Orangutan is the first animal observed treating wounds with a medicinal plant

Researchers from the Max Planck Institute for Animal Behavior, in Germany, and the National University of Jakarta, in Indonesia, discovered a previously unprecedented behavior in the animal kingdom: an orangutan using a medicinal plant to treat an injury.

Chimpanzees also try to treat their wounds by applying a substance, but use crushed insects instead of plants. In other words: the orangutan is only the third known species to use some type of substance to treat a wound, and the second to use plants as medicinal tools (the first was, obviously, humans).

The study was published in the journal Scientific Reportsand is the result of observation and monitoring of primates in the tropical forests of Indonesia that has been carried out for some years.

Researchers observed the behavior in Rakus, a male Sumatran orangutan (Pongo abelii)probably in his 30s, and who had first been sighted there in 2009. In June 2022, researchers were monitoring around 150 orangutans in Gunung Leuser National Park, Indonesia, when they saw Rakus exhibit curious behavior.

They saw that the animal had an open wound on the upper part of its right cheek, resulting from Rakus’ fight with another male. Afterwards, they were able to watch the animal collect and prepare a type of paste from the leaves of a climbing plant locally called akar kuning (Fibraurea tinctoria), known for its medicinal ability to treat wounds, relieve pain, reduce inflammation and for having antibacterial and antifungal properties.

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Rakus chewed the leaves and spread the paste with his fingers only on his wound, until he completely covered the injury with leaf pulp. As he did not apply the paste anywhere else on the body, researchers believe this treatment was intentional.

“This case is very special because it is a very powerful healing plant”, says the Scientific American Isabelle Laumer, primatologist at the Max Planck Institute for Animal Behavior and co-author of the new research. “We were unable to observe any sign of infection in the wound, and healing was very fast. After a few days, the wound was completely closed.”

Researchers do not yet know the exact origin of the behavior. Questions still remain as to whether Rakus discovered this wound treatment technique by chance, while eating the plant, or whether it was something learned and passed from one animal to another.

Because male orangutans often disperse from their birth groups after reaching adulthood, researchers don’t know if this was something taught to him while he was in his group.

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Either way, it’s quite a discovery. Chimpanzees have also been observed applying insects to treat wounds, but, according to researchers, these are difficult examples to document systematically. The behavior of Rakus, the orangutan, is also rare, being the only known case to date.

If the use of plants to treat wounds is a common behavior among other orangutans and even other primates, the researchers believe it may indicate a primitive origin of human medical practice in the common primate ancestor.

For now, however, researchers believe it is necessary to continue observational work for a while longer, highlighting the importance of long-term monitoring to draw more solid conclusions.

“We only observe [os orangotangos] for a small part of each individual’s life,” says Laumer. “My project has been in progress for 30 years, and we had not seen this [até então]. This episode just shows how important this type of long-term monitoring is to uncover rare behaviors.”