New Orangutan Behavior Observed for the First Time

Scientists have spotted an orangutan using medicinal plants to tend to its own wounds.

A male Sumatran orangutan named Rakus was observed by German and Indonesian scientists chewing up the leaves of a plant with medicinal properties and placing the mush onto a wound on his cheek, according to a new paper in the journal Scientific Reports.

This marks the first time that wound-treating behavior has been seen in orangutans and the first time that any animal has been observed using medicinal plants to treat a wound specifically.

Orangutans are the only great apes native to Asia, and are primarily found in the rainforests of Borneo and Sumatra. They are listed as critically endangered, and face several threats, including habitat destruction due to logging, palm oil plantations, and human encroachment.

The plant that Rakus chewed into a pulp is a species called Fibraurea tinctoria, also known as Akar Kuning, Akar Palo, and Yellow Root. Due to its antibacterial, anti-inflammatory, and pain-relieving properties, it is used in traditional medicine by local people to treat wounds. It is also used to treat conditions including dysentery, diabetes, and malaria.

Researchers from the Max Planck Institute of Animal Behavior in Germany and the Universitas Nasional in Indonesia observed this new behavior in June 2022 at the Suaq Balimbing research area in Indonesia's Gunung Leuser National Park. This protected rainforest area is home to approximately 150 critically endangered Sumatran orangutans.

"During daily observations of the orangutans, we noticed that a male named Rakus had sustained a facial wound, most likely during a fight with a neighboring male," study co-author Isabelle Laumer, a primatologist at the Max Planck Institute of Animal Behavior, said in a statement.

According to the paper, Rakus applied the sap from the chewed-up Akar Kuning stem and leaves to his cheek wound repeatedly for seven minutes, then continued chewing on the leaves for around half an hour, before applying the leaf mush to the wound as well.

Afterward, the wound started to heal, with no infections developing. It closed within five days of the leaf mush being applied and was totally healed within a month. The antibacterial, anti-inflammatory, anti-fungal, and antioxidant properties of Akar Kuning may have helped reduce the inflammation of the wound and helped it heal.

"This and related liana species that can be found in tropical forests of Southeast Asia are known for their analgesic and antipyretic effects and are used in traditional medicine to treat various diseases, such as malaria," Laumer said. "Analyses of plant chemical compounds show 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, the fact that Rakus applied the plant paste to only his wound and no other parts of his body, and that it was a continued effort over around half an hour, implies that Rakus was likely treating his wound deliberately.

"The behavior of Rakus appeared to be intentional as he selectively treated his facial wound on his right flange, and no other body parts, with the plant juice. The behavior was also repeated several times, not only with the plant juice but also later with more solid plant material until the wound was fully covered. The entire process took a considerable amount of time," said Laumer.

They note that they are unsure if this was the first time Rakus had used such a method to treat his wounds or if he had learned it from another orangutan.

"It is possible, that wound treatment with Fibraurea tinctoria by the orangutans at Suaq emerges through individual innovation," study co-author Caroline Schuppli, an evolutionary biologist also at the Max Planck Institute of Animal Behavior, said in the statement.

"Orangutans at the site rarely eat the plant. However, individuals may accidentally touch their wounds while feeding on this plant and thus unintentionally apply the plant's juice to their wounds. As Fibraurea tinctoria has potent analgesic effects, individuals may feel an immediate pain release, causing them to repeat the behavior several times."

No other orangutans had ever been seen doing this within the research area, though that may be due to a low rate of encountering wounded apes. Additionally, Rakus may have learned it from others at the location where he was born, which is unknown to the researchers.

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

This is the first time that any animal has been seen applying medicinal plants to wounds. Previous observations of other species have seen chimps applying insects to wounds, eating specific plants for parasitic infections, and rubbing plants on their skin to treat sore muscles, but no other incidences of biologically active plants being used for wound treatment have ever been seen.

The researchers suggest that this behavior—which is reminiscent of human medicine—may have originated in a species that was the common ancestor between humans and orangutans.

"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," said Schuppli.

"As forms of active wound treatment are not just human, but can also be found in both African and Asian great apes, 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."

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