In the forests of Uganda, wild chimpanzees have been caught on camera doing something startlingly human: treating each other’s wounds with leaves and chewed-up plants.
In a behavior that hints at empathy and altruism, chimps demonstrated several techniques for wound care.
The scientists studied two communities of chimpanzees in the Budongo Forest, Uganda: Sonso and Waibira. These chimps (like pretty much all chimps in the wild) are vulnerable to injuries from fights, accidents, or snares set by humans. In the Sonso chimps, for instance, around 40% of all individuals have been seen with snare injuries.
Elodie Freymann of the University of Oxford and colleagues have studied these chimps for a few years. They previously found that chimps use medicinal plants to treat ailments, and in the new study, they investigated whether they treat others or just themselves. Freymann didn’t set out to find chimpanzees acting as paramedics. She had been studying what these apes ate — looking for signs they used plants with medicinal properties. Then she came across a series of surprising entries in the site’s decades-old logbooks.
“One day I was reading through the site’s logbook of unusual events (where researchers and field staff record unusual behaviors they have observed) and I noticed that there were quite a few cases of chimpanzees applying