Orangutan in the wild applied medicinal plant to heal its own injury, biologists say

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Armas/Suaq Project

Researchers in a rainforest in Indonesia spotted an injury on the face of a male orangutan they named Rakus. They were stunned to watch him treat his wound with a medicinal plant.

Armas/Suaq Project

When a wild orangutan in Indonesia suffered a painful wound to his cheek, he did something that stunned researchers: He chewed plant leaves known to have pain-relieving and healing properties, rubbed the juice on the open wound — and then used the leaves as a poultice to cover his injury.

"This case represents the first known case of active wound treatment in a wild animal with a medical plant," biologist Isabelle Laumer, the first author of a paper about the revelation, told NPR.

She says she was "very excited" about the orangutan's seeming innovation, which was documented at the Suaq Balimbing research site in the Gunung Leuser National Park in northwest Sumatra, where some 150 orangutans live in a protected rainforest.

The orangutan is named Rakus. Laumer says he might have picked up the large wound in a fight with a rival male. A few days later, he was seen using a plant to treat his injury. The wound then healed, seemingly without any infection.

Laumer and another researcher, Caroline Schuppli, led a team of cognitive and evolutionary biologists from the Max Planck Institute of Animal Behavior in Germany and Universitas Nasional in Indonesia.

What happened?

Around a month after applying medicine to his wound, Rakus has fully healed, with only a slightly noticeable scar. This photo was taken roughly two months after the injury was first spotted. Safruddin/Suaq Project hide caption

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Safruddin/Suaq Project

Around a month after applying medicine to his wound, Rakus has fully healed, with only a slightly noticeable scar. This photo was taken roughly two months after the injury was first spotted.

Safruddin/Suaq Project

Rakus was spotted with the new wound on June 22, 2022. Three days later, he started eating the stem and leaves of a liana — a vine that researchers say the orangutan population in Suaq rarely eats. From there, his behavior grew increasingly intentional and specific.

Rakus spent 13 minutes eating the plant, and then he spent seven minutes chewing the leaves and not swallowing, instead daubing the plant's juices onto his wound. When flies began landing on his wound, Rakus fully covered it with leaf material and went back to eating the plant.

Within five days, the wound had closed. And by July 19 — around a month after the injury was likely sustained — "the wound appeared to have fully healed and only a faint scar remained," the biologists said in their paper, published Thursday in Scientific Reports.

If Rakus was acting as his own nurse, he also seems to have been a good patient: the day after he initially applied the leaves, the orangutan found the plant once again and ate more leaves. He also rested much more than usual, which researchers say likely gave his body a better chance to heal.

What plant was used as medicine?

Pictures of Fibraurea tinctoria leaves, left. At right, Rakus is seen eating more of the leaves one day after applying a plant mesh to his wound. Saidi Agam/Suaq Project hide caption

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Saidi Agam/Suaq Project

Pictures of Fibraurea tinctoria leaves, left. At right, Rakus is seen eating more of the leaves one day after applying a plant mesh to his wound.

Saidi Agam/Suaq Project

Its common name is Akar Kuning (Fibraurea tinctoria). It's a type of liana — a vine that climbs into tree canopies to reach sunshine. The plant has analgesic, antipyretic and diuretic effects; in traditional medicine in the region, it's used to treat diseases from dysentery and diabetes to malaria.

Analysis of the plant's chemical compounds has found "the presence of furanoditerpenoids and protoberberine alkaloids, which are known to have antibacterial, anti-inflammatory, anti-fungal, antioxidant, and other biological activities of relevance to wound healing," according to the researchers' paper.

"It also contains jatrorrhizine (antidiabetic, antimicrobial, antiprotozoal, anticancer, and hypolipidemic properties... and palmatine (anticancer, antioxidation, anti-inflammatory, antibacterial, antiviral properties," the paper said.

So, what does the plant taste like? We asked Laumer if she herself has ever tried it.

"No I have not," she said. "It's rarely eaten by the orangutans at Suaq (in only 0.3% of all ca. 390,000 feeding scans)."

Who is Rakus?

Rakus is a male Sumatran orangutan who is believed to be born in the late 1980s, meaning he was around 32 years old when he was seen applying leaves to his wound. He was first observed in the area in March of 2009.

His self-treatment is exceedingly rare: Researchers say that "in 21 years and 28,000 observation hours," observers at the research station have never seen orangutans using leaves to treat their wounds.

Rakus isn't from the forest where he was seen caring for his injury.

"Orangutan males disperse from their natal area during or after puberty over long distances to either establish a new home range in another area or are moving between other's home ranges," Schuppli said in a news release about the findings.

"Therefore, it is possible that the behavior is shown by more individuals in his natal population outside the Suaq research area."

Nearly two years after his injury, Rakus is thriving.

"He is now one of the dominant males in the research area," Laumer told NPR.

What is 'ointment behavior' and what does it mean?

Rakus chewed leaves and applied them to a wound on his cheek, giving himself medical care. His injury healed without infection, leaving a barely noticeable scar. Armas/Suaq Project hide caption

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Armas/Suaq Project

Rakus chewed leaves and applied them to a wound on his cheek, giving himself medical care. His injury healed without infection, leaving a barely noticeable scar.

Armas/Suaq Project

Rakus' seemingly innovative behavior suggests that "medical wound treatment may have arisen in a common ancestor shared by humans and orangutans," according to the paper.

It's possible that treating a wound with Fibraurea tinctoria began as a fortunate accident, the researchers say, noting that the plant has potent pain-relieving effects and adding that by applying a poultice, the orangutan's main goal may have been to protect his wound from flies.

But because orangutans are believed to keep adding skills into adulthood through social learning, the paper adds, it's possible that the treatment strategy could "also spread socially from individual to individual."

Might Rakus share his medical know-how with other orangutans? That gets into the social question of culture. In the past, orangutans in Sumatra have shown a skill for sharing innovative ideas, with popular behaviors spreading until they reach a natural boundary, like a river.

The findings could lead to new insights into the evolution of self-care and medicine in primates.

Great apes, humans' closest extant relatives, have been documented eating certain plants for therapeutic or anti-parasitic benefits. The researchers also note that in Gabon, chimpanzees have been seen applying small insects to wounds, although, they note, "the efficiency of this behavior is still unknown."

"The treatment of human wounds was most likely first mentioned in a medical manuscript that dates back to 2200 BC, which included cleaning, plastering, and bandaging of wounds with certain wound care substances," Schuppli said in the news release.

Noting that taking action to treat a wound is seen in humans as well as in African and Asian great apes, she added, "it is possible that there exists 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 showed similar forms of ointment behavior."