Unprecedented numbers of emaciated dugongs have washed up dead along Thailand’s Andaman Sea coast over the past three years, prompting marine scientists to urgently investigate what’s driving their decline.

Thailand’s Department of Marine and Coastal Resources (DMCR) recorded an average 42 dugong (Dugong dugon) fatalities in 2023 and 2024 — more than double the annual losses recorded between 2019 and 2022. The increase seems to be continuing into 2025, with 12 fatalities recorded as of April 9.

Autopsy data reported by the DMCR indicate at least 40% of the deaths in 2024 were likely due to starvation following the widespread depletion of seagrass, the species’ primary food source. In recent years, scientists have recorded concerning die-offs in key seagrass areas along the Andaman coast in provinces including Trang, Krabi and Phuket. Once flourishing habitats full of fish, crabs, turtles and dugongs, many seagrass meadows have deteriorated into barren stretches of sand.

What’s more, cases of dugongs being killed by boat strikes and fishing bycatch have also increased as the animals leave depleted foraging grounds to venture into unfamiliar, riskier waters in search of sustenance.

“When they move to other areas they’re not familiar [with], there are other threats like boat traffic,” Petch Manopawitr, a marine ecologist who’s advising government agencies on the dugong situation, told Mongabay. “Clearly, they’re going everywhere they can to try and find food.”

Aerial survey data also indicate a drop in breeding rates, raising concerns over the long-term viability of the population. “Dugong populations can only survive a very low level of mortality, because they’re such long-lived animals,” Michael Roy, conservation director at WWF Thailand, told Mongabay. With a lifespan of roughly 70 years, they’re slow to reproduce, Roy noted. “Every individual is precious,” he said.

As seagrass specialists, dugongs depend on the availability of healthy coastal meadows. They feed, breed and socialize in seagrass beds, and have a digestive system so adapted to processing seagrass that studies in Australia have shown their gut activity can boost the germination potential of the seeds they eat. Thus, dugongs help to maintain healthy and resilient seagrass meadows, which in turn sustain coastal fisheries and boost global carbon sequestration.

Experts are increasingly concerned at the unprecedented breakdown of this fine interdependency in Thailand. “We’ve never lost so many dugong,” Petch said, noting the mortality rate is “shockingly” high. “If they keep going at this rate, they are going to be extinct in a very short time frame. In a few years at most.”

Thailand had an estimated dugong population of 273 in 2022, according to the DMCR website, with roughly 90% of the animals living along the Andaman Sea coast and the rest in the Gulf of Thailand. Given the hefty losses in recent years, up to a third of this population might already be gone.

Marine specialists say they’re particularly concerned about dramatic seagrass die-offs at Hat Chao Mai National Marine Park and Koh Libong Island in Trang province that sustained more than 75% of the Andaman coast population in 2017. According to DMCR data, between 2020 and 2024, seagrass cover at these sites dwindled by up to 70%.

Milica Stankovic, a seagrass and dugong researcher at Prince of Songkhla University in Thailand, said they first noticed changes in Trang in 2019. “It was very subtle at first,” she said, characterized by a shift in seagrass species composition. Then, in 2021 “there was a massive die off at Libong,” which grabbed the public’s attention. Subsequently, the die-offs spread north to other parts of Trang and then to other provinces.

Kongkiat Kittiwattanawong, a marine mammal researcher at the DMCR, said most of the Trang dugongs have likely either perished or dispersed into nearby provinces, such as Krabi, Phang Nga and Phuket, more than 100 kilometers (60 miles) northwest of their former strongholds. Kongkiat estimated that today, fewer than 10 individuals likely remain in Trang.

Both live and dead dugongs started showing up in other provinces around the time when the seagrass ecosystems in Trang reached critical levels, Kongkiat said. Evidence also suggests some dugong have moved even farther away, entering neighboring Malaysia to the south and Myanmar to the northwest. “We found at least three had died recently in Malaysia, [near the island of Langkawi] where dugong are rarely seen,” Kongkiat said.

Despite the recent population plummet, Thailand remains one of the world’s most significant sites for dugongs, which are protected throughout Thai waters under the National Wildlife Protection Act. Outside of Australia, only six places have dugong populations of more than 100 individuals; Thailand is likely still one of them.

