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A Sumatran orangutan has become the first wild animal seen self-medicating with a plant to heal a wound. The male orangutan, named Rakus, had sustained a wound on his cheek pad, most likely from fighting other males, researchers said in a study published in the journal Scientific Reports. Rakus was seen chewing liana leaves without swallowing them, then using his fingers to apply the resulting juice onto the wound, the researchers said. Finally, he covered the wound up completely with a paste he had made by chewing the leaves and continued feeding on the plant. Five days after he was seen applying the leaf paste onto the wound it was closed, and a month later barely visible. Rakus is seen with a facial wound below his eye. Two months later the wound was almost invisible. It is the first documented case of active wound treatment by a wild animal with a plant known to have medicinal qualities. The leaves were from a liana known as akar kuning (Fibraurea tinctoria in Latin), which is used in traditional medicine to relieve pain, reduce fever and treat various diseases, such as diabetes and malaria. It also has antibacterial, anti-inflammatory, antifungal and antioxidant properties. "To the best of our knowledge, there is only one report of active wound treatment in non-human animals, namely in chimpanzees," the researchers wrote. "This possibly innovative behaviour presents the first systematically documented case of active wound treatment with a plant species known to contain biologically active substances by a wild animal and provides new insights into the origins of human wound care." The orangutan's behaviour was recorded in 2022 by Ulil Azhari, a co-author and field researcher at the Suaq Project in Medan, Indonesia. Scientists have been observing orangutans in Indonesia's Gunung Leuser National Park since 1994, but they hadn't previously seen this behaviour. It's possible Rakus learned the technique from other orangutans living outside the park and away from scientists' daily scrutiny, said co-author Caroline Schuppli at Max Planck. Rakus was born and lived as a juvenile outside the study area. Researchers believe the orangutan got hurt in a fight with another animal. It's not known whether Rakus earlier treated other injuries. ABC/wires