If you’ve ever been lucky enough to wake to gibbons’ song piercing the rainforest fog, you’ll know there are few sounds more haunting on our little planet. The 30-minute songs of these lesser apes – often duets between monogamous lovers – seem to combine musical elements from timber wolves, humpback whales and fire engines. But gibbons are in trouble, facing unprecedented deforestation and a booming illegal wildlife trade, and have disappeared from many parts of their range. One of these places was the world-famous Angkor Wat complex in Cambodia. Yet, thanks to innovative rewildling efforts by conservation group, Wildlife Alliance, the millions of tourists that pass through Angkor Wat every year now have a chance to hear the morning duet of gibbon lovers.

Pileated gibbon mom, Saranik, with her wild-born baby named Spider. Saranik was released into the Angkor Wat forest in 2012 with her partner, Baray. They were the first pileated gibbons to be rewildled in Cambodia. Photograph: Jeremy Holden/Wildlife Alliance

“[The] Angkor Temple Complex, a World Heritage Site, contains some of the oldest forests in Cambodia. However, nearly all of the wildlife that used to live there had been extirpated due to overhunting in the 1980s and 1990s,” said Nick Marx, the director of Wildlife Rescue and Care Programs at Wildlife Alliance. “Though a tragic loss, this means there is plenty of opportunity and space for various species to establish homesteads.”

Wildlife Alliance, partnering with the Forestry Administration and the Apsara Authority, began rewilding the forest in 2013 when it released a pair of pileated gibbons into the forests surrounding Angkor Wat. Less than a year later, the pair had a baby.

“The birth signified the triumph of this unique reintroduction program,” said Marx, who called this trio “a wonderful unit and truly bonded family.”

Since then the team has released another pileated gibbon pair who “took longer to acclimate to the release enclosure...we remained patient as it is vital to give these sensitive animals as long as they possibly need to feel comfortable and exhibit natural tendencies in the wild,” according to Marx.

Male and female pileated gibbons are easily distinguished due to different coat colours – males are largely black while females are white or grey with a black head and belly. Listed as endangered by the IUCN Red List, they are found in Laos and Thailand in addition to Cambodia.

But the Wildlife Alliance team didn’t stop with gibbon families. Last December they released three Germain’s silver langurs into the forest. Known for their wild hair-dos, these monkeys have a special stomach to handle a diet of toxic leaves. Like the gibbons, they are listed as endangered and are killed for food and medicine in addition to losing their homes to agriculture and logging.

“The langur troupe, wary of the gibbons, have moved away from them to the other side of Gate of Ghosts,” noted Marx.

In other words, the new arrivals at Angkor Wat have begun to display natural behaviors even though they were all once victims of Asia’s devastating illegal wildlife trade.

Survivors of a Brutal Trade

The wildlife trade is rife throughout Cambodia as it is in much of Southeast Asia where forests are being emptied of fauna for food, medicine and unsuitable pets. Although there are laws on the books against the trade, corruption, poverty and rising demand across the region have made combating it incredibly difficult.

Gibbons and langurs released at Angkor Wat. Courtesy of: Wildlife Alliance.

Since 2001, Wildlife Alliance has been fighting the illegal wildlife trade via an elite law enforcement squad, dubbed the Wildlife Rapid Rescue Team. But Suwanna Guantlett, the CEO of Wildlife Alliance, said that the NGO quickly ran into the issue of what to do with the the living victims.

“There are several options available - either you can resell them on the black market as many government police do in Southeast Asia, or you can decide to euthanize them, because you have nowhere to put them, or you can decide – as we did – to take care of them responsibly and have a plan for their long term survival.”

The group soon built the Phnom Tamao Wildlife Rescue Centre (PTWRC) to house the rescued animals in natural-like conditions. Today, the facility is home to over a thousand animals rescued from the cook pot or the cage. While most of the animals at the rescue centre are unable to be released back into the wild due to injury or a low chance of long-term survival, a few lucky ones find their way into the forest again.

“[If] they are young, we rear them with minimum human contact so as to reintroduce them back into their natural habitat when they become adults,” said Guantlett. “For those who have been taken as pets into people’s homes and are unfortunately habituated to humans, we place them in stringent de-humanizing conditions where they are able to re-acquire wild reflexes again.”

Marx said that all the individual gibbons and langurs released into Angkor Wat to date were “mother-raised” and had very little contact with people at the rescue centre.

“We only release mother-raised animals so that once in the wild, these animals will be wary of humans and will not be comfortable being close to people,” said Marx, who is the Wildlife Rescue Director at the sanctuary.



But it’s one thing to have animals that could make it in the wild if given a shot, it’s another to find appropriate habitat in a country where many forests already house these species or are on the chopping block.



Angkor Wat is one of the world’s most famous temple complexes. Photograph: Heng Sinith/AP

When the team started looking for a place to rewild their gibbons, the Angkor Wat forest jumped out. Overhunting meant that the forest was free of any big-bodied animals, containing only “minor populations of muntjac, mouse deer, porcupine, northern squirrel and cobras, as well as various bird species,” according to Marx.

But since Angkor Wat became a UNESCO World Heritage Site in 1992, the forest has enjoyed some of the highest protections in a country that lost more than 1.5 million hectares of forest since 2001 - an area half the size of Belgium - according to Global Forest Watch.

“[Angkor Wat] is also a high profile destination with over two million annual visitors,” said Marx. “This means that we can draw attention on a much larger scale to the issues of wildlife and habitat conservation.”

One of the silver langurs released at Angkor Wat. Photograph: Jeremy Holden/Wildlife Alliance

And tourists do have a chance of seeing (and hearing) the rewilded animals – gibbon songs can be heard over a kilometre away – but the proximity also posed a few initial difficulties. Marx said that soon after the gibbons arrived, some guides began using food to try and lure the apes down from tree canopies - where they spend almost their entire life – so camera-wielding tourists could get a closer look. The wildlife team responded by providing supplementary feeding deeper in the forest to draw the gibbons away from crowds.

“This strategy has worked well and the gibbons no longer take food from strangers,” noted Marx.

Future Releases

Given the success of rewilding with both the pileated gibbons and Germain’s silvered langurs, the Wildlife Alliance team is now prepping to bring back its biggest animal yet: sambar deer. The largest deer in Asia, sambar deer can weigh over 500 kilograms and are known as prime prey species for the region’s top predators, including tigers, wolves and dholes. Currently, the Angkor Wat deer are living in an enclosure in the forest getting used to their new surroundings.

Male pileated gibbon released at Angkor Wat. Photograph: Jeremy Holden/Wildlife Alliance

Marx said the team doesn’t intend to stop here, but hopes to rewild the forest with muntjacs, slow loris, leopard cats, peafowl, binturongs and civets. Basically, he said, any “[animal] that will survive well there without endangering either themselves or visitors to the Temples.”

This means Wildlife Alliance has no plans to rewild the area with tigers, elephants, bears or clouded leopards. Not only could such animals pose problems with the throngs of tourists, but Marx said, “the area is not large enough to create sustainable populations [of these species].”

Still, within a few decades the forests of Ankgor Wat could house a faunal community much nearer to what was there when the temples were built nearly a thousand years ago.

“It is far too early to be congratulating ourselves, but we can say ‘so far so good’ and hope for more success and fruitful releases in the future,” Marx said.

But the sound of singing gibbons echoing across the forest today is a testament to the program’s early success – and a unavoidable call for continuing the work.