A wild male Sumatran orangutan has been observed applying the chewed leaves of a plant with known medicinal properties to a wound on his cheek.
It is believed to be the first systematically documented case of active wound treatment with a known biologically active plant substance by a wild animal.
The researchers observed the orangutan, which they named Rakus, in June 2022 in the Suaq Balimbing research area in Gunung Leuser National Park, Indonesia.
Exactly how he got the facial injury on his right cheek pad, or flange, is unknown. However, according to the authors, flanged males typically acquire these kinds of wounds during fights with other flanged males.
“Three days after the injury he selectively ripped of leaves of a liana [plant] with the common name Akar Kuning (Fibraurea tinctoria), chewed on them, and then repeatedly applied the resulting juice onto the facial wound,” the authors write.
“As a last step, he fully covered the wound with the chewed leaves.”
Rakus then continued feeding on the plant for more than 30 minutes.
Fibraurea tinctoria is used in traditional human medicine to treat wounds and conditions such as dysentery, diabetes, and malaria.
The paper is published in the journal Scientific Reports.
Prior to this, multiple wild primate species have been observed self-medicating by swallowing, chewing, or rubbing plants with medicinal properties. But this is the first report to describe an animal applying them to recent wounds.
“Found in tropical forests of Southeast Asia, [Fibraurea tinctoria] and related liana species are known for their analgesic, antipyretic, and diuretic effects,” the authors write.
“Previous analyses of plant chemical compounds show the presence of furanoditerpenoids and protoberberine alkaloids, which are known to have antibacterial, anti-infammatory, anti-fungal, antioxidant, and other biological activities of relevance to wound healing.”
The herbal ointment may have reduced pain and inflammation and supported wound healing.
The authors reported no signs of infection in the days following their observations. The wound had closed within 5 days and was fully healed within 1 month.
The authors say the study provides new insights into the existence of self-medication in our closest relatives and in the evolutionary origins of wound medication more broadly.
“As forms of active wound treatment are not just a human universal 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 behaviour,” they write.
