Spoorthy Raman – With its long, pendulous nose, characteristic pot belly and large size, the odd-looking, leaf-eating proboscis monkey (Nasalis larvatus) may not feature on the list of the world's cutest animals. Yet, this endangered primate, a Borneo native living along rivers and swampy mangrove forests, seems to have gained newfound appeal in recent years in the international wildlife trade, according to a study published in the journal Discover Animals.
The researchers searched the internet for media reports of seizures, social media ads and legal trade data from CITES – the international wildlife trade agreement – relating to proboscis monkeys between 1999 and 2024. They found about a hundred individuals in the illegal trade, all from Indonesia. There was a marked uptick in the trade in the last decade, with nearly half of the individuals traded listed on social media platforms such as Facebook and Instagram. In addition, zoos in Indonesia were found to have increasingly acquired these monkeys since 2016, possibly from the wild. The researchers say this surge in trade could have repercussions for the conservation of this endangered species.
Proboscis monkeys are legally protected in all three countries where they are found: Malaysia, Brunei and Indonesia. It is illegal to keep, buy or sell them or their parts. The species is also listed on CITES Appendix I, which prohibits all international commercial trade, except for exchanges between zoos and for scientific research.
While proboscis monkeys have been on study co-author Vincent Nijman's radar since his Ph.D. research nearly three decades ago, he says he never thought of the live animal trade as a threat to the species. "At the time, I was working mainly in Indonesian Borneo, and hunting was a problem, forest fires was a problem, habitat loss was a problem, but the live trade wasn't really a problem," Nijman, who teaches at Oxford Brookes University, U.K., told Mongabay. "The main reason why it wasn't a problem is because everybody knew that you can't keep them alive [in captivity]."
Proboscis monkeys, unlike many primates, do not primarily eat ripe fruits; instead, they feed on leaves and unripe fruits. Their stomach has four chambers with different acidity levels and bacteria, just like cows, to help them digest leaves. Zoos have struggled in the past to procure the leaves they naturally feed on, and hence, maintaining them in captivity has been a challenge.
But in June 2024, the researchers learned that Indian customs authorities had seized a young proboscis monkey, along with 15 birds of paradise and a maleo (Macrocephalon maleo), a large bird endemic to Sulawesi, from a passenger at Mumbai airport, who had arrived from Jakarta.
"It really was a bit of an alarm bell," said co-author Chris Shepherd, who was with the Monitor Conservation Research Society, Canada, when the study was conducted, but is now at the U.S.-based NGO Center for Biological Diversity. "I hadn't seen proboscis monkeys in international trade in the region before, so we decided to look into it further based on that." The current study is a result of that investigation.
An alarming increase in proboscis monkey trade
The researchers found 25 reports in the media linking proboscis monkeys to trade, mostly on seizures, involving 52 individuals over a 25-year period. All of these reports were from Indonesia and none from Malaysia and Brunei, and all but one of the seizure incidents were from the last decade. Most of the seizures were recorded in Kalimantan (Indonesian Borneo), Java and Sulawesi. While 13 reports specifically mentioned trade, three referred to the killing of proboscis monkeys. No media reports mentioned the prosecution or sentencing of anyone involved in the trade.
When the researchers searched Indonesian court records between 2010 and 2025, they found 11 successful convictions for trading or killing proboscis monkeys involving 14 people. Most of these cases involved trade in other protected wildlife such as Sunda leopard cats (Prionailurus javanensis), silvered langurs (Trachypithecus cristatus), the endangered Bornean white-bearded gibbons (Hylobates albibarbis) and birds.
The researchers say these convictions indicate the involvement of commercial traders who deal in a variety of protected species. "It's not one guy in his bedroom that sells a couple of proboscis monkeys," Nijman said. "We see professional businesses with large amounts of legally protected wildlife."
On average, the study found that violators were fined $1,795 and received a sentence of 13 months in prison for their crimes. The researchers say that while the prosecutions in courts are welcome news to curb the illegal trade, the penalties must be in line with the seriousness of the crime and the monetary value of the wildlife traded. The study found that the median fine for violators was just $325, much less than the selling price of a proboscis monkey in the Indonesian pet trade.
An earlier study by Nijman and colleagues on the primate skull trade in Bali had also found proboscis monkey skulls offered for sale to international tourists as souvenirs, despite the species' CITES listing prohibiting international commercial trade. Although the seizure in India is the first known international incident involving the species, Nijman said there's evidence that some of the seized proboscis monkeys in Indonesia were headed to Vietnam and the Philippines, indicating ongoing international trade.
