The high intelligence levels of orangutans have long been recognized, in part because of their practical skills such as using tools to crack nuts and forage for insects. But new research suggests the primate has another handy skill in its repertoire: the application of medicinal herbs.
Researchers say they have seen a male Sumatran orangutan treat an open facial wound with juice and chewed leaves of a plant known to have anti-inflammatory and pain-relieving properties.
This is not the first time that wild animals have been seen self-medicating: among others, Bornean orangutans have been seen rubbing their arms and legs with chewed leaves of a plant used by humans to treat sore muscles, while chimpanzees have been recorded which chew plants known to treat worm infections and apply insects to wounds.
However, the new discovery is the first time a wild animal has been observed treating open wounds with a substance known to have medicinal properties.
“In the chimpanzee case they used insects and unfortunately it was never found out whether these insects really promote wound healing. Whereas in our case the orangutan used the plant, and this plant has known medical properties,” says Dr Caroline Schuppli, senior author of the research based at Max Planck Institute of Animal Behavior in Germany.
The team say the findings provide insight into the origins of human wound care – the treatment of which was first mentioned in a medical manuscript dating back to 2200 BC.
“It certainly shows that these basic cognitive abilities that you need to come up with a behavior like this … were most likely present at the time of our last common ancestor,” Schuppli said. “So that it goes back very, very far.”
Write in the journal Scientific ReportsSchuppli and colleagues report how they made the discovery while working in a research area of a protected rainforest in Indonesia.
The team describes how, while tracking down a male Sumatran orangutan named Rakus, they noticed that he had a fresh facial wound – likely the result of a fling with another male. Three days later, Rakus was seen feeding on the stem and leaves Fibraurea tinctoria – a type of liana climbing vine.
Then he did something unexpected.
“Thirteen minutes after Rakus began feeding on the liana, he began chewing the leaves without swallowing them and using his fingers to apply the plant juice from his mouth directly to his facial wound,” the researchers write.
Rakus not only repeated the actions, but soon after he smeared the entire wound with the chewed leaves until it was completely covered. Five days later, the facial wound was closed, while it healed within a few weeks, leaving only a small scar.
The team says the plant used by Rakus is known to contain substances with, among other things, antibacterial, anti-inflammatory, anti-fungal, antioxidant, analgesic and anticarcinogenic properties, while this and related liana species are used in traditional medicine “to to treat various diseases, such as dysentery, diabetes and malaria”.
It remains unclear whether Rakus figured out the process himself or learned it from another orangutan, although it has not been seen in any other individual.
Schuppli added that Rakus appears to have used the plant on purpose.
“It shows that to some extent he has the cognitive abilities he needs to treat the wound with some medicinally active plants,” she said. “But we really don’t know how much he understands.”
