Primatologists in Indonesia have observed a wild male Sumatran orangutan (Pongo abelii) who sustained a facial wound. Three days after the injury he selectively ripped off leaves of a liana with the common name Akar Kuning (Fibraurea tinctoria), chewed on them, and then repeatedly applied the resulting juice onto the facial wound. As a last step, he fully covered the wound with the chewed leaves. This behavior presents the first systematically documented case of active wound treatment with a biologically active plant by a wild animal and provides new insights into the origins of human wound care.
Process of wound healing: Rakus fed on and later applied the masticated leaves of Fibraurea tinctoria to his facial wound on June 25, 2022. On June 26 he was again observed feeding on Fibraurea tinctoria leaves. By June 30 the wound was closed and by August 25 was barely visible anymore. Image credit: Laumer et al., doi: 10.1038/s41598-024-58988-7.
In the early 1960s, the legendary primatologist Jane Goodall first described the presence of whole leaves in the feces of chimpanzees (Pan troglodytes) at Gombe Stream, Tanzania.
By the 1990s, this behavior — now called whole leaf swallowing — was documented at several African great ape study sites, along with bitter pith chewing, and demonstrated to have therapeutic, anti-parasitic function.
Since then, various forms of self-medication have been observed in wild great apes.
In June 2022, Max Planck Institute of Animal Behavior researcher Isabelle Laumer and her colleagues observed a male orangutan in the Suaq Balimbing research area in Gunung Leuser National Park, Indonesia.
“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,” Dr. Laumer explained.
Rakus chewed the stem and leaves of Akar Kuning, a climbing plant used in traditional medicine to treat wounds and conditions such as dysentery, diabetes, and malaria.
“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,” Dr. 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.”
Rakus repeatedly applied the resulting juice onto a wound on his right cheek for seven minutes, which he had sustained three days prior.
He then smeared the chewed leaves onto the wound until it was fully covered and continued feeding on the plant for over 30 minutes.
The researchers reported no signs of wound infection in the days following their observations. The wound had closed within five days and was fully healed within one month.
As Rakus repeatedly applied plant material to his wound but no other body parts and the entire process took over half an hour, it is likely that he intentionally treated his facial wound with Akar Kuning.
The scientists do not know whether this was the first time that Rakus treated one of his wounds or had previously learnt this behavior from other orangutans from his birth area.
As it appears that Rakus did intentionally treat his wound, this suggests that the behavior could have arisen in a common ancestor shared by humans and great apes.
“The treatment of human wounds was most likely first mentioned in a medical manuscript that dates back to 2200 BCE, which included cleaning, plastering, and bandaging of wounds with certain wound care substances,” said Dr. Caroline Schuppl, a researcher at the Max Planck Institute of Animal Behavior.
“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.”
The team’s paper was published in the journal Scientific Reports.
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I.B. Laumer et al. 2024. Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan. Sci Rep 14, 8932; doi: 10.1038/s41598-024-58988-7
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