Orangutan treats wound with plant

No-one saw what caused the nasty gash on Rakus’ face. Although, given he was a newly matured male orangutan, primatologists can hazard a good guess: he had been fighting.

What they did see was Rakus, who lives in the Sumatran jungle, start eating a plant that orangutans almost never eat. He kept chewing a liana plant methodically, taking the juice from his mouth and applying it to the deep wound. Then he packed the wound with chewed leaves.

“It was almost like a plaster,” said Isabelle Laumer, from the Max Planck Institute of Animal Behaviour in Germany. And, just like a plaster, it seemed to help the gash to heal. After just a few days, to the scientists’ surprise, the wound had closed.

Local healers would not be surprised: the liana plant has long been used in traditional medicine and several studies have validated its effectiveness as an antibacterial, antifungal and anti-inflammatory agent.

This makes the observations of Laumer and her colleagues, recounted in the journal Scientific Reports, the first recorded sighting of a wild animal treating a wound with a proven medicinal plant.

Laumer said they could not be sure where the behaviour came from. Male orangutans move to new areas as they mature so it is possible that Rakus had learnt a practice from elsewhere in the jungle. Equally, he may have discovered it himself. “Maybe it was accidental,” she said. “Maybe he touched a finger to the wound. Because the plant has quite potent pain relieving substances he could have felt immediate pain relief, and so repeated the action.”

Although this is the first time that primates have been observed using proven medicines to heal wounds, the behaviour is not wholly unexpected.

In 2022, researchers spotted chimpanzees catching insects and rubbing them into cuts and grazes. Without being able to find out which insects they were using, it was impossible to judge the efficacy. Even so, the chimpanzees seemed to believe it worked.