Carolyn Cowan, Medan, Indonesia – Two infant siamang gibbons cling to each other. Barely 6 months old, their lanky limbs entwine their tiny bodies as they stare out of the triage cage, their wide eyes shining. Each is an orphaned victim of the illegal pet trade.
Like most trafficked gibbons, their mothers were likely shot and killed by poachers before they were wrested from her body and shipped into the trade. Deprived of maternal body heat and milk, the youngsters now instinctively grip each other as if for comfort.
At the back of the rescue enclosure, a smaller body hunkers in a corner, shrouded in solitude and silence. A tiny Javan gibbon, it glances up from time to time, but is wary.
"The Javan gibbon is still shy," says Sinan Serhadli, support officer at the gibbon rehabilitation and release program run by the Orangutan Information Centre (OIC) as part of the Sumatran Rescue Alliance (SRA) in Indonesia's North Sumatra province. "He will eat, but he doesn't want any contact with humans."
The infant siamangs (Symphalangus syndactylus) and Javan gibbon (Hylobates moloch) were brought to the SRA rehabilitation center on the outskirts of Gunung Leuser National Park in March 2025 after an Indonesian naval patrol confiscated them from a boat intercepted in the Strait of Malacca. The vessel, believed to be destined for Peninsular Malaysia or southern Thailand, was smuggling dozens of wild animals in cramped and unsanitary cages.
Of the 16 gibbons reportedly aboard that voyage, only the three infants at the SRA rehabilitation center survived. The 13 other gibbons either perished during the crossing or died at the rescue center, despite the best efforts of the veterinary team.
"Those babies [were] in a nightmare condition," Sinan says, recalling the gibbons that died upon reaching the center. "Two of them had maggot-infested wounds – bullet holes."
The bust was part of a growing trend in gibbons trafficked internationally, driven largely by demand for babies as pets and fueled by social media content portraying them as "cute" companions. But trafficked gibbons undergo immense suffering, and the trade is pushing already threatened species ever closer to extinction.
Gibbons, famed for their graceful agility high in the forest canopy, are captured from the wild by poachers who shoot the mother to get to her young after her body crashes to the ground. Cases of infant gibbons with pellet gun wounds sustained during such confrontations are all too common, Sinan says.
Baby gibbons that survive the fall from the canopy subsequently suffer a horrific ordeal as they're bundled into bags or cages and transported for days in increasingly unhygienic conditions without food, water or medical care, causing them to grow weak and their wounds to fester. Those that make it to their end destination alive will likely be deeply traumatized.
"Most gibbon babies die – that's the sad reality," Sinan says. "Probably only one in 10 actually makes it to an end buyer. But the traffickers take that into account, right? They calculate losing about 80-90% of them."
What's more, for every baby gibbon smuggled, it's not just the mother that dies. Her death disrupts the complex social structures gibbons live in, meaning any dependent juveniles in the family group are also likely to perish, and solo adults may have difficulty defending their territory. As Sinan puts it: "The waste is enormous."
Escalating transnational trade
While habitat destruction remains a major threat to wild gibbon populations across their 11 range countries, from India to Indonesia, the illegal trade is rapidly catching up as a primary threat in many regions.
Seizures hit an all-time high in 2025, according to TRAFFIC, an international NGO that monitors the wildlife trade. At least 336 gibbons were confiscated across South and Southeast Asia between 2016 and 2025, with 65 of those seized in just the first eight months of 2025.
The black market for gibbons has long existed in countries like Indonesia and Vietnam, where they're prized for their whooping calls and their appeal as a status symbol. Almost two-thirds of gibbon seizures during the decade up to 2025 were in Indonesia.
However, the past two years have seen a shift in smuggled gibbons destined for India and the UAE, according to the TRAFFIC analysis.
Recent seizures of gibbons at major airports and border crossings indicate India in particular is emerging as a key destination, reflecting a growing appetite for exotic pets in the country. A separate 2023 report by TRAFFIC cited 56 seizures of nonnative wildlife entering India in 2022 alone, involving nearly 4,000 animals, including more than 100 primates.
