It was summer 2022 in the Sumatran rainforest when an orangutan named Rakus began applying the juice of a plant to a wound on his face. In the following days, the wound didn’t become infected. It only left a faint scar.
Rakus’ use of plants on his injury might reveal new information about how we care for our wounds today, said scientists in a study published this week.
“This possibly innovative behavior presents the first systematically documented case of active wound treatment with a plant species know to contain biologically active substances by a wild animal and provides new insights into the origins of human wound care,” said researchers in the study published Thursday in the Nature journal.
Rakus – a flanged male with cheek pads – was first observed with a fresh wound on his flange and inside his mouth on June 22, 2022. Rakus likely received the injury in a fight with another flanged male. While at the Suaq Balimbing research area of Gunung Leuser National Park in South Aceh, Indonesia, the orangutan started feeding on the stem and leaves of liana (vine) of Fibraurea tinctoria plant.
“Found in tropical forests of Southeast Asia, this and related liana species are known for their analgesic, antipyretic, and diuretic effects and are used in traditional medicine to treat various diseases, such as dysentery, diabetes, and malaria,” said the researchers. “Previous 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.”
Although the Fibraurea tinctoria plant is part of the orangutans’ diet in this area, the liana is rarely eaten.
Around 13 minutes after Rakus began eating the liana, he started chewing the leaves without swallowing them. He then used his fingers to apply the plant juice from his mouth on his facial wound.
“After this period… flies of an unknown species appeared on the wound,” said the study. “Rakus then smeared the entire wound with the plant pulp until the red flesh was fully covered with the green leaf material,” and continued feeding for around a half hour. He also rested more after receiving the injury, which may have helped healing.
By June 30, Rakus’ wound was closed and by July 19 it was fully healed. His behavior provides new insight into self-medication in animals.
“Although self-medication in non-human animals is often difficult to document systematically due to the difficulty of predicting its occurrence, there is widespread evidence of such behaviors as whole leaf swallowing, bitter pith chewing, and fur rubbing in African great apes, orangutans, white handed gibbons, and several other species of monkeys in Africa, Central and South America and Madagascar,” the study authors explained.
A 2020 study published in the Peer Life & Environment also said the “notion that tool-use is unique to humans has long been refuted by the growing number of observations of animals using tools across various contexts.”
Whole leaf swallowing, a behavior among primates that may have therapeutic qualities, was first described by Jane Goodall in the 1960s. Other forms of self-medication have been observed in wild great apes since then. Records of human treatment of wounds likely goes back to 2200 B.C.
Study authors said Rakus’ use of the plant material on his wound was never observed in another orangutan during 21 years and 28,000 hours of study in the Suaq research area. However, they said that injured orangutans are rarely observed there.
Outside of the research area, Bornean orangutans at Sabangau peat swamp forest in Central Kalimantan were also observed chewing leaves and applying them to their arms and legs for around 35 minutes. This behavior was observed again 10 years later.
“The behavior appeared to be intentional as only specific body parts were treated, the behavior was repeated several times until the hair was fully wet and the entire process took a considerable amount of time,” said researchers.
It is not known whether Rakus learned how to treat his would from another orangutan or if he decided to do it on his own. Researchers said both options are possible, since they do not know what area Rakus originated from and since the plant he used has analgesic properties that may have immediately brought pain relief.