Globally, dugongs are facing the same slew of threats the Thai population are suffering. The species is classified as vulnerable to extinction on the IUCN Red List due to threats such as entanglement in fishing gear, boat strikes, and degradation of their coastal seagrass habitats. These acute threats are compounded by the potential impact of climate change throughout its range, which extends from the western Pacific Ocean to eastern Africa.

Die-off driven by confluence of factors

In January 2025, WWF Thailand organized a gathering of government agencies, scientists and academics to evaluate the situation and meet with communities living close to dugong habitats.

“During the eight-day visit, we engaged with more than 100 people and it allowed world experts and the DMCR to synthesize all the factors that are involved in the dugongs’ decline and consider the possible mitigations,” Roy, the WWF conservation lead, told Mongabay.

While more research needs to be done to probe the underlying causes of the seagrass die-back, the team identified unsustainable coastal practices, climate change, and natural grazing pressure as contributing factors.

The team concluded that acute incidents like dredging river mouths to accommodate larger vessels, as well as chronic stresses like agricultural runoff, have increased silt and nutrient loading in coastal waters, harming fragile seagrass beds.

“When you disrupt the light, typically through sedimentation, you trigger this cascade of impacts [on the seagrass],” Roy said. “It might be at very site-specific level by dredging, or at a seascape level when intense rain events result in rivers discharging more sediment than typical.”

Rising sea temperatures and abnormally low tides that prolong the exposure of delicate seagrass stems have also likely taken a toll, the team found. Mid-2024 saw unseasonably high sea temperatures trigger widespread coral bleaching along Thailand’s Andaman coast, prompting officials to temporarily close several marine national parks to diving and other tourism activities. Like their coral reef counterparts, seagrasses are known to suffer heat stress, although each of the region’s 10 species of seagrass varies in its resilience.

According to Kongkiat from the DMCR, recent tidal anomalies were likely triggered by the co-occurrence of several natural oceanic oscillations, such as the Indian Ocean Dipole and the El Niño Southern Oscillation in the Indo-Pacific. “We found the tidal level at Trang was around 22cm [8.7 inches] lower than the normal tidal range,” he noted.

The seagrass loss is a stark reminder of what can happen when the impacts of local habitat degradation and climate change combine, according to Petch, the marine ecologist. Solutions that center on encouraging sustainable practices will be crucial, he said, given that exacerbating pressures from climate change aren’t going away any time soon.

“We don’t realize that these chronic human impacts — coastal waste water, sedimentation, taking too many species out of the food chain that [boost] ecosystem resilience — all these things are cumulative impacts,” Petch said. “Then when you have one bad year when extreme sea temperature knocks the whole system, it collapses in a very short period.”

Temporary migrations spark conservation challenges

With efforts underway to fix the root causes of the seagrass decline, the DMCR is collaborating with researchers, volunteers and community groups to take emergency steps to save the remaining dugongs.

Their strategy focuses on monitoring the population and establishing temporary marine protected areas around feeding sites, mainly around the island of Phuket, where many dugongs have recently migrated. Before late 2024, dugong sightings were a rarity in Phuket.

“Most people in Phuket have never heard about dugong before,” Petch said. “But with the current situation, Phuket is the last hope for the dugong in Thailand. It’s important to mobilize support there for their long-term conservation.”

Dugongs were first regularly seen around Phuket in November 2024, when small groups began feeding along the coast, fascinating locals and tourists. One group stayed near bustling Rawai Beach for several days to feed on small patches of seagrass. Since then, dugong have been spotted along more parts of the coast and into Phang Nga Bay. However, their spread into this part of the Andaman Sea has experts worried.

“We know there are very few seagrass beds available [around Phuket],” Petch said, noting that the DMCR has attempted to supplement the small migratory population with food normally given to rescued dugong held in aquariums: kale, cabbage and water spinach. However, given a healthy adult dugong eats roughly 40 kilograms (88 pounds) of seagrass per day, supplemental feeding is a stop-gap measure at best. Longer-term solutions that restore natural seagrass beds and address the root causes of the habitat decline are paramount.

“As much as we can do to save dugong around Phuket … we have to think about how we’re going to restore the seagrass in Trang,” Petch said. “That’s the largest seagrass bed that can support the largest [dugong] population.”