Primatologist Susan Cheyne, vice chair of the IUCN section on small apes who has studied Indonesia's primates since the early 2000s, said that while she was aware of the trade in proboscis monkeys, she didn't realize it was as widespread as the new study indicates. "I have heard stories that proboscis monkeys are hunted for meat or for the bezoar, which is believed to have ... some sort of medicinal property," Cheyne said. Bezoar stones are accumulations of inedible materials found in the digestive tract of various species and used in traditional Chinese medicine.
"It is worrying the number that are in trade because their diet is so specialized that many, many of them are likely dying because they're being given the wrong food," Cheyne, who teaches at Oxford Brookes University, U.K., and was not involved in the study, told Mongabay. "The trade in proboscis monkeys certainly is something that I find confusing because so few people really know what they are."
In addition to being poorly studied, proboscis monkeys in Indonesia are threatened by habitat loss due to agriculture expansion, hunting, forest fires and infrastructure development such as roads and the building of a new capital in East Kalimantan. Only about 9% of their habitat is now under the country's protected areas network. The growing trade in the species is adding to these threats, researchers say.
Questionable zoo trade adds to woes
Zoos around the world have tried to keep proboscis monkeys in the last 50 years with barely any success. In the 1970s, attempts by many reputable North American and European zoos failed due to the primates' specialized diet. By the 1990s, no proboscis monkeys were left in most of these zoos.
However, in 1998, 145 individuals were captured on Kaget Island in Kalimantan as part of a relocation effort prompted by habitat loss – a "stupid decision" according to Nijman – and 61 of them were shipped to Surabaya zoo, which has faced criticisms for animal welfare standards. By the early 2010s, the researchers say 30-45 proboscis monkeys remained in the zoo and by 2023, that number dwindled to 27.
The study collected data from Zootierliste, an online inventory of vertebrates kept at various zoos across the world, to know how many proboscis monkeys are in zoos today. They found that at least 10 Indonesian zoos now house at least 74 proboscis monkeys – a steep increase in the last decade. Prior to 1999, only three zoos, including the Surabaya Zoo, were known to have them. The researchers say it is likely that some individuals from Surabaya Zoo were exchanged with other zoos, while the others came from the wild.
"Many of the zoos in Indonesia aren't striving to be conservation centers. They're more of centers of entertainment, and animal welfare and husbandry standards are extremely low, and therefore turnover is high," said Shepherd, adding that proboscis monkeys are kept to pull in the crowds and bring money. "It's just a novelty."
The Southeast Asian Zoos and Aquariums Association and the Indonesia Zoos and Aquariums Association, which accredit zoos in the region, did not respond to Mongabay's questions on the source of proboscis monkeys in these zoos and their welfare standards in captivity.
Data from CITES show that Japan and China imported 29 live proboscis monkeys from Indonesia for zoo purposes in the last 25 years. Of all the live proboscis monkeys traded on CITES, only one transaction, sent from Indonesia to Singapore, declared the traded monkeys as having been "wild-caught." All the other transactions indicate the individuals as either captive-born (individuals born in a zoo with one or both parents caught in the wild) or captive-bred (individuals born to parents who themselves were born in captivity).
"That's a bit dodgy," Nijman said, referring to the high success in breeding them in captivity as indicated in the transactions. "Well, if you can't keep them alive, it's very difficult for them to get them bred to the second generation."
The researchers also found discrepancies or errors in the CITES data relating to two of the five trades between zoos in Indonesia and China or Japan. The researchers call for all importing and exporting countries to report their transactions accurately to CITES and investigate any discrepancies in data, as they may indicate fraudulent trade.
Online pet trade a growing concern
Indonesia is no stranger to trade in protected species such as orangutans as pets. But in recent years, Shepherd said these mammals have mostly disappeared from physical marketplaces and are increasingly sold online. "Facebook groups [are] where most of these traders operate, and since our study, we've seen many more proboscis monkeys for sale in Facebook groups."
The researchers found at least 48 proboscis monkeys sold online in Sumatra, Kalimantan and Java over the 25-year period, with a surge in recent years. In 2019 and 2020, 11 individuals were listed for sale on the Instagram account of a trader in Bandung, and four were advertised on the Facebook page of a trader in Jakarta in 2024 and 2025, despite Meta's policies prohibiting the online sale of endangered animals on its platforms.
The researchers urge technology companies to enforce their policies and Indonesia to enforce its laws against violators selling proboscis monkeys and other protected wildlife, offline and online, to curb the trade.
"The ones that are for sale are almost all young, and they won't last," Nijman said. "It's a high turnover ... like cut flower markets, but then for very rare flowers." Those dead, he added, are likely replaced by monkeys caught in the wild.
Source: https://news.mongabay.com/2025/07/study-finds-worrying-uptick-in-proboscis-monkey-trade-in-indonesia