.¹ Estimates cobbled together from aerial surveys across different decades and regions suggest the worldwide total is likely somewhere in the low tens of thousands, with Australia holding the vast majority. But “tens of thousands” carries wide error bars, and the trajectory in most places outside Australian waters is unmistakably downward.

Where Most Dugongs Live

Australia is the dugong’s stronghold, and it is not close. The waters of Queensland, particularly the Torres Strait and the Great Barrier Reef coast, hold far more dugongs than anywhere else on Earth. A systematic aerial survey of Torres Strait in 1987 produced a minimum estimate of roughly 12,500 dugongs in that region alone.² Additional populations stretch along the northern Australian coast from Shark Bay in Western Australia through the Gulf of Carpentaria. Australia likely accounts for the majority of all living dugongs.

The second-largest concentration is in the Arabian Gulf and Red Sea. Aerial surveys in the mid-1980s estimated about 7,300 dugongs in the Arabian Gulf, with herds of several hundred animals photographed off Bahrain.³ A separate estimate put the Red Sea population at around 4,000, with about 2,000 of those in Saudi Arabian waters.³ These Middle Eastern populations are considered globally important but remain data-poor, with much of the evidence coming from feeding-trail surveys rather than direct animal counts.⁴

Scattered populations persist across the Indian Ocean and western Pacific, from Mozambique and Madagascar through the coasts of India, Sri Lanka, Southeast Asia, and the Pacific Islands. Most of these are small, fragmented, and declining. The range map looks impressive at a glance, spanning roughly 40 countries and territories across the Indo-Pacific, but the actual animal density in most of that range is extremely low.

Places Where Dugongs Have Already Disappeared

China provides the starkest recent example of what happens when a dugong population collapses. Researchers surveyed nearly 800 people in Chinese coastal communities and found that only 5% had ever seen a dugong, with the average last sighting reported 23 years earlier. Historical records peaked around 1960 and dropped sharply after 1975. No records exist after 2008, and no verified field observations were made after 2000. The researchers concluded that dugongs are now functionally extinct in Chinese waters.⁵

Okinawa, Japan, tells a similarly grim story on a smaller scale. Researchers reconstructed 125 years of population history and traced a population of roughly 280 to 420 animals in the nineteenth century down to fewer than 100 by 1917, fewer than 70 by 1979, just 11 by 1997, three after 2006, and zero known individuals by 2019. Overhunting caused the initial crash, but after the population dropped below a viable threshold, a declining natural growth rate made extinction inevitable even without further hunting.⁶ The Okinawa case is a textbook example of how long-lived animals can linger for decades after their population has already fallen past the point of no return, creating a false impression that the species is still present when it is actually doomed.

Why We Still Cannot Pin Down a Global Number

Counting dugongs is genuinely difficult. They live in turbid coastal waters, surface briefly and irregularly, and occupy enormous stretches of coastline across developing nations with limited survey budgets. The traditional method uses manned aerial surveys, where observers in small planes fly transects over shallow waters and count the animals they spot. This works reasonably well in clear Australian waters but produces rough estimates with wide confidence intervals. The 1987 Torres Strait survey, for example, reported a standard error of nearly 1,500 animals around its central estimate of 12,500.

Newer approaches are trying to improve precision. Small drones have been tested as a cheaper, more flexible alternative. In one study using unoccupied aerial vehicles over Australian seagrass meadows, researchers produced spatially corrected density models after reviewing over 50,000 images. Their abundance estimates for a single survey area ranged from 47 to 103 individuals across different survey seasons, reflecting both real seasonal movement and the inherent difficulty of getting a snapshot count of mobile animals.⁷ Drones help, but they cover small areas and still require someone to review thousands of images for each survey.

The result of these survey challenges is that the total number you sometimes see quoted for global dugongs (figures around 100,000 appear in older conservation literature) should be treated with serious skepticism. Many populations have never been systematically surveyed, and the ones that have were often counted decades ago. The honest answer is that we know the ballpark for Australian and Arabian Gulf populations, have rough guesses for parts of East Africa and the Red Sea, and are essentially guessing for much of South and Southeast Asia.

A Species Built for Slow Recovery

Even if every threat to dugongs vanished tomorrow, their biology would make population recovery painfully slow. Females typically produce a single calf after a gestation period of about one year, followed by a nursing period that can last at least a year and a half. The interval between calves ranges from three to seven years depending on the population and food conditions.⁸ Dugongs can live for 70 years or more, which helps buffer against short-term dips, but the flip side is that a population reduced to a small size simply cannot bounce back quickly. A dugong population replacing itself at maximum speed might grow by a few percent per year at best. Any sustained mortality above that rate sends the population into decline.

This slow reproduction also means that the proportion of calves in a population is a sensitive indicator of trouble. When researchers see calf ratios plummet, it signals that breeding females are stressed, starving, or dying. In Hervey Bay, Queensland, the proportion of calves dropped from about 22% to just 2.2% after a catastrophic seagrass die-off in the early 1990s.⁹ The Hervey Bay population was estimated to need more than 25 years to recover to its pre-die-off level, and that assumed no further setbacks during the recovery period.

Seagrass Loss Is the Biggest Ecological Threat

Dugongs eat almost nothing but seagrass. They are among the most diet-specialized large mammals on Earth, grazing shallow meadows of fast-growing species and consuming whatever is most available.¹⁰ This means their fate is directly tied to the health of seagrass ecosystems, and seagrass is under threat almost everywhere.