Research is already underway to work out how to restore seagrass effectively, but challenges abound, Kongkiat said. “Growing seagrass in stock ponds is quite easy, but [sourcing] seeds [from] seagrass that has declined so much presents a big challenge,” he said, not to mention the difficulty of ensuring the survival of young seagrasses once they’re planted out in the wild. To make restoration a viable option, he said, the problems that caused the die-off must first be solved.

In Phuket, volunteer photographers are also using drones to track dugongs. They gather data on the marine mammals’ distribution, abundance and behavior to help identify where boat traffic and bycatch mitigation efforts are most needed. Similarly, the DMCR’s ongoing necropsy program that investigates the cause of each dugong death also provides vital insights to inform these measures.

In addition to fishing restrictions, go-slow zones are also needed for recreational watercraft, Kongkiat noted: “Jet skis, and even kayaks or paddleboards can be problematic since they can disturb the dugongs when they’re in the seagrass areas so they might not get enough time to feed.”

To ensure the temporary marine protected areas work well, Kongkiat said they’re working closely with local fishers and tourism operators to gain their full support on exclusion zones and netting restrictions. “We’re doing this through a co-management approach rather than declaring forbidden zones,” he said.

Short- and long-term solutions needed

While emergency efforts to protect dugongs that have temporarily migrated to new areas are vital, experts warn that reversing the overall dugong and seagrass declines will take considerable time and resources. As Roy puts it: “This is a long game … it could be 10 or more years perhaps for the population to recover.”

Research in Australia has shown that migrating dugongs will return if their habitat recovers. But tracking this in Thailand will require collaboration across borders, particularly in Malaysia and Myanmar, and in places where dugong haven’t been seen before. To address these knowledge gaps, the DMCR and marine researchers are conducting aerial surveys using aircraft in addition to their drone programs.

There’s also more to learn about seagrass, which experts say can grow at greater depths than previously thought possible in Thailand, representing a potential glimmer of hope. “In the Great Barrier Reef, [seagrasses] grow down to about 75 meters [246 feet],” Len McKenzie, the chief scientist at Seagrass Watch and a member of the expert team assessing the situation in Thailand, told Mongabay.

McKenzie noted that several seagrass species known from Thailand are capable of growing at depth and recommended surveys beyond the usual shallow coastal zones to assess whether dugongs might still be able to survive in Thailand.

With Thailand’s Andaman coast dugongs struggling, the population in the Gulf of Thailand, estimated at roughly 30 individuals in 2022, may come to play a bigger role in the species’ survival. “The Gulf populations are far more important than they used to be,” Roy said. “So we need to do everything we can to maintain and slowly expand those populations and ensure they’re healthy into the future.”

Another cause for hope came in March 2025, when aerial surveys identified 30 dugongs across two sites off the west coast of Phang Nga province. Scientists commented on social media that the group likely comprised resident and migrating individuals. Several dugongs were also videoed mating in a bay in Phuket in late January 2025.

“I’m not sure that the amount of seagrass we have right now can sustain the remaining population,” Kongkiat said, “but at least we will [make] every effort to protect and recover them.”

Banner image: Dugong photographed by drone in Phuket province. Image courtesy of Theerasak Saksritawee.

Carolyn Cowan is a staff writer for Mongabay.

Citations:

Marsh, H., & McKenzie, L. J. (2025). Seagrass and dugongs as indicators of ecosystem health on the Andaman Coast of Thailand: Key findings. Zenodo. doi:10.5281/zenodo.14997358

Lanyon, J. M., Sneath, H. L., Long, T., Blanshard, W. H., Worthy, G. A., & Booth, D. T. (2024). How much seagrass does a dugong need? Metabolic rate of live wild dugongs, Dugong dugon, determined through indirect calorimetry (oxygen consumption). Marine Mammal Science, 41(2). doi:10.1111/mms.13190

Tol, S. J., Jarvis, J. C., York, P. H., Congdon, B. C., & Coles, R. G. (2021). Mutualistic relationships in marine angiosperms: Enhanced germination of seeds by mega‐herbivores. Biotropica, 53(6), 1535-1545. doi:10.1111/btp.13001

Poommouang, A., Kriangwanich, W., Buddhachat, K., Brown, J. L., Piboon, P., Chomdej, S., … Nganvongpanit, K. (2021). Genetic diversity in a unique population of dugong (Dugong dugon) along the sea coasts of Thailand. Scientific Reports, 11(1). doi:10.1038/s41598-021-90947-4

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