A male Sumatran orangutan named Rakus.
Credit: Reuters Photo
Evidence of the first case of a wild animal treating their wound with medicinal plants was reported in a new study.
At the Suaq Balimbing research site in Indonesia, researchers observed that a male Sumatran orangutan repeatedly chewed and applied sap from a climber plant to a wound on his cheek.
"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 neighbouring male," said Isabelle Laumer from the Max Planck Institute of Animal Behavior (MPI-AB), Germany.
The research site is a protected rainforest area home to approximately 150 critically endangered Sumatran orangutans. The team included researchers from Universitas Nasional, Indonesia.
Three days after the injury, Rakus 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 precisely onto the facial wound for several minutes, the researchers described.
As a last step, he fully covered the wound with the chewed leaves, they said.
Laumer explained that the plant and related liana species, found in tropical forests of Southeast Asia, are known for their pain-relieving, anti-inflammatory, and other properties important to wound healing.
The plants are used in traditional medicine to treat various diseases, such as malaria, dysentery and diabetes, said Laumer, first author of the study published in the journal Scientific Reports.
The researchers observed no signs of wound infection in the days following the injury. They also saw that the wound closed within five days and fully healed within one month.
"Interestingly, Rakus also rested more than usual when being wounded. Sleep positively affects wound healing as growth hormone release, protein synthesis and cell division are increased during sleep," Laumer said.
She explained the "intentional" nature of Rakus's behaviour, as he "selectively treated his facial wound," and no other body part.
"The behaviour 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.
While multiple wild primate species have so far been observed swallowing, chewing, or rubbing plants with medicinal properties, this is the first time that they applied them to recent wounds, the researchers said.
Thus, medical wound treatment may have arisen in a common ancestor shared by humans and orangutans, they said.
"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," the authors wrote.