Observers also point to the role of large zoos and private collections in India in stoking demand for primates, with multiple investigations linking such facilities with exotic wildlife from across the world turning up in the country.
Richard Moore, senior adviser at International Animal Rescue, an NGO known by its Indonesian acronym YIARI, says social media and the rising popularity of urban "mini-zoos" is partly behind the surging demand for gibbons. "Small venues – cafes, villas, private 'zoos' – use animals like gibbons as drawcards for social media and paying visitors," he wrote in an email.
Indonesia, Malaysia and Thailand serve as both source countries and transit hubs. Cases of infant gibbons stashed in suitcases and smuggled by air between Thailand, Malaysia and India suggest traffickers are becoming increasingly brazen in their attempts to move the apes across borders to meet growing demand.
In one incident in May, authorities discovered seven dead gibbons in the possession of two people at a hotel in Mumbai. They had arrived from Malaysia with nine primates concealed in their checked luggage. Another case in October involved an airline passenger arriving in Mumbai from Thailand who was smuggling two Javan gibbons, one of them dead, in their baggage. The passenger reportedly claimed that a member of a wildlife trafficking syndicate had given them the animals to deliver in India.
The prevalence of infant gibbons discovered in the trade in Indonesia is particularly eye-opening, Moore says. YIARI's analysis of online trade and seizure records since 2015 shows that an average of 130 gibbons are traded annually across the country, he says, roughly 90% of which are juveniles or infants captured from forests in Borneo, Java and Sumatra.
The true scale of the trade is likely far worse than such analyses indicate. "Due to its clandestine nature, much of the trade remains hidden," Moore says. "We still don't know [how] many animals die before reaching buyers. And while India appears prominent in recent cases, the scale, buyer profiles, and any onward movement to secondary destinations remain poorly documented."
What is crystal clear to Moore, however, is the unsuitability of gibbons as pets: "Gibbons are territorial, [they] bite, and scream, require large, sturdy enclosures and specialised care, and can quickly become dangerous in a household."
Housing the victims of trade
More trafficking means more rescued gibbons in need of care, raising concerns about where they can all be housed. The number of facilities equipped to nurture the small apes has grown from 16 to 23 over the past five years within gibbon range countries, even in locations like Bangladesh where trafficking historically wasn't an issue.
"In an ideal world, there wouldn't be a need for any rescue centers, because we'd have stopped the trade," says Susan Cheyne, vice chair of the primate specialist group section on small apes at the IUCN, the global wildlife conservation authority. "But we're not in an ideal world."
Therefore, ensuring wildlife authorities know where to send confiscated gibbons so that they can have the best chances of being rehabilitated and eventually returned to the wild is vital, she says.
But most gibbon rescue centers are already at capacity. "This is not sustainable in any way, shape or form," Cheyne warns.
The SRA facility in North Sumatra has been caring for gibbons rescued from the trade since 2021 and currently shelters 25 gibbons from three species native to Sumatra and Java, all categorized as endangered on the IUCN Red List. "Our rescue center is receiving more and more – we can't take them all," Sinan says. "That's why we want to focus on release and prevention of trafficking."
Siamangs – the world's largest and loudest gibbon and a species confined to Sumatra, Peninsular Malaysia and southernmost Thailand – dominate the illegal trade. They account for roughly 70% of the small apes at the SRA facility, Sinan says. The center's other residents include agile gibbons (Hylobates agilis), found in Sumatra, and Javan gibbons, a species now confined to shrinking forest fragments in Java, where only 4,000 are thought to remain in the wild.
The toll of the trade is clear at the SRA center. While some gibbons are being prepared for release back into the wild, others are so behaviorally scarred by their time in the trade and captivity they will likely never be able to return to the forest.
Many have suffered horrific physical injuries and psychological trauma. As intelligent animals, mental scars from their ordeal in the trade – from seeing their mother killed and being torn from her body, to adult gibbons kept isolated in cramped apartments or cages – are long-lasting. Many display abnormal behaviors in response to their past trauma that can further complicate the rehabilitation process.
