An orangutan in Sumatra surprised scientists when he was seen treating an open wound on his cheek with a poultice made from a medicinal plant. It’s the first scientific record of a wild animal healing a wound using a plant with known medicinal properties. The findings were published this week in Scientific Reports1.
“It 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,” says Caroline Schuppli, a primatologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany, and a co-author of the study.
In 2009, Schuppli’s team was observing Sumatran orangutans (Pongo abelii) in the Gunung Leuser National Park in South Aceh, Indonesia, when a young male moved into the forest. He did not have a mature male’s big cheek pads, called flanges, and was probably around 20 years old, Schuppli says. He was named Rakus, or ‘greedy’ in Indonesian, after he ate all the flowers off a gardenia bush in one sitting.
In 2021, Rakus underwent a growth spurt and became a mature flanged male. The researchers observed Rakus fighting with other flanged males to establish dominance and, in June 2022, a field assistant noted an open wound on his face, possibly made by the canines of another male, Schuppli says.
Rakus with his wound, two days before he was observed applying a poultice of medicinal leaves.Credit: Armas
Days later, Rakus was observed eating the stems and leaves of the creeper akar kuning (Fibraurea tinctoria), which local people use to treat diabetes, dysentery and malaria, among other conditions. Orangutans in the area rarely eat this plant.
In addition to eating the leaves, Rakus chewed them without swallowing and used his fingers to smear the juice on his facial wound over seven minutes. Some flies settled on the wound, whereupon Rakus spread a poultice of leaf-mash on the wound. He ate the plant again the next day. Eight days after his injury, his wound was fully closed.
The research group has seen no other orangutans in the national park self-medicate using akar kuning in 21 years of observation. This could be because wild orangutans in the region are rarely injured. Or perhaps Rakus is the only one who knows of this treatment, which could be a behaviour he picked up before he moved into the area.
“It is the first study to scientifically demonstrate that an animal is using a plant with medicinal properties applicable to wounds, and putting those on the wounds and consistently treating over a period of time,” says Michael Huffman, who studies animal self-medication at the Institute for Tropical Medicine at Nagasaki University in Japan.
Huffman says self-medication is seen in many species. Canadian snow geese (Anser caerulescens) swallow leaves whole to expel tape worms2. Dusky-footed wood rats (Neotoma fuscipes) line their nests with aromatic plants to fumigate parasites3. And chimpanzees (Pan troglodytes) in Gabon have been observed rubbing insects near their wounds2, potentially as treatment.
Humans might even have discovered some remedies by watching animals, he says. “Probably our ancestors were looking at other animals and learning about medicines.” When social animals communicate, “that information sticks and can last over generations”.