Bornean orangutans do not just eat fruits and leaves. After twenty years of observations, researchers have discovered that they also consume plants with medicinal properties, even though these are not part of their usual diet.
This behavior suggests a form of self-medication among these great apes: scientists describe it as a voluntary selection, clearly distinct from accidental ingestion. This ability could change our view of animal intelligence.
Illustration image Pixabay
The team led by Georgia Allen from the University of Exeter analyzed field data collected in a swamp forest in Borneo. The orangutans there consume plants such as tree bark and specific leaves, whose extracts are known for their antimicrobial, anti-inflammatory, or wound-healing effects. Notably, these plants make up only a small part of their regular diet. Scientists see this as evidence of a targeted search for therapeutic benefits.
The researchers noted plant associations that occur much more often than chance would dictate. For example, certain plants are systematically consumed together, forming combinations with enhanced effects. This resembles a form of animal pharmacopoeia, where orangutans would select specific mixtures to treat different ailments. This observation goes beyond mere coincidence and indicates intention. The apes seem to know the properties of the plants they ingest.
How do orangutans acquire this knowledge? Georgia Allen puts forward two hypotheses: innate instinct or social learning. Juveniles might observe adults and mimic their choices. The two mechanisms are not mutually exclusive and could combine. In any case, this ability shows a form of adaptive intelligence in these great apes.
Chimpanzees are already known to consume species that reduce their internal parasites. Similar behaviors have been observed in bonobos, gibbons, and gorillas. This practice thus appears widespread among great apes, indicating deep evolutionary roots. Animal self-medication would therefore be a shared ancestral heritage.
The study also establishes a link with the knowledge of local communities. Several plants consumed by orangutans are also used by the indigenous peoples of Borneo for their medicinal properties.
By analyzing the plants that orangutans select, scientists hope to identify new natural compounds with medical applications. Tropical forests harbor a largely unexplored chemical biodiversity.