Orangutan observed using a plant to treat an open wound

Observers have documented several animal species using plants for self-medicating purposes, such as great apes eating plants that treat parasitic infections or rubbing vegetation on sore muscles. But a wild orangutan recently demonstrated something never seen before: It treated its own open wound by activating the medicinal properties of a plant with its own spit. As described in a study published May 2 in Scientific reportsEvolutionary biologists believe the behavior could point to a common ancestor shared with humans.

The discovery took place in a protected Indonesian rainforest at the Suaq Balimbing research site. This region, which is currently home to around 150 critically endangered Sumatran orangutans, is being used by an international team of researchers from the Max Planck Institute of Animal Behavior to monitor the apes’ behavior and welfare. During their daily observations, cognitive and evolutionary biologists noticed a significant injury on the face of one of the local men named Rakus. Such wounds are not surprising among the primates, as they often spar with each other, but three days later Rakus did something the team did not expect.

After plucking leaves of a native plant known as Akar Kuning (Fibraurea tinctoria), known for its anti-inflammatory, antifungal and antioxidant properties, as well as its use in traditional malaria medicines, Rakus began chewing the plant into a paste. He then rubbed it directly on his facial injury for several minutes before completely covering it with the mixture. Over the next few days, the researchers noticed that the self-applied natural bandage prevented the wound from showing any signs of infection or exacerbation. Within five days the injury disappeared before completely healing.

Such striking behavior raises a number of questions, especially how Rakus first learned to treat his face using the plant. According to senior author Caroline Schuppli, one possibility is that it simply comes down to “individual innovation.”

“Orangutans in (Suaq) rarely eat the plant,” she said in an announcement. “However, individuals may accidentally touch their wounds while feeding on this plant and inadvertently apply the plant’s sap to their wounds. If Fibraurea tinctoria has powerful analgesic effects, individuals may feel immediate relief from pain, causing them to repeat the behavior several times.”

(Related: Gorillas like to rack their brains by spinning very quickly.)

If this were the case, Rakus could be one of the few orangutans to benefit from Fibraurea tinctoria. At the same time, adult male orangutans never live where they were born; they migrate considerable distances during or after puberty to establish new homes. So it’s also possible that Rakus learned this behavior from his relatives, but since observers don’t know where he originally came from, it’s difficult to follow that theory just yet.

Still, Schuppli says other methods of “active wound treatment” have also been observed in other African and Asian great apes, even if not used to disinfect or help heal an open wound. Knowing that “it is possible that there is a common underlying mechanism for the recognition and application of substances with medical or functional properties to wounds and that our last common ancestor already exhibited similar forms of ointment behavior.”

Considering how much humans already have in common with their great ape relatives, it’s easy to see how this could be a likely explanation. But regardless of how Rakus knew how to use the medicinal plant, if he ever had to scrap with another male orangutan again, he at least knew how to fix himself up afterwards.