In June 2022, a wild male Sumatran orangutan named Rakus chewed the leaves of a tropical vine, then deliberately smeared the resulting pulp onto a fresh wound on his face. Researchers who had been monitoring him in Indonesia’s Gunung Leuser National Park documented what appears to be the first known case of a wild animal actively treating an open wound with a plant that has well-established medicinal properties. The wound never became infected and was fully closed within five days, healed to a faint scar within a month. The observation has reshaped conversations about animal intelligence, the origins of medicine, and what the rainforest pharmacy still has to teach us.
What Rakus Actually Did
Rakus, an adult flanged male estimated to be in his thirties, had sustained a wound on his face, likely during a conflict with another male. Three days later, on June 25, 2022, field observers watched him begin feeding on the stem and leaves of a liana called Fibraurea tinctoria, known locally as Akar Kuning. The plant is part of the orangutan diet at this site, but it is eaten only rarely, turning up in about 0.3% of all recorded feeding observations across roughly 390,000 scans.1Scientific Reports. Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan
Thirteen minutes after he started feeding on the vine, Rakus shifted his behavior in a way that caught the researchers’ attention. He chewed the leaves without swallowing them, then used his fingers to apply the resulting juice directly onto the open wound on his face. He repeated this several times over about seven minutes. When flies began landing on the wound, he went further: he smeared the chewed plant pulp across the entire wound surface until the exposed flesh was completely covered by the green leaf material. He then continued feeding on the plant for a total of about 34 minutes.1Scientific Reports. Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan
What made the event remarkable was not just the application of plant material to a wound, which other animals occasionally do in indirect ways, but the specificity and apparent intentionality. Rakus selected a plant that happens to have strong bioactive properties. He processed it in his mouth before applying it. He covered the wound thoroughly. And he did all of this in a sustained, methodical sequence rather than an accidental smear.
Why Akar Kuning Is Not Just Any Plant
Fibraurea tinctoria is well known in traditional medicine across Southeast Asia. Local communities use it for a range of ailments, and laboratory research has confirmed that the plant is loaded with biologically active compounds. An analysis of its chemical composition found that its extracts are rich in tannins, alkaloids, saponins, and phenolic compounds. An ethanol extract of F. tinctoria contained roughly 57% tannins and over 4% saponins, while a water-based extract showed about 37% tannins and over 15% phenolic compounds.2IOP Conference Series: Earth and Environmental Science. Potency of Fibraurea tinctoria Lour. extract as anti-bacterial agents towards pathogenic bacteria These are not trace amounts. The plant is a concentrated source of exactly the kinds of chemicals that fight infection and reduce inflammation.
Tannins are astringent compounds that can promote blood clotting and form a protective barrier on tissue. Phenols are broad-spectrum antimicrobials. Saponins have both antimicrobial and anti-inflammatory effects. And the alkaloid content matters too. Across the plant kingdom, alkaloids have been shown to suppress inflammatory signaling pathways, reducing the production of molecules that drive swelling and tissue damage.3PubMed Central. Molecular Mechanisms of Wound Healing: The Role of Medicinal Plants Separately, at least one alkaloid (taspine, from a different plant) has been shown to promote the early phases of wound healing by attracting fibroblasts, the cells that lay down new tissue.4PubMed. Enhancement of wound healing by the alkaloid taspine defining mechanism of action
None of this proves that Rakus “knew” the biochemistry. But it does mean he chose, out of everything in the forest, a plant whose chemical profile would be a sensible wound treatment. This was not a nutritionally valuable food he happened to rub on his face. Akar Kuning makes up a tiny fraction of the orangutan diet at this site. Rakus went out of his way to use it, and he used it in a way that maximized contact between the plant’s juice and his injured tissue.
The Wound Healed Remarkably Well
Researchers continued monitoring Rakus in the days after the treatment. Photographs taken on June 26 and 28 showed no visible signs of infection. By June 30, just five days after the plant application, the wound had closed. By July 19, roughly three and a half weeks later, the wound appeared fully healed, with only a faint scar remaining.5Scientific Reports. Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan – Section: Results
Open facial wounds in wild animals are vulnerable to infection, especially in tropical environments where insect pressure is constant and microbial loads are high. The fact that Rakus’s wound healed cleanly and quickly is consistent with the antimicrobial and anti-inflammatory properties of the plant, though this is a single case and researchers are careful not to claim a proven causal relationship. There was no control group of orangutans with similar wounds who did not use the plant. Still, the outcome aligns neatly with what the chemistry would predict.
Self-Medication in Other Primates
Rakus’s behavior would be less striking if it existed in a vacuum, but it fits into a growing body of evidence that great apes and other primates routinely use plants in ways that go beyond nutrition. Chimpanzees, for instance, have been documented swallowing the rough, bristly leaves of certain plants whole, without chewing them. Researchers in Uganda found a clear relationship between this leaf-swallowing behavior and the expulsion of intestinal parasites, including nematode worms and tapeworms.6PubMed. High frequency of leaf swallowing and its relationship to intestinal parasite expulsion in “village” chimpanzees at Bulindi, Uganda The physical texture of the unchewed leaves appears to dislodge worms from the intestinal wall.
