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An Orangutan Sanctuary in Borneo Is Giving the Endangered Primates a Second Chance, Just When They Need It Most
The critically endangered species gets a helping hand from an Indonesian facility as the island’s human population is about to explode
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The baby orangutans were trying to stall before bedtime. One reached out to grab a particularly long leaf through the bars of its cage, encouraging a human to play, then employed a classic toddler sabotage technique: needing to pee. Eventually, the orangutan relented, climbing up a jungle-gym-like structure in an otherwise empty, if messy, room. The floor was littered with sticks and pieces of wood. The baby orangutan settled into a small hammock and pulled a large leaf over its body as a blanket.
In the wild, orangutans build new nests every night, weaving leaves and branches together and curling up in the tree canopy. But this was not the wild—not quite. This was the site of the world’s largest orangutan conservation organization, the Borneo Orangutan Survival Foundation, or BOSF, based in the Indonesian part of the island (also known as Kalimantan). The day before, I had watched an adult female, standing on a concrete platform on a lush, artificial island surrounded by water, hold a large palm frond over her body to shield herself from the rain. A permanent resident, she was too tame to be released back into the wild and independent enough not to have to live in a cage.
Nearby, a large male conducted high-level negotiations with his keeper, who was trying to get him to eat his carrots before a dessert of dragon fruit. Resplendent in impossibly sleek, long and unmatted orange fur, he poked a stick into the deep water between himself and the keeper. If you don’t give me the dragon fruit now, he seemed to be saying, I’ll just have to come over there and get it myself. Orangutans share 97 percent of their DNA with humans. Somewhere in that missing 3 percent was the transparency of the orangutan’s bluff. The keeper knew that the orangutan couldn’t swim.
Fun fact: What’s in a name?
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If you haven’t been to Borneo, you may imagine it as a land of dense tropical jungle and strange living things—giant flowers, abundant leeches, venomous snakes dangling from vines. In his 1984 memoir Into the Heart of Borneo, the English writer Redmond O’Hanlon described it like this: “Two-hundred-foot-high trees crowded down the slopes of the hills, almost to the water’s edge, an apparently endless chaos of different species of tree, every kind of green, even under the uniform glare of a tropical sun.”
At the time, three-quarters of Borneo was covered in rainforest. Now almost half of that land has been cleared. The view from my plane as I descended was of coal barges fanning out from the coast. The airport is a large, gleaming white-and-silver building with a Dunkin’ Donuts inside the arrivals lounge. But Borneo’s remaining forest has some of the highest species diversity on earth, according to the World Wildlife Fund for Nature, with one area of Lambir Hills National Park, in Sarawak, Malaysia, holding the world record for tree diversity: more than 1,000 species in 125 acres. And each of these holds its own great diversity, too: Scientists have found 1,000 species of insect in a single tree. Overall, Borneo is home to 6 percent of the world’s biodiversity. Nearly 90 percent of all orangutans in the world can be found there. (The rest are on the Indonesian island of Sumatra.)
Because orangutans spend almost all their time up in the trees, the island’s deforestation, mainly from palm oil farming and mining, is the biggest threat they face. Borneo’s orangutan population halved between 1999 and 2015, from 300,000 to 150,000. In the decade since then, the population has declined by another third, to 100,000 today. A 2022 study predicted that more than a quarter of today’s population could be lost to deforestation by 2032.
All of this makes BOSF’s work more crucial than ever. Since the foundation was established in 1991, it has released 533 orangutans, and it maintains 359 permanent residents that are too tame, diseased or disabled to live in the wild. Depending on their circumstances, these residents live in cages or on artificial islands in the foundation’s two centers in East and Central Kalimantan.
There are 20 orangutans with diseases living in one set of tall cages, raised off the ground and set apart from one another. As we approached these cages one morning, a female wanting to get a closer look at us moved down a rope with the agility of a pole dancer. Farther up a sloped pathway was a network of ten silver cages on stilts high above the ground. There, one of the longtime residents, an orangutan named Kopral, who lost both of his arms after being electrocuted and could not survive in the wild, did a forward flip from one end of his cage to the other.
