Deep in Uganda’s Budongo Forest, researchers were amazed when they saw a chimpanzee chew a leafy plant, then gently press the pulp into the open wound of a genetically unrelated companion.
While scientists have previously observed chimpanzees treating their own injuries, this study adds compelling evidence that they also treat others, even those they aren’t related to. The findings, published in Frontiers in Ecology and Evolution, suggest that medicinal wound care may be more widespread and socially complex in chimpanzees than previously understood.
“Our research helps illuminate the evolutionary roots of human medicine and healthcare systems,” says lead author Dr Elodie Freymann from the University of Oxford. “By documenting how chimpanzees identify and utilise medicinal plants and provide care to others, we gain insight into the cognitive and social foundations of human healthcare behaviours.”
Freymann and her colleagues observed two chimpanzee communities—Sonso and Waibira—over four months. They drew on video evidence, logbooks containing decades of observational data, and a survey of other scientists who had witnessed chimpanzees treating illness or injury over the last 30 years.
“Chimpanzee wound care encompasses several techniques: direct wound licking, which removes debris and potentially applies antimicrobial compounds in saliva; finger licking followed by wound pressing; leaf-dabbing; and chewing plant materials and applying them directly to wounds,” says Freymann. “All chimpanzees mentioned in our tables showed recovery from wounds, though of course we don’t know what the outcome would have been had they not done anything about their injuries”.
Across this dataset, there are 41 documented cases of healthcare behaviour, 34 instances of self-treatment and seven of “prosocial” care, where one chimp helped another.
Among the seven cases of prosocial care, four involved wound treatment, two involved assistance with snare removal (from human set traps), and one chimp helped another with hygiene. In four of these cases, the chimps weren’t genetically related.
Freymann’s research in the Ugandan jungle (Credit: Harmonie Klein)
“These behaviours add to the evidence from other sites that chimpanzees appear to recognise need or suffering in others and take deliberate action to alleviate it, even when there’s no direct genetic advantage,” says Freymann.
The authors write that their findings: “…deepen our understanding of primate behaviour and cognition while providing additional evidence for empathic capacities in our closest evolutionary relatives.”
Given that their habitats are becoming “increasingly disrupted” and “primate populations inch closer to extinction”, the authors note that understanding the socio-ecological pressures on chimpanzee healthcare behaviours could play a vital role in informing conservation strategies.
Chimpanzees self-medicating