A longer-term study in Kibale National Park tracked leaf-swallowing in two chimpanzee communities over six and a half years. During a seven-month period when tapeworm fragments appeared in fecal samples, leaf-swallowing spiked to an unusually high rate. Dung that contained tapeworm fragments tended to also contain whole swallowed leaves, suggesting that the chimpanzees ramp up the behavior specifically when dealing with an active parasitic infection.7PubMed. Relationship of chimpanzee leaf-swallowing to a tapeworm infection
But these chimpanzee examples involve ingestion for internal parasites. The Rakus case is different because it involves topical application for an external wound. That distinction matters. Swallowing a leaf requires relatively little innovation beyond recognizing which plants help with a stomachache. Chewing plant material, extracting its juice, and applying it by hand to a specific injury site on your own body requires a more complex chain of actions. The topical treatment is more reminiscent of what a human herbalist might do than what a sick animal might stumble into.
Orangutans in Borneo Use Plants Too, But Differently
Rakus is a Sumatran orangutan, but his Bornean cousins have their own medicinal traditions. In the Sabangau peat-swamp forest in Borneo, orangutans have been observed rubbing chewed leaves of Dracaena cantleyi into their fur, concentrating on their arms. Chemical analysis of the plant revealed anti-inflammatory properties, and the researchers concluded that the fur-rubbing likely serves as a form of self-treatment for sore muscles and joints.8Scientific Reports. Self-medication by orang-utans (Pongo pygmaeus) using bioactive properties of Dracaena cantleyi Local indigenous people in Borneo use the same plant for the same purpose: to treat muscular pain, sore bones, and swelling.
That overlap between orangutan and human use of the same plant is striking. The researchers noted that primarily adult females performed the Dracaena fur-rubbing behavior (nine out of ten observed cases), possibly because the extra weight of carrying offspring through the canopy puts particular strain on their arms. The behavior appears socially transmitted within the population, not something every orangutan discovers independently.
A more recent study investigating the broader dietary patterns of Bornean orangutans noted that Fibraurea tinctoria, the same plant Rakus used on his wound in Sumatra, also appears in the Bornean orangutan diet. The authors highlighted the pharmacological relevance of this species and its potential functional importance in orangutan health behaviors beyond simple nutrition.9Scientific Reports. Investigating medicinal resource combinations in the Bornean orangutan diet In other words, different orangutan populations on different islands seem to have independently incorporated medically useful plants into their behavioral repertoires, sometimes for different purposes.
How Do Animals Figure This Out
The instinctive question when watching Rakus smear plant pulp on his wound is: did he know what he was doing? The honest answer is that we do not know, and the question itself may be framed too narrowly. Research on animal self-medication across a wide range of species suggests that high-level cognitive sophistication is not always necessary. A broad review of animal medical behaviors concluded that advanced cognition is not necessarily a prerequisite, because innate mechanisms likely play a role in many of these behaviors across the animal kingdom.10PubMed Central. Animal medical systems from Apis to apes: history, recent advances and future perspectives
Insects, for instance, self-medicate without anything resembling primate cognition. Monarch butterflies preferentially lay eggs on milkweed species that contain antiparasitic compounds when they are infected with parasites. Honeybees incorporate antimicrobial resins into their hives. These behaviors are largely hardwired. In primates, the picture is more complex. A review in Current Biology laid out three routes through which animal medication can arise: innate ability, social learning, and individual associative learning. These routes are not mutually exclusive; a single behavior could involve elements of all three.11Current Biology. Animal medication
For Rakus specifically, researchers have raised the possibility that the behavior was learned by observing other orangutans treat their own wounds, though no one has documented another orangutan doing exactly this. It could also reflect individual trial-and-error learning: Rakus might have previously noticed that chewing Akar Kuning soothed mouth pain or irritation, and extrapolated that the same plant might help a wound. Or it could be partly innate, a disposition to apply soothing plant material to painful areas that gets refined through experience. In any case, the behavior did not look accidental. The deliberate, multi-step process of chewing, extracting, and applying suggests at minimum some kind of understanding that the plant material should go on the wound.
Identifying Medicines in Animal Diets
One challenge in studying animal self-medication is figuring out which items in a primate’s diet are food and which are pharmacy. Researchers at Budongo Forest in Uganda developed new analytical approaches to test whether chimpanzees combine dietary resources in nonrandom ways that suggest medicinal intent. Rather than waiting to catch a sick animal eating a particular plant and then testing that plant, these methods look at statistical patterns across the whole diet to flag plant combinations that seem to appear together more often than chance would predict.12PubMed. Applying collocation and APRIORI analyses to chimpanzee diets: Methods for investigating nonrandom food combinations in primate self-medication
This kind of analytical innovation matters because the traditional approach to studying zoopharmacognosy (the fancy term for animals using plants as medicine) relies on catching rare events and then working backward. You see a sick animal eat something unusual, you test that plant in a lab, and if it has bioactive properties, you tentatively call it self-medication. The problem is that you miss everything you do not witness directly. Methods that can identify candidate medicinal plants from dietary data alone could accelerate discovery considerably, revealing patterns that decades of behavioral observation might never catch.