The animals face a formidable new test. Indonesia—the world’s fourth-most-populous country after India, China and the United States—is moving its capital from the sinking island of Java to a planned city called Nusantara, on Borneo, 40 miles from BOSF’s East Kalimantan center. Construction began in 2022 and is scheduled to finish in 2045. The government hopes 1.9 million people will live in Nusantara. By 2035 Indonesian Borneo’s population will grow from 17 million to 20 million.
Indonesia’s government says Nusantara will be a “green forest city,” with all its energy drawn from renewable sources and residents mostly traveling by foot, bicycle or public transportation. The government says the city will be carbon neutral by 2045. Still, it is hard to counteract the environmental impacts of the construction of an entire city in a place where there had only been trees. Last year, workers took a video of an orangutan crossing a construction site for a road leading to the new city. “It would be truly remarkable if such large-scale infrastructure development did not negatively affect threatened species,” Andrew Marshall, a tropical ecologist at the University of Michigan who has studied orangutans in Borneo, told me in an email. “Such projects always do.” He added: “There are good reasons related to human welfare for moving the capital to Kalimantan. It is an understandable move but is likely to have considerable downsides. There are always trade-offs.”
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It takes diplomacy to keep the foundation’s sanctuary going in a place where so many people are struggling. Across Kalimantan’s five provinces, almost two-thirds of the population live below the poverty line. Caring for a single orangutan costs $500 a month, according to Jamartin Sihite, a conservationist and one of BOSF’s trustees. But BOSF’s website invites overseas donors to symbolically “adopt an orangutan” for as little as $10 a month. That’s because local Indonesians, who earn an average of $350 a month, might turn against conservation efforts if they felt that orangutans were earning higher salaries than they were. “They will say, ‘How could you put money to the orangutan, not to us?’” Sihite said. “To make people not look at orangutan as their competitors—this is a part of the strategy.”
What are the traits we share with our large orange relatives? Orangutans treat their wounds with medicinal plants. They make tools and keep their favorites for future use.
But there are many traits we don’t share: Their arms are one and a half times as long as their legs, which helps them climb from branch to branch in what’s known as “quadrumanous scrambling.” They are the most solitary of great apes, a group that includes gorillas, bonobos, chimpanzees and us. When their genome was sequenced in 2011, scientists discovered orangutans have changed very little in the past 15 million years compared with people and chimpanzees.
Orangutans have the longest birth interval of any land mammal: They have a second child only once the first is independent, which takes about seven years. Producing so few young is one reason they struggle to rebuild their populations.
Like humans, female orangutans can get postpartum depression, particularly those who lost their own mothers in traumatic incidents. “When the baby is crying, just because it’s a newborn baby, the mother doesn’t want to hug it, doesn’t want to breastfeed,” Agus Irwanto, one of the foundation’s veterinarians, said. If a mother doesn’t show interest within three days, the baby is taken from her. Depressed mothers don’t seem to notice a baby’s absence.
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Teaching a baby orangutan to survive requires years of close attention. Irwanto laughs when he talks about “jungle school.” The school’s technicians teach the orangutans how to climb, what to eat and how to find it, and how to make a nest. Because orangutans learn by imitation, the technicians act out these activities. The animals tend to bond more with some technicians than others. “They’re picky,” Irwanto said. Trial and error has shown that women are much better at the job. The foundation suspects that it is because, in many cases, the orangutans’ mothers have been killed by men, whose deep voices then scare them.
Once the orangutans graduate, they’re placed on a small, semi-wild island—several acres of land hemmed in by constructed canals. The orangutans must prove that they can be independent. It is time for tough love, which Irwanto sums up in two heartbreaking sentences: “We don’t hug them. We don’t say their name.”
