They’re one of Earth’s rarest reptiles. But these crocodiles are bouncing back.

Most people would be terrified of entering waters with crocodiles, but not Sao Chan. Like others living in this jungle village, deep inside southwestern Cambodia’s remote Cardamom Mountains, the 73-year-old farmer says the Siamese crocodiles found in the waterways here may look ferocious, but they should not be feared. “If we come close to them, they just run away,” Chan says.

He’s right. There have been extremely few reported attacks by Siamese crocodiles on humans in the world, and reportedly none anywhere in Cambodia. Instead, it’s the crocodiles that have every reason to fear people. Once common throughout Southeast Asia, the notoriously shy Siamese crocodile, which can grow up to 10 feet long, was for decades hunted for its skin and meat to such an extent that, in the early 1990s, the species was thought to be extinct in the wild. The International Union for Conservation of Nature lists the species as critically endangered. 

Some of them survived in the Cardamoms, however, where scattered populations of the reptiles, likely numbering fewer than 200 individuals in total, were rediscovered at the turn of the millennium. Since then, local people have conducted regular patrols to protect them from poachers and other threats. “We believe the crocodiles are sacred,” says Chan, a lead ranger in his area. (Read about 400 baby Siamese crocodiles rescued from the illegal wildlife trade.)

While the patrols and other conservation efforts have helped prevent the extinction of the Siamese crocodiles, concerns about the species’ long-term survival have remained because population numbers have stayed largely flat since their rediscovery.

Now, however, the outlook for one of Earth’s rarest reptiles may finally be improving. In 2022, conservationists have introduced more Siamese crocodiles into the wild than ever before, not just in the Cardamoms but for the first time into a wildlife reserve in the northern part of the country, where the crocodiles historically were found. Advances in genetic testing have streamlined the identification of crocodiles suitable for release, and satellite tracking of reintroduced crocodiles has improved protection efforts.

“We have a long way to go, but the potential comeback of the Siamese crocodile could be Cambodia’s most successful conservation story,” says Pablo Sinovas, who leads the Cambodia program for Fauna and Flora International, one of the nonprofits reintroducing the animals.

Making hybrid crocodiles

Of the two dozen crocodilian species in the world, seven are listed as critically endangered, including the Siamese crocodile. Its decline began with competition from rice farmers for wetland habitat, though it was the commercial hunting to meet the world’s demand for skin-based products and meat that drove the species to the brink of extinction. (See a map of where crocodiles live worldwide.)

Many Siamese crocodiles taken from the wild were initially supplied to croc farms. At their peak in 2010, there were around 900 farms in Cambodia, collectively housing more than 250,000 crocs. But with demand for crocodile skin products dwindling in recent years due to shifting fashion trends and increasing farming costs, the country’s farming business has almost collapsed.

Such conditions have left farmers like Aim Kim San, who runs a small croc farm near the Tonle Sap Lake, on the outskirts of the city of Siem Reap, desperate to sell his farm. “This used to be a very good business,” says Kim, 65, standing on a walkway above a dreary concrete pen packed with some of the farm’s 135 breeding crocodiles. “Now I want to quit and start selling motorcycle parts instead.”

It might seem like a good idea to release unwanted crocodiles from farms into the wild. But farmed Siamese crocodiles have largely lost their genetic distinction because of cross-breeding with saltwater crocodiles and Cuban crocodiles, a species introduced to Cambodia decades ago. This hybridization has made traditionally shy Siamese crocodiles highly aggressive and unfit for life in the wild.

Over the past decade, most of the Siamese crocodiles that Fauna and Flora International has released in the Cardamoms have instead come from a small breeding program the organization runs near Phnom Penh, the Cambodian capital. But breeding Siamese crocodiles is a complicated process, and so far, only about 130 crocodiles have been released in the Cardamoms, with some also coming from farms. 

While this has helped boost the wild population there to an estimated 300 individuals, conservationists want to increase reintroduction rates to ensure the species’ genetic diversity and overall survival. (See pictures of what may be the biggest crocodile ever caught.)

One proven method is to perform DNA tests to identify more genetically pure Siamese crocodiles. Cambodian researchers can now run these tests in the country, rather than sending samples abroad. “This has simplified our work significantly,” says Sinovas, who is also a National Geographic Explorer.

Deploying data and tracking tools

Patrolling efforts in the Cardamoms have also become easier, as illegal logging in the area has subsided due to improved law enforcement and many fewer poachers are targeting crocodiles. But threats persist, particularly from local fishers who may harm or even kill crocodiles while fishing.

Oftentimes, locals appear to strongly welcome efforts to safeguard the crocodiles, especially as conservation spending in the area has helped support new infrastructure, including a Buddhist temple and a school. Villagers are also financially rewarded for reporting sightings of crocodile nests and eggs. “I am happy to report if I see crocodiles in my rice fields, which I did two times already,” says Srey Ny, a 78-year-old farmer, who remembers the time when not only Siamese crocodiles but also tigers were common in the Cardamoms.

Crocodiles released this year in the Cardamoms have for the first time been fitted with satellite trackers. Data shows most of the animals have remained close to their release site.

Researchers have also begun using eDNA technology to detect Siamese crocodiles in the wild. Despite its difficulties, researchers detected environmental DNA left by the reptiles in 19 out of 21 settings. “This could be the starting point of a revolutionary new way of assessing the presence of threatened crocodiles in the wild,” says Sinovas.

Rebalancing ecosystems

Earlier this year, the release of 15 Siamese crocodiles into the remote Siem Pang Wildlife Reserve in northern Cambodia marked the first time that crocodiles have been reintroduced anywhere in Cambodia outside of the Cardamoms.

The release, which was organized by a conservation group called Rising Phoenix, proved challenging, because, unlike in the Cardamoms, locals were wary. Since crocodiles had not been seen in the area for several decades, many residents near the release site were skeptical of having large predators introduced into their local water sources.

Conservationists spent many months trying to assuage concerns. Eventually, they did, and the crocodiles, which had been sourced from a farm and genetically tested, were released into a wetland pool. At first, they remained in a large, wooden enclosure. But the enclosure was designed to break apart under heavy rain, allowing the crocodiles to swim out into wetland channels.

As part of the pilot program, there are plans to release 20 more crocodiles at a nearby site in Siem Pang next year. “Ultimately we want to see a self-sustaining Siamese crocodile population here as part of a healthy aquatic ecosystem,” says Jonathan Eames, CEO of Rising Phoenix.

While the Siamese crocodiles have historically been part of the natural landscape in Cambodia, it’s far from clear what impact their reintroductions will have on fish and other wildlife. “I would be stunned if an apex predator like this was introduced and we didn’t see some dramatic changes in the ecosystem,” says Jack Eschenroeder, a fisheries biologist with the California-based conservation group FISHBIO, who helped survey habitats for the crocodile release in Siem Pang and has conducted some of the eDNA studies.

For his part, Sinovas, of Fauna and Flora International, sees the campaign to rescue the Siamese crocodile from the brink of extinction as part of a larger quest.

“Its survival isn’t just an ecological necessity, but a symbolic imperative if we have any hope of preserving nature on Earth,” he says.

Chhut Chheana contributed reporting from Pur Boeung, Cambodia.

Stefan Lovgren works with the USAID-funded Wonders of the Mekong Project. He and Zeb Hogan are authors of the forthcoming book Chasing Giants: In Search of the World’s Largest Freshwater Fish.