Ochi, an adult female agile gibbon, incessantly displays mating behavior, for instance, thought to be an anxiety response developed during her past captivity away from other gibbons. Jack, a juvenile agile gibbon, has an air rifle pellet embedded between his eye socket and skull that veterinarians say would be too risky to remove. And a young female siamang, named Koko, came to the center with an injury so bad her left hand had to be amputated. "She can still hook her wrist around objects to swing, so we're confident she can be released in the future, when she's ready," Sinan says.
Femke den Haas, co-founder of Jakarta Animal Aid Network (JAAN), which operates seven wildlife rescue centers across Indonesia, says their South Sumatra and Java facilities have seen similar influxes of gibbons. The two centers have taken in a record 36 confiscated gibbons in the past 18 months, most of them babies. "The numbers have been quite crazy," she says. "It's very concerning."
JAAN deploys a team of sniffer dogs at Indonesian ports and airports to intercept wildlife smuggled between islands. It also provides intelligence to authorities, working as part of a coalition of NGOs that includes OIC and YIARI to support seizures and arrests.
Most of the gibbons intercepted by JAAN's teams are siamangs, den Haas says. However, Javan gibbons are increasingly confiscated in Sumatra, she notes, reflecting the island's dual role as both an end destination for domestic gibbon trafficking and a hub for traffickers exporting animals internationally via its well-developed road and port networks.
A heavy loss
It will be at least six years before the two siamang youngsters rescued from the March 2025 incident can be considered for release back into the wild, Sinan says. Meanwhile, once the Javan gibbon is stronger, it will have to be repatriated to Java so that it can be prepared for release in its native habitat.
For now, the two siamangs are learning to climb and forage for food by attending what Sinan calls "jungle school" – an obstacle course in the center's grounds comprising trees, ropes and feeding buckets to train young gibbons' wild instincts. Then, when they're mature enough, they will need to be paired with compatible mates.
Gibbons typically live in monogamous pairs, so pair bonding is a vital step in their rehabilitation. Releasing family units rather than individuals minimizes the problem of lone males initiating violent confrontations with wild gibbons upon release, and pair bonding increases the chances of them staying together and successfully defending a territory, according to the IUCN.
Pairing can be a lengthy process of trial and error, requiring meticulous observations of the gibbons' behavior toward one another. At the SRA facility, enclosures connected by short tunnels enable keepers to test the compatibility of pairs before they're allowed to be together in the same space. Once they have mated and produced offspring, the family is ready to be considered for release.
The SRA center released its first paired family in July 2025 within a newly reforested patch of reclaimed oil palm plantation in the buffer zone of Gunung Leuser National Park, not far from the rehabilitation center. The pair, named Bejo and Mesra, had produced a baby and were strongly bonded. However, things didn't go according to plan.
While the release site had passed initial evaluations for a range of criteria, such as food availability and the absence of existing gibbon populations, monitoring teams observed the adult male abandon the family several weeks after the initial release – likely driven away by wild males not previously recorded in the area. Roughly 10 weeks after the family's release, Mesra and her baby perished, despite the best efforts of veterinary teams.
The loss of the gibbon family was a heavy blow to the SRA team, who are readying three more pairs for release over the coming year. Their biggest challenge will be locating suitable release sites that have adequate forest cover yet have no existing wild gibbons.
According to Sinan, the situation underscores how the release itself can never be the end goal of gibbon rehabilitation programs. Rather, stopping the trade so that gibbons are not taken from the wild in the first place has to be the overall objective.
"Rehabilitating gibbons endlessly doesn't really address the issue well," he says. "The most important thing is addressing the wildlife trade."
Gibbons pass under the radar
Indonesian law provides a maximum penalty of 15 years' imprisonment for anyone who transports, trades, keeps or kills a protected species, such as the nine species of gibbon found in the country. But legal loopholes, online trade and weak enforcement mean prosecutions are few and gibbons continue to be captured.
The surge in gibbon seizures in North Sumatra province was the main motivation for the OIC, which previously focused more on orangutans, to set up its gibbon rehabilitation and release program at the SRA center. The lack of a specialized facility meant confiscated gibbons were previously sent to local zoos that lacked the expertise to prepare them for reentering the wild.
