By: Muhammad (Galih) Widiyanto
As fires devoured orangutan habitat in Kalimantan, scientists published studies on the importance of intact forests for the species’ social learning skills.
In Central Kalimantan, at Nyaru Menteng, young orangutans under the care of the Borneo Orangutan Survival (BOS) Foundation had to stop their outdoor activities at the Forest School because, since September 2026, the toxic haze had become thicker and thicker. Exposure to toxic smoke is simply too dangerous for these young apes.
“This is very concerning,” said Anton Nur Cahyo, a primatologist who heads the Borneo Nature Foundation in Palangka Raya. He explained that the “basic principle” of orangutan care, whether at forest schools or in enclosures, is to ensure that each individual’s welfare needs are met. These include maintaining their health and ensuring an adequate food supply.
“The question is whether these rights are being fulfilled, both in the wild and at rehabilitation and reintroduction centres.”
The devastating scale of the forest fires in Kalimantan has decimated these rights. Mongabay reported, as of October 5, 2026, that fires had swept through tropical rainforests that serve as habitats for 13 of the 20 population strongholds of the Bornean orangutan (Pongo pygmaeus). In Tanjung Puting, one of Kalimantan’s key orangutan conservation areas, more than 4,500 hectares of forest had burned.
Indonesia’s Ministry of Forestry reported that 96 Bornean orangutans have been rescued from the wildfires, but threats to their survival persist. In September, a male orangutan was found weak in an oil palm plantation and later died from respiratory complications. Novita, a young orangutan in Bukit Batu, was also found injured, clinging to a sengon tree. Several mother-and-infant pairs were reportedly among the victims of the devastating fires and smoke.
The tragedy is unfolding as a new study on orangutan intelligence is published in the journal Science. The research highlights the crucial role of learning from other orangutans in developing the skills they need to survive in the forest. But the ongoing fires in Kalimantan could have long-lasting consequences for orangutan behaviour.
How orangutans learn
In evolutionary biology, orangutans belong to the great ape family (Hominidae), making them close relatives of humans. Phylogenetic trees show that humans and orangutans descended from a common ancestor. Although the two lineages evolved into distinct species over millions of years, their evolutionary connection makes orangutans an important species to study.
Examining orangutan behaviour — including their cognitive abilities, social intelligence, and processes of learning and knowledge transmission — is one way to understand the evolution of the complex human mind, said Michael Beran, a researcher at the Smithsonian Institution.
Like humans, orangutans learn by observing others, particularly their mothers. But social learning alone is not enough. They must also learn independently through their own experiences, such as exploring the surrounding forest, said Revathe Thillaikumar, a behavioural ecologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany, and lead author of the study.
The combination of social and individual learning, Revathe explained, allows orangutans to acquire a broad range of skills essential for survival, including the ability to recognise and identify different types of food.
When young orangutans are separated from their mothers and natural habitats, “they lose opportunities to independently learn the natural skills that orangutans need, which could ultimately affect their survival.”
The study, conducted by Revathe and eight other researchers, analysed nearly 7,000 behavioural observations of 21 young Sumatran orangutans over their 12-year period of dependency. The researchers focused on two main behaviours: peering, or closely observing another orangutan, and exploration, in which an individual independently attempts to manipulate objects or search for food.
The findings showed that orangutans learned from observing others far more frequently than they initiated exploration on their own.
Exploring a burned forest?
Forest fires such as those that have ravaged Kalimantan over the past three months could disrupt the transmission of knowledge that orangutans need to survive, Revathe said.
Maria van Noordwijk, Revathe’s colleague at the Max Planck Institute of Animal Behavior, previously studied how forest fires affect orangutan behaviour at the Tuanan Research Station in Central Kalimantan following the 2015 fires.
Her research found that fruit production in the forest declined dramatically for 2.5 years after the fires. The shortage was thought to be linked to the disappearance of pollinating insects and reduced photosynthesis in plants due to smoke exposure.
As food became scarce, orangutan behaviour changed. Female orangutans travelled shorter distances and spent more time resting. Food shortages also intensified competition among individuals, often triggering conflicts.
“Animals who lost their homes had to move, and those that didn’t had to accept more crowding,” says Maria in a press release issued by the Max Planck Institute of Animal Behavior on October 28, 2026. “Everybody was affected.”
She also noted that no pregnancies were recorded in the population she studied during the 2.5 years following the fires. Even mother orangutans spent less time with their offspring. “So, fires impact the animals months or even years after the flames have been put out,” van Noordwijk says.
“That loss will translate into many of the same pressures documented after the 2015 fires,” says van Noordwijk. “At the same time, I’m afraid that the toll will be worse than last time.”
Maria fears that the impact of this year’s fires on orangutans could be even more severe than what she documented in 2015. “That loss will translate into many of the same pressures documented after the 2015 fires,” Maria. “At the same time, I’m afraid that the toll will be worse than last time.”
Revathe stressed the importance of protecting orangutan habitats, noting that healthy, intact forests are essential for orangutans to acquire the knowledge and skills they need to survive.
Meanwhile, back in Kalimantan, Anton has been planting tree seedlings on burned land.
“Perhaps we ourselves need to be the ones to nurture hope,” he wrote in a social media post.
*) Muhammad (Galih) Widiyanto is an Indonesian Science Affairs Fellow 2026. He is also a Jakarta-based popular science writer. He holds a bachelor’s degree in physics from Brawijaya University and a master’s degree in Science Education and Communication from Utrecht University.
Previously, he worked as a managing editor at Kok Bisa, an Indonesian science media platform, where he produced popular science content and organised public discussions. He is interested in how knowledge is produced, communicated, and consumed in society.
First published in Indonesian Science Affairs