What Animal Pharmacies Mean for Human Medicine
There is a practical, human-centered reason to care about orangutans treating their wounds. If wild animals are effectively screening the forest for bioactive compounds, researchers can piggyback on millions of years of natural selection to identify plants worth investigating. This idea, sometimes called zoopharmacology, has gained traction in drug discovery circles. A review exploring this approach found that several plants used by animals in self-medication contexts contain secondary metabolites with antitumor activity, and that in some cases humans in the same regions use those plants for similar therapeutic purposes.13PubMed Central. Zoopharmacology: A Way to Discover New Cancer Treatments
The logic is straightforward. Tropical forests contain hundreds of thousands of plant species, many of them chemically uncharacterized. Testing them all systematically for bioactivity would take centuries and enormous funding. But if a chimpanzee with a parasitic infection reliably seeks out a particular plant, or an orangutan applies a particular vine to a wound that then heals without infection, that behavior functions as a bioassay. The animal is telling you, in effect, “this plant does something useful.” Researchers can then prioritize those plants for chemical and pharmacological analysis, dramatically narrowing the search space.
The connection between great ape self-medication and the origins of human herbal medicine has also attracted attention from evolutionary biologists. One widely cited perspective argued that studying self-medication in African great apes opens a window into how early humans might have first discovered the therapeutic properties of plants.14BioScience. Self-Medicative Behavior in the African Great Apes: An Evolutionary Perspective into the Origins of Human Traditional Medicine If chimpanzees and orangutans can identify and use medicinal plants through some combination of innate predisposition, social learning, and individual experimentation, our common ancestors likely could too. Human traditional medicine may not have started from scratch. It may have built on a behavioral foundation that is tens of millions of years old.
Why a Single Orangutan’s Wound Matters
It is worth being honest about the limits of this evidence. Rakus is one orangutan, observed on one occasion, treating one wound. The researchers themselves emphasize that this is a single documented case and do not claim to have proven that orangutans routinely treat wounds this way. Without repeated observations, controlled comparisons, or documentation of the behavior in other individuals, the strongest version of the claim remains tentative.
That said, single-case observations in field primatology often turn out to be the first reports of behaviors that are later found to be widespread. Jane Goodall’s first observation of a chimpanzee using a twig to fish for termites was initially met with skepticism; tool use in chimpanzees is now one of the best-documented behaviors in primatology. The chimpanzee leaf-swallowing described above was initially a handful of scattered observations before systematic monitoring revealed it to be a common, population-wide behavior linked to specific health conditions. Rakus’s wound treatment may be the tip of a much larger behavioral iceberg, or it may turn out to be genuinely rare. Either finding would be scientifically interesting.
The observation also depends on having long-term research infrastructure in place. The team that documented Rakus’s behavior has been monitoring orangutans in this part of Sumatra for decades, with hundreds of thousands of feeding observations in their database. That kind of sustained effort is expensive and precarious. If the research station had been closed, or if the forest had been converted to palm oil plantation, no one would have been there to see what Rakus did. The discovery is as much a testament to the value of long-term field research as it is to orangutan intelligence.
Fibraurea tinctoria Beyond Wound Care
The plant Rakus used has a pharmacological profile that extends well beyond wound treatment. Laboratory studies in rats have found that an ethanol extract of Fibraurea tinctoria significantly lowered blood glucose levels in a dose-dependent manner, with the most effective dose producing results comparable to established diabetes treatments.15Research Journal of Pharmacy and Technology. Antidiabetic activity of Akar Kuning (Fibraurea tinctoria Lour) Extract in Alloxan-Induced Diabetic White Male Rats The same plant’s antibacterial properties have been confirmed directly against pathogenic bacteria in laboratory settings.2IOP Conference Series: Earth and Environmental Science. Potency of Fibraurea tinctoria Lour. extract as anti-bacterial agents towards pathogenic bacteria
Traditional human uses of Akar Kuning across Southeast Asia include treatment of infections, fever, and digestive complaints, applications that align with the plant’s confirmed antimicrobial, anti-inflammatory, and metabolic effects. The fact that an orangutan independently arrived at a topical use for this plant, without any cultural transmission from humans, adds a strange kind of convergent evidence. When two very different species with no shared pharmacological tradition both reach for the same plant, it suggests the plant’s bioactive properties are robust enough to be discovered through experience alone.
Researchers studying Bornean orangutan diets have already begun flagging F. tinctoria as a species of particular pharmacological interest, noting both its topical use by Rakus and its presence in the Bornean orangutan diet as evidence for its functional importance in orangutan health behaviors.9Scientific Reports. Investigating medicinal resource combinations in the Bornean orangutan diet The plant is now likely to receive considerably more scientific attention than it otherwise would have, a concrete example of how a single behavioral observation in a wild animal can redirect pharmaceutical research priorities.