Orangutan is seen healing himself with a plant poultice for the first time

by Valentina Moya (20 May 2024)

A group of scientists in Indonesia witnessed an orangutan healing himself by spreading chewed-up leaves over a facial injury, similar to a human using an ointment. This is the first time researchers have observed a wild animal treat a wound with a plant scientifically known to have medicinal properties, raising new questions in evolutionary history. 

The team, which has followed orangutans across the Gunung Leuser National Park for decades, first noticed the male orangutan’s wound in late June 2022. Three days later, they evidenced how Rokus, the orangutan, adopted a self-medicating behaviour: he fed on a climbing liana plant they rarely eat and then proceeded to coat the injury using his fingers to smear the poultice made of chewed-up leaves, doing this for several minutes. 

Rakus repeated this ritual the next day. A week later, the wound had already closed, and less than a month later it had healed with no signs of infection.

The plant, known as akar kuning, or yellow root, is used by people across Southeast Asia and China to treat diabetes, malaria, and other conditions. It is known to have anti-inflammatory, anti-fungal, antioxidant, pain-killing, and antibacterial properties. 

This is not the first time that an animal has been seen to use plants to self-medicate. It is known, for example, that other primates like chimpanzees, bonobos, and gorillas ingest and chew other plants to treat worm infections or to expel parasites.

Other species, such as Canadian snow geese, dusky-footed wood rats, and Indian civets have also adopted similar behaviours. Previous research has also recorded chimpanzees using insects to treat wounds.  

However, it is the first time a wild animal has been observed treating open wounds with a substance known to have medicinal properties. “It is the first study to scientifically demonstrate that an animal uses a plant with medicinal properties applicable to wounds, and using it on the wounds consistently over a period of time,” said Michael Huffman from the Institute for Tropical Medicine at Nagasaki University to Nature Magazine. 

Researchers are still trying to understand how Rokus figured this out: whether he learned it himself or saw another species adopt this behaviour. 

Caroline Schuppli, a primatologist at the Max Planck Institute of Animal Behavior and a co-author of the study, stated to The Guardian that this self-medicating behaviour “shows that he, to some extent, has the cognitive capacities that he needs to treat the wound with some medically active plants”. She also added that they “really don’t know how much he understands.” 

Schuppli also stated that this finding “shows that orangutans and humans share knowledge. Since they live in the same habitat, I would say that’s quite obvious, but still intriguing to realize”. Some scientists say Rakus’ behaviour could also come from common ancestors that humans share with great apes. 

Image copyright: © Armas Fitra & TNGL & KLHK & MPI & UNAS & YEL