Orangutans seek out plants with antimicrobial, anti-inflammatory and wound-healing properties, new research shows.
Based on 20 years of observations of orangutans in Indonesian Borneo, scientists assessed how often the animals ate plants with known medicinal benefits.
The findings suggest orangutans eat combinations of plants in specific sequences - consistent with "self-medication" seen in other species.
It's not clear how they learn to do this, but the researchers think it may involve instinct and/or behaviour passed down over many generations.
"At this stage, we cannot say that orangutans are consciously 'diagnosing' themselves in the same way humans would," said Georgia Allen, who led the study as part of her Masters in Conservation and Biodiversity at the University of Exeter.
"However, our findings suggest they selectively consume certain plants with medicinal properties in ways that go beyond simple nutrition.
"What makes the findings interesting is that some plant species appeared together in the orangutan diet far more often than we would expect by chance.
"Several of these plants are known to contain compounds linked to antimicrobial, anti-inflammatory, or wound-healing effects.
"Importantly, many of these plants are not major parts of the orangutan diet overall, suggesting they may be eaten for specific benefits rather than as everyday food sources."
Chimpanzees are known to engage in "self-medication", for example by eating plants that reduce internal parasite infections. Similar behaviours have also been observed in bonobos, gibbons and gorillas.
The new study used long-term observations of orangutans living in a peat-swamp forest in Central Kalimantan.
Some of the plants eaten by the orangutans are also used by local Indigenous people for medicinal purposes, and the findings highlight the importance of preserving Indigenous knowledge for biodiversity conservation and global health research.
Georgia Allen led the study under the supervision of Dr Kimberley Hockings, and supported by Dr Elodie Freymann.
The study was initiated by Dr Helen Morrogh-Bernard, Honorary Research Fellow at the University of Exeter and Founder of the Borneo Nature Foundation (BNF).
The research used long-term orangutan behavioural data collected through the Orangutan Behaviour Project in collaboration with the University of Palangka Raya - CIMTROP.
The research was made possible with the generous support of the US Fish and Wildlife Service, Great Ape Conservation Fund, the L.S.B. Leakey Foundation, ARCUS, The Orangutan Project (TOP) and Re:Wild.
