A Sumatran Orangutan in Indonesia has been observed healing a nasty wound on its face by making a paste from a native plant known to locals as having healing properties.
The primate chewed the stems and leaves of the Akar Kuning plant (Fibraurea tinctoria), a type of liana vine, and repeatedly spread the juice and shredded leaves on his open wound over a number of days.
Traditionally, the plant has been used by Sumatran islanders as an anti-inflammatory, anti-fungal and anti-bacterial medication. But this was an almost unique observation of a wild animal of any species seeking out a specific plant to cure an injury.
Although there are recorded instances of primates in other parts of the world swallowing whole leaves and nibbling bitter pith, as well as rubbing their fur with medicinal foliage, to medicate against parasites or perhaps alleviate muscle pains, until now there has only ever been one isolated report of wound treatment with plant material.
The orangutan, a male about 35 years of age, known as Rakus, lives in the peat swamp forests of Gunung Leuser National Park on the island of Sumatra in the Indonesian archipelago.
A research team in the Park noticed in June 2022 that Rakus had a large open wound on his facial flange, or cheek pad, close to his right eye, that looked swollen and infected. They assumed it must have been the result of a fight with a rival male, as Rakus had become sexually active less than a year before. He had been heard ‘long calling’ in previous days in an effort to assert dominance.
About three days after he received the wound, Rakus was seen chewing the leaves of the plant and smearing the juice from his mouth over the raw patch. When flies settled on the wound, he spat out some leaf mash and spread it over the painful area until it was completely covered.
He repeated his treatment regularly over the next few days, and also rested more than usual. This behaviour and the frequent re-application of the poultice to the wound removed doubt that Rakus’ actions were accidental. What is also known is that orangutans rarely eat that particular plant, so its choice would seem to have been deliberate and related to dealing with the injury.
Eight days after the wound was first noticed, scientists could see that the raw skin had completely closed up and months later there is now barely any scarring left to show where the orangutan was injured - see below.
Whether Rakus was using the plant because he was conscious that it would help to heal his wound, or because he was copying what he had seen other orangutans doing with their wounds, is still the subject of debate amongst researchers. The Akar Kuning plant has pain-relieving properties so Rakus may have accidentally touched the plant in the past and noticed that it soothed a sore finger, for instance.
The orangutans in the study area are well nourished and generally peaceful so not many of them sustain wounds as bad as Rakus’. This has made it difficult for scientists to establish if other members of the species in the area also self-medicate their injuries. Researchers’ efforts are now focussed on gathering more information on this aspect of orangutan behaviour.
Overall, the study adds to the knowledge scientists have been gathering around the world about the origins of human wound care and whether the use of medicinal plants was behaviour learned by our ancient ancestors from observing their closest primate relatives
Research published in the Open Access Scientific Reports
Main image: Rakus feeding on Fibraurea tinctoria leaves (photo taken on June 26, the day after applying the plant mesh to the wound). Credit: Armas / Suaq Project