The Hervey Bay event illustrates how devastating a seagrass crash can be. In early 1992, two floods and a cyclone destroyed more than 1,000 square kilometers of seagrass. Eight months later, the dugong population in southern Hervey Bay had collapsed from roughly 1,750 animals to just 71. Most of the missing dugongs had not simply moved elsewhere. Ninety-nine carcasses were recovered, and most of the dead animals were emaciated, having starved over months as the seagrass disappeared. Some desperate animals traveled up to 900 kilometers south before dying.⁹

Climate variability compounds the problem. Across different regions of the Queensland coast, researchers found that calf production declined in association with extreme rainfall events, tropical cyclones, and shifts in Pacific climate patterns, with the effects lagging by one to three years as the impacts rippled through seagrass health and then into dugong reproduction.¹¹ In Torres Strait, episodic seagrass die-backs appear to be natural events that recur periodically, each time suppressing dugong reproduction and forcing animals to relocate.¹² As climate change intensifies extreme weather events, these seagrass-destroying episodes are expected to become more frequent and severe, giving dugong populations less time to recover between hits.

Fishing Gear, Boats, and Hunting

Getting tangled in fishing nets is probably the single largest direct cause of dugong death in most countries outside Australia. Because dugongs forage in shallow coastal waters where small-scale fisheries operate, they are highly susceptible to bycatch in gillnets and other gear.¹³ The conservation threat from bycatch is considered most dire for the small, scattered populations in Africa and Asia where monitoring is minimal and the scale of the problem remains largely unassessed.¹⁴

Australia has taken more aggressive steps than most countries. Re-zoning of the Great Barrier Reef Marine Park eliminated commercial netting from 67% of high-conservation-value dugong habitat, a 56% improvement over previous arrangements.¹⁵ But even with these protections, boat strikes are an increasing concern along urbanized stretches of the Queensland coast, where faster vessel traffic raises the risk of lethal collisions.¹⁶

Traditional hunting adds another layer of complexity. In parts of Australia, Papua New Guinea, and the Pacific Islands, indigenous communities have hunted dugongs for centuries and continue to do so as part of their cultural and customary economy. One study of a remote Australian island community found that dugong hunting remains deeply important to local culture but is facilitated by the economic flexibility that allows hunters to move between subsistence, commercial, and government-supported economic activities. The sustainability of such hunting depends on factors operating at global, regional, and local scales, making it harder to manage than a purely biological question would suggest.¹⁷

Genetic Isolation and the Vulnerability of Small Populations

Not all dugong populations are equally at risk genetically. A study using historical mitochondrial genomes from across the Indo-Pacific found that western populations, particularly those in the Indian Ocean and East Africa, have considerably lower genetic diversity than their Australian counterparts. The researchers argued these western populations deserve additional conservation priority because low genetic diversity limits their ability to adapt to changing conditions.¹⁸

New Caledonia provides a case study in what genetic isolation looks like at its most extreme. Researchers using multiple genetic approaches estimated the effective population size of New Caledonian dugongs at just 95 to 160 individuals. The population showed extremely low genetic diversity and was highly differentiated from Australian dugongs, meaning it is not receiving genetic input through immigration. The researchers suggested an upgrade to Critically Endangered status may be warranted.¹⁹ When your effective breeding population is below 200, random genetic drift and inbreeding can erode fitness in ways that accelerate decline even without any external threat getting worse.

What Dugongs Do for Seagrass Ecosystems

The conservation argument for dugongs is sometimes framed as if they were passive victims of environmental decline, but they actually play an active role in shaping the ecosystems they depend on. Dugong grazing disturbs sediment, removes biomass, and recycles nutrients in ways that can stimulate seagrass regrowth. A recent modeling study estimated that a realistic aggregation of about 700 dugongs could, on average, enhance seagrass productivity by roughly two and a half times and sediment carbon stocks by about two and a half times compared to conditions without dugongs.²⁰ The uncertainty ranges around those figures are wide, but the direction is consistent: dugong grazing appears to boost carbon capture and storage in seagrass meadows rather than depleting them.

This has practical implications for climate policy. Seagrass meadows are increasingly promoted as “blue carbon” assets within national climate commitments, but most carbon budgets for these ecosystems ignore the role of large herbivores entirely. If dugong populations collapse, the seagrass systems they maintain may function differently, potentially storing less carbon. Losing the animal does not just mean losing a species; it may mean losing some of the ecosystem service that makes coastal seagrass valuable to begin with.

The Cautionary Parallel of Steller’s Sea Cow

The dugong’s closest relative to go fully extinct offers an uncomfortable lesson. Steller’s sea cow was a giant sirenian, reaching up to eight meters long, that lived in the cold waters around the Commander Islands in the North Pacific. It was discovered by Europeans in 1741 and extinct by 1768, just 27 years later. Hunting records from Russian expeditions show the animals were killed at more than seven times the sustainable rate, with enormous waste as hunters took what they could carry and left the rest.²¹

The story is more complicated than simple overhunting, though. Genomic analysis suggests that Steller’s sea cow populations had been declining for thousands of years before humans arrived, likely driven by climate changes during the Pleistocene that shrank their coastal habitat and fragmented their range. By the time European hunters encountered them, they were already reduced to a small, genetically impoverished remnant.²² Some researchers have also argued that the loss of sea otters from the fur trade eliminated the kelp forests that sea cows depended on for food, meaning that even without direct hunting, the ecosystem collapse alone could have finished them off.²³

The parallels to modern dugongs are hard to ignore. A large marine herbivore, already reduced and fragmented by environmental change, pushed over the edge by a combination of direct killing and the destruction of its food source. The main difference is scale. Dugongs still number in the thousands, and Australia’s populations remain substantial. But the smaller populations scattered across the Indian Ocean and western Pacific look uncomfortably like the Commander Islands sea cows: isolated groups with low genetic diversity, shrinking habitat, and threats arriving faster than their biology allows them to adapt.