Researchers from the Max Planck Institute of Animal Behavior in Germany and Universitas Nasional in Indonesia have documented a rare case of self-medication in a wild Sumatran orangutan. The observation, which involves a male orangutan named Rakus treating his facial wound with a plant known for its anti-inflammatory and analgesic properties, sheds new light on the medical behaviors of wild animals and could offer insights into the evolutionary roots of self-medication.

The study, led by Caroline Schuppli and Isabelle Laumer, took place at the Suaq Balimbing research center in Indonesia, a protected area in the rainforest that’s home to around 150 critically endangered Sumatran orangutans. During daily observations, researchers noticed that Rakus, a male orangutan, had sustained a facial wound, likely from a fight with another male.

Three days after the injury, Rakus selected leaves from a climbing plant, Fibraurea tinctoria, which is known to have anti-inflammatory and analgesic properties and is commonly used in traditional medicine. He chewed the leaves to extract the sap and then carefully applied it to his wound. To complete his treatment, Rakus covered the wound with the masticated plant material, forming a protective layer.

Left: Photos of leaves of Fibraurea tinctoria. Leaf length ranges from 15 to 17 cm. Right: Rakus feeding on Fibraurea tinctoria leaves (photo taken on June 26, the day after applying the plant netting to the wound)
Left: Photos of leaves of Fibraurea tinctoria. Leaf length ranges from 15 to 17 cm. Right: Rakus feeding on Fibraurea tinctoria leaves (photo taken on June 26, the day after applying the plant netting to the wound). Credit: Saidi Agam / Suaq Project

The plant, Fibraurea tinctoria, has a long history in traditional medicine due to its bioactive compounds, including furanoditerpenoids and protoberberine alkaloids. These compounds are known for their antibacterial, anti-inflammatory, antifungal, and antioxidant effects, all of which contribute to wound healing. After Rakus applied the plant’s sap to his wound, there were no signs of infection, and the wound closed within five days.

This unique observation suggests that certain behaviors may be more widespread among wild animals than previously believed. While self-medication through ingestion of specific plants is common in animals, it’s rare to see a wild animal using a plant’s medicinal properties to treat a wound directly. The researchers believe this behavior could have emerged from individual innovation, with Rakus possibly discovering the plant’s analgesic effects by accident and then repeating the behavior because of the relief it provided.

Given that Rakus was not born in the Suaq region, there’s a possibility that this behavior could be observed in other populations of orangutans or even among other great apes. The study’s authors suggest that this treatment strategy might represent an ancient evolutionary trait, indicating a shared common ancestor’s knowledge of plant-based medication.

This discovery of self-treatment with biologically active substances in a great ape is the first of its kind and raises intriguing questions about the evolution of medical behaviors in animals, including humans. The observation also underscores the need to protect critically endangered species like the Sumatran orangutans and their habitats to further explore and understand the complexities of animal behavior.


Sources

Max Planck Institute of Animal Behavior | Laumer, I.B., Rahman, A., Rahmaeti, T. et al. Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan. Sci Rep 14, 8932 (2024). doi.org/10.1038/s41598–024–58988–7


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