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Orangutan spotted treating head wound with medicinal plant
A Sumatran orangutan may have learnt to treat its own wounds with medicinal plants.
While self-medication isn’t unknown in nature, this is the first time a wild animal has been seen applying a plant that has known medical properties to treat an injury.
TW: Image of injury later in article
The history of medical care might go back further than we realised.
While the first records of human medicine are thousands of years old, new research suggests that medicine itself might predate humanity. A Sumatran orangutan called Rakus was seen applying the chewed leaves of akar kuning, Fibraurea tinctoria, a liana with known antibacterial properties, to a facial wound.
This raises the possibility that medical behaviours in apes, including ourselves, may have their origins in a common ancestor that lived millions of years ago.
Dr Caroline Schuppli is the senior author of the paper, published in the journal Scientific Reports.
“The treatment of human wounds was most likely first mentioned in a medical manuscript that dates back to 2200 BC, which included the cleaning, plastering, and bandaging of wounds with certain wound care substances,” Caroline says.
“As African and Asian great apes have also been seen actively treating wounds, it is possible we share a common underlying mechanism for recognising and applying medical substances to wounds. This might have developed in a common ancestor, which may have already showed similar forms of ointment behaviour.”
Blue-headed parrots are thought to use clay licks to counteract the effects of toxins in their food. Image © Andy Wilcock / Shutterstock.
Medical care in nature
The idea that animals can self-medicate isn’t a new one, having existed since at least the 1960s. Known more formally as zoopharmacognosy, it’s thought that a variety of different species might be able to treat their illnesses and injuries to some degree.
Galápagos finches, for example, are sometimes seen rubbing the leaves of the Galápagos guava tree on their feathers. These leaves contain chemicals which repel mosquitos and fly larvae, suggesting the birds might use them as a natural pesticide.
Other birds may even know how to treat an upset stomach. Blue-headed parrots frequently lick clay, which is believed to help adsorb the toxins from unripe fruits they’ve eaten.
Some ants, meanwhile, seem to deliberately eat higher levels of harmful foods when they’re at risk of fungal infection. They don’t eat these toxic foods when the fungus isn’t around, suggesting it might help them to fight it off.
While these are nice theories, it’s difficult to prove whether they’re intentional. Much of the evidence that exists is anecdotal and it’s hard to show how much understanding, if any, an animal has about the substances it’s using.
Even experimental results support these theories, the tests often happen in a lab, so it’s hard to say whether they apply to wild animals.
The best evidence of self-medication generally comes from apes, where long-running behavioural studies give scientists the opportunity to test out their theories. Using decades of observations, researchers can build a case that the apes are using plants or animals for treatment.
One of the most widely accepted self-medicating behaviours is whole leaf swallowing. It’s thought apes swallow bristly, rough leaves to help them expel parasitic worms living in their gut, improving their health.
While it was first seen in chimpanzees, it’s since been seen in gorillas, bonobos and gibbons across Africa and Asia. This suggests it’s likely to be more than just experimentation by the animals, and might have an evolutionary origin.
An even rarer type of self-medication is where apes apply substances directly to wounds. Some chimpanzees place insects into wounds, for example, though the exact reasons what aren’t clear.
But when it comes to Rakus, researchers are more confident that his actions might have a genuine medical benefit.
Rakus the orangutan, pictured two days before applying the plant pulp to his wound. Image © Saidi Agam / Suaq Project.
How do orangutans treat their wounds?
Back in June 2022, the researchers were observing the orangutans that live at the Suaq Balimbing research site in Indonesia when they noticed Rakus. He had a wound on his face, thought to have been from a fight with another male.
A few days later, the researchers saw the ape doing something unusual. Rakus was selectively ripping leaves off an akar kuning vine, chewing them, and applying the juice to his wound. Before finishing, he applied the pulp of the chewed leaves to the injury as well.
As akar kuning is used in traditional medicine in the region, the researchers were aware that Rakus might have been making use of its healing properties. Dr Isabelle Laumer, the study’s first author, explains.
“Akar kuning and related liana species from Southeast Asia are known for their painkilling and fever-reducing effects,” Isabelle says. “Analyses of the plant’s chemical compounds show the presence of alkaloids known to have antibacterial, anti-inflammatory and anti-fungal activities relevant to wound healing.”
The researchers continued to observe Rakus over the following days, finding no signs that the wound was becoming infected. Within five days, the wound had closed and healed completely in the following weeks.
Two months after applying the leaves, Rakus' wound was barely visible. Image © Safruddin.
Though it’s possible Rakus wasn’t intending to heal his injury, the team believe that they have found the first evidence of a wild animal treating a wound with a medicinal plant.
“The behaviour of Rakus appeared to be intentional as he selectively treated his facial wound on his right flange, and no other body parts, with the plant juice,” Isabelle adds. “This behaviour was repeated several times, not only with the plant juice but also with more solid plant material. The entire process took a considerable amount of time.”
The question is now how Rakus may have gained this ability. Though nothing’s been confirmed yet, the researchers have an idea of how it might have been learned.
“It is possible that wound treatment with akar kuning emerged through individual innovation,” Caroline says. “Orangutans at the site rarely eat the plant, but if they accidentally touched their wounds when they were, they would have unintentionally applied the plant’s juice to their wounds.”
“As the plant is a potent painkiller, individuals may have felt an immediate effect, causing them to repeat the behaviour several times.”
While it’s possible Rakus learned this behaviour himself, it’s also possible he learned it from another orangutan. As Rakus’ origins are unknown, it’s currently impossible to say whether this is the case.
In turn, Rakus may be able to pass on the self-medicating behaviour to other orangutans in his current home. These apes have not yet been seen using plants in a similar way, so researchers will continue studying them to find out if Rakus’ abilities catch on.
