A Indonesian orang-utan has stunned scientists by apparently using a paste made from plant leaves to heal a wound on his cheek.

It is the first time a wild animal has been recorded treating an injury with a medicinal plant.

A research team in Sumatra’s Gunung Leuser National Park spotted the orang-utan, known as Rakus with a deep wound on his cheek in June 2022. He was later seen applying a plant poultice to the injury.

“First, he fed on the plant for a little while, and then he proceeded to, like, use the juice that the chewing produced to touch his wound with the juice, and then he proceeded to smear the plant mash that he produced from chewing the plant onto his wound and completely plastered the wound, so completely covered the wound,” Caroline Schuppli of the Max Planck Institute of Animal Behaviour told the ABC on Friday.

“After a couple of days, it started closing. And after a couple of weeks, he was observed again and the wound was almost completely healed. You could hardly tell that it was there in the first place.”

Schuppli said the vine, known as akar kuning, was common across South-East Asia. It is considered to have anti-inflammatory and antibacterial properties.

Scientists say the behaviour could come from a common ancestor shared by humans and great apes – and could suggest that medical treatment is older than long thought. Schuppli’s colleague, biologist Isabella Laumer said apes were humans closest relatives

“This again points towards the similarities we share with them. We are more similar than we are different,” she said.

The scientists believe that Rakus knew he was applying medicine because orang-utans very rarely eat the vine, and because of the length of the treatment.

“He repeatedly applied the paste, and he later also applied more solid plant matter. The entire process lasted really a considerable amount of time – that’s why we think that he intentionally applied it,” Laumer said.

The BBC reports that scientists already knew that great apes can use medicine to try to heal themselves. In the 1960s biologist Jane Goodall saw whole leaves in the faeces of chimpanzees, and others documented seeing great apes swallowing leaves with medicinal properties.

But they had never seen a wild animal applying a plant to a wound.

Laumer said it was possible it was the first time Rakus had used such a treatment.

“It could be that he accidentally touched his wound with his finger that had the plant on it. And then because the plant has quite potent pain relieving substances he might have felt immediate pain relief, which made him apply it again and again,” she said.

Or he could have learned the method from watching other orang-utans in his group.

The research was published in the scientific journal Scientific Reports.