"Sometimes, when our rescue team had gibbons in our hands, we were asked to send them to the zoo," Panut Hadisiswoyo, founder of the OIC, tells Mongabay at his office in Medan, the provincial capital. "We were fed up and frustrated about this. It meant we didn't want to rescue gibbons." Housing trade victims in zoos not only consigns the animals to a life in captivity, it does nothing for wild populations, Panut says, ultimately weakening the forest ecosystems authorities are meant to protect.
The practice of sending confiscated animals to zoos has also come under fire from conservationists who argue it risks the animals disappearing back into the trade via unscrupulous facilities. Several zoos in North Sumatra have a poor track record, according to Panut, with animals being trafficked again or randomly set free in the wild, resulting in gibbons wandering plantations or villages, unable to fend for themselves.
The SRA center has the capacity to care for up to 30 individuals – still well below the number seized by authorities, but better than nothing. A remaining challenge is that the gibbon trade is typically viewed by authorities as less heinous than that of higher-profile species, such as orangutans. "Gibbons have less attention," Panut says. "Maybe for orangutans, people think twice, [but] the government doesn't give [gibbons] priority."
In a country like Indonesia, sometimes authorities themselves are involved. Panut recalls finding an adult siamang held captive in a cage in a police compound while he was collecting a seized orangutan to move it to a rescue facility. The officers told him they liked its singing.
According to an analysis of wildlife crime cases in Indonesia between 2016 and 2021 by YIARI, gibbon cases involving one or two animals are frequently dropped. When prosecutions do proceed, sentences are generally light, with fewer than four cases of gibbon trafficking reaching prosecution each year during the study period. The harshest sentence recorded during that time was 21 months' imprisonment and a fine of $1,800.
"There's been a clear uplift in government awareness and willingness to act on illegal wildlife trade in recent years," Moore says. However, "operations frequently net couriers or temporary handlers while organizers evade arrest and charging."
With law enforcement often underresourced, international cooperation to stem cross-border trafficking and bring smugglers and overseas buyers to justice is crucial, observers say. "Governments should really start to collaborate and not just focus locally," den Haas of JAAN says. "We won't see this ending before we really have a very powerful collaboration between all the countries [involved]."
Kanitha Krishnasamy, director for TRAFFIC in Southeast Asia, says each seizure should be treated as an opportunity to investigate criminal networks. "Who is commissioning the poaching and trafficking, and who are the ultimate recipients?" she says. "It's time to move beyond only focusing and penalizing low-level middlemen that are treated as the cost of doing business, when the real masterminds continue to pilfer and profit."
Back at the SRA rehabilitation center, gibbon keeper Iqbal Suny watches over the two infant siamangs at jungle school. Constantly clinging to each other, they clumsily explore tree branches, nibble leaves and collectively dangle their eight limbs from ropes.
Their pathway back to the wild will be long – it could take up to 10 years to pair them successfully and locate a suitable release site. And with the shadow of the loss of the first gibbon family released in North Sumatra cast over them, the team are aware of a hard truth: once a wild gibbon is removed from its natural forest habitat, its future is anything but certain.
But with the illegal trade ramping up, every gibbon eliminated from the wild is a serious blow to already endangered populations. Gibbons are slow to reproduce. Females reach sexual maturity at between 6 and 9 years, and typically have a single baby at most every two to three years. Therefore, the impact of the trade will affect their numbers for years to come.
Sinan says the window of opportunity to prevent critical future population declines is now: "You can't wait until they're critically endangered [before taking] conservation action," he says. "It's hard to bring back species once they've lost genetic diversity and have low population numbers."
Despite the challenging, costly, and at times harrowing process of rehabilitating gibbons, striving to put them back into the wild, he says, is simply "the right thing to do."
Banner image: Trafficked infant siamang gibbons confiscated in North Sumatra photographed in March 2025, one of which subsequently perished. Image courtesy of Jason Savage Photography.
[Carolyn Cowan is a staff writer for Mongabay.]
Citations
Cheyne, S. M. (2007). Unusual behaviour of captive-raised gibbons: Implications for welfare. Primates, 48(4), 329-329. doi:10.1007/s10329-007-0058-x