In June 2022, an adult male Sumatran orangutan known as Rakus suffered a facial injury beneath his right eye, likely from a skirmish with another male orangutan at the Suaq Balimbing research site, a protected rainforest area in Indonesia. However, what Rakus did three days later piqued the interest of researchers.
Scientists recently detailed Rakus's apparent self-treatment of his wound using a plant known for its pain-relieving and wound-healing properties. Rakus chewed the leaves of the plant to produce a liquid, which he then applied to the wound along with the chewed plant material, resembling a wound plaster. This behavior was observed by primatologist and cognitive biologist Isabelle Laumer of the Max Planck Institute of Animal Behavior in Germany, who is also the lead author of the study published in Scientific Reports.
The plant in question is an evergreen vine called Akar Kuning, scientifically known as Fibraurea tinctoria. Orangutans in the region rarely consume this plant, which is home to about 150 critically endangered Sumatran orangutans. Rakus's deliberate treatment of his wound with the plant represents the first documented case of active wound treatment with a plant species exhibiting medicinal properties by a wild animal, according to study senior author Caroline Schuppli, an evolutionary biologist at the institute.
Rakus, estimated to have been born around 1989, is a flanged male orangutan, characterized by the large cheek pads on his face, which are secondary male sexual characteristics. He is one of the dominant males in the region.
Researchers noted that Rakus's behavior appeared intentional and selective, focusing solely on treating his facial wound. The wound showed no signs of infection and healed within five days, during which Rakus repeatedly applied the plant material.
Schuppli suggested that the cognitive capacities required for this behavior may be as ancient as the last common ancestor of orangutans and humans, which lived approximately 13 million years ago. Orangutans, along with chimpanzees, bonobos, and gorillas, are one of the world's great apes, sharing approximately 97% of their DNA with humans. However, orangutans are the least closely related to humans among them.
This observation raises questions about how orangutans understand and learn to treat their wounds with plants. While the exact cognitive abilities involved are yet to be fully understood, wild orangutans are known for their problem-solving skills and the transmission of learned behaviors across generations through observational social learning.
The plant Fibraurea tinctoria is widely distributed across Southeast Asia and is used in traditional medicine to treat various conditions, including malaria. Orangutans, known as "people of the forest" in Indonesian and Malay languages, are the largest arboreal mammals, adapted to life in trees. They lead mostly solitary lives, sleeping and eating fruit in the forest canopy, and are known for their rich cultural repertoire, including tool use, which is passed down through generations in their populations.