If the orangutans are able to climb, build nests, find food and interact with the other orangutans, they are fitted with telemetric chips and placed in cages for their release. The three release sites managed by BOSF are 12 hours from the sanctuary by car. BOSF researchers spend the next year monitoring the newly wild orangutans. As the animals enjoy their freedom, some of them roam out of the range of radio signals, which means the monitoring team has to search the jungle on foot to find them. The hardest thing about this, one young researcher told me later, is how sore your neck gets from staring up at the canopy.
The building that houses BOSF’s visitors resembles an orangutan (though I was told this was not by design). Three stories tall, it has large arm- and leg-like orange wooden pillars, and it is thatched with a material that has the texture of long, dark hair. That’s the thing about orangutans: Once you have seen one, it is hard not to recognize them in all sorts of things.
During my visit, Aldrianto Priadjati, the habitat’s deputy director, gave a presentation in the open-air dining room. As he began, heavy drops of rain landed loudly on the large, bright leaves behind us. Priadjati changed slides and gestured at the surroundings: tall, thin trees covered in long, tangled vines. On the screen was a photograph of how the land had looked 20 years ago: all grassland with no trees.
In the early 2000s, BOSF began restoring almost 5,000 acres. First, it planted 740 native tree species. Local residents were offered a deal: As long as they helped protect the trees, they could use the land to grow fruit. The fruit trees attracted bats, birds and other animals that spread seeds without the need for more digging. Since then, the foundation has been purchasing fruit from the farmers to feed its animals, which eat more than two tons of it daily. (The land also houses one of the world’s largest sun bear sanctuaries, also run by BOSF.)
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The reforested area was too large to fence. For now, there is something of what Priadjati called a “natural unnatural fence” made up of coal mines. Borneo provides 60 percent of Indonesia’s coal exports. Illegal mining is also rife. Recent estimates of the scale of illegal mining are difficult to find, but in 2014, Indonesia’s government estimated that at least 55 million tons of coal were mined and exported illegally from the country.
For now, most of the land owned or managed by BOSF has been designated a conservation area. Because of BOSF’s success in regenerating forest, the Indonesian government is consulting with the sanctuary on how to redevelop lands around the new capital, which is built largely on rainforest that was cleared for plantations, Sihite said. BOSF is advising the government on which tree species to plant and lobbying for more rainforested land to be legally protected. Still, Marshall, of the University of Michigan, is concerned. “Secondary negative effects of infrastructure development will likely be considerable and spread far from the site itself,” he told me. “Massive projects such as this nearly always have unanticipated consequences.”
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After sunset one evening, I drove to Nusantara with an orangutan researcher named Amanda Rahma. The journey, which should have taken an hour and a half, took almost four hours, as we spent much of it behind slow trucks carrying cement mixers, industrial pipes and water tanks. Forest gave way to low buildings, then suddenly there were tall apartment blocks and a half-finished hospital. Forklifts and bulldozers roamed like dinosaurs after dark.
The dust reminded Rahma of her visits to landscapes destroyed by mines and palm oil plantations, she said. But even she was not immune to the splendor of a city built from scratch. “The Garuda,” she yelled as we drove farther into what had first looked like a construction site. Ahead of us was a giant building shaped like Garuda, a divine eagle from Hindu mythology. It wasn’t finished yet; sparks flew as construction continued late into the night. The light appeared to drip off its outstretched wings like shining feathers.
In April, the foundation released six orangutans into the wild. Three of them had taken more than 15 years to rehabilitate: They’d arrived at the center as toddlers, before the city of Nusantara was a twinkle in the Indonesian government’s eye. By then, I was back home in Sydney, Australia, where my own toddler reminded me of an orangutan more often than I wanted to admit. I kept thinking about the fact that the enormous animals I had seen had changed so little in 15 million years—and yet a city had been conjured from scratch in just three years. In the time it would have taken an orangutan mother to raise two offspring—from 1999 to 2015—half of the island’s orangutans had died.
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This article is a selection from the September/October 2025 issue of Smithsonian magazine