Long-term field data points to selective medicinal feeding
Researchers studying Bornean orangutans in Indonesian Borneo have found evidence that the apes may be using plants in ways that resemble self-medication. Drawing on 20 years of observations in a peat-swamp forest in Central Kalimantan, the team examined how often orangutans consumed plants with known medicinal properties and whether those plants appeared together in meaningful patterns.
The study, published in Scientific Reports, does not claim that orangutans diagnose illness in a human sense. But it does report something more specific than opportunistic feeding: certain plants with antimicrobial, anti-inflammatory or wound-healing properties showed up in combinations and sequences that were more frequent than chance alone would predict.
That distinction matters. Animals eat a wide range of plants for calories, fiber and micronutrients. The new work suggests some plant choices may serve an additional function. Several of the species flagged by the researchers are not major staples in the orangutan diet overall, which weakens the simpler explanation that they are being eaten only because they are common or especially nutritious.
What the researchers actually found
Georgia Allen, who led the study as part of a master’s program in conservation and biodiversity at the University of Exeter, said the team cannot yet say that orangutans are consciously treating specific conditions. The evidence instead points to selective consumption patterns that go beyond ordinary nutrition.
According to the study summary, some plant species appeared together in the orangutans’ diet far more often than expected by chance. Those plants are known to contain compounds linked to antimicrobial, anti-inflammatory or wound-healing effects. That pattern is consistent with medicinal resource use, especially when combined with the fact that the plants involved are not dominant everyday foods.
In practice, that means the researchers are not just arguing that orangutans sometimes eat useful plants. They are arguing that the apes may be combining or sequencing those plants in repeatable ways that could produce health benefits. The finding adds nuance to a growing body of animal behavior research showing that food selection can overlap with disease management.
Part of a broader animal pattern
Self-medication has already been documented or strongly suggested in several other primates. Chimpanzees, for example, are known to consume plants that can reduce internal parasite infections. Similar behaviors have also been observed in bonobos, gibbons and gorillas. The orangutan findings fit within that broader pattern while extending it with a long observation window and a focus on combinations of medicinal resources rather than single-plant use alone.
That is a meaningful step. If the same plant repeatedly appears alongside other biologically active species, researchers can begin asking whether animals are exploiting complementary effects. Even without proving intent, repeated nonrandom combinations suggest a more structured interaction with the forest pharmacopoeia than feeding studies often capture.
The study also highlights the value of long-term field observation. Behaviors tied to health may be sporadic, seasonal or linked to conditions that are hard to observe directly. Short study windows can miss those patterns entirely. A dataset spanning two decades gives researchers a better chance of distinguishing routine feeding from rarer, more targeted behavior.
Why this matters beyond orangutan behavior
The implications extend into conservation and biomedical research. Some of the plants eaten by the orangutans are also used medicinally by local Indigenous communities. That overlap does not prove the apes and people are using the plants for the same purposes, but it does strengthen the case that these forest species contain biologically active compounds with real effects.
It also underscores a recurring theme in biodiversity science: ecological knowledge is distributed across both human traditions and nonhuman behavior. Preserving habitats protects not only species, but also the web of relationships through which useful biological knowledge can be discovered and interpreted.
For conservationists, the study offers another reason to protect peat-swamp forests in Borneo. These ecosystems are already under pressure from land-use change and degradation. If they are also repositories of medicinal plants used by endangered great apes, habitat loss becomes a direct threat to a behavioral repertoire that may have taken generations to develop or transmit.
The researchers note that it remains unclear how orangutans learn this behavior. Two possibilities stand out in the study summary: instinct and social transmission across many generations. Those are not mutually exclusive. A predisposition to sample certain plants could be reinforced by observation, local ecological conditions or inherited feeding traditions within populations.
What the study does and does not prove
The strongest reading of the research is also the most careful one. The study supports the idea that orangutans selectively consume medicinal plants in nonrandom combinations and sequences. It does not establish that the animals understand disease in a human-like way, nor does it prove a direct cause-and-effect link between a given plant combination and an observed recovery from illness.
That caution is important because claims about animal medicine can easily become overstated. Still, the evidence appears strong enough to shift the discussion. Rather than asking only whether orangutans ever consume medicinal plants, scientists can now ask when they do so, in what combinations, and under what physical or environmental conditions.
Those are the kinds of questions that turn intriguing anecdotes into a deeper science of animal health behavior. If future work links particular feeding sequences to visible wounds, digestive stress, infection risk or seasonal disease pressure, the case for self-medication in orangutans will become much more specific.
For now, the new study adds weight to a compelling possibility: one of humanity’s closest relatives may be navigating its environment not just as a source of food, but as a living pharmacy. That idea is scientifically useful, conservationally relevant and a reminder that sophisticated health-related behavior does not begin and end with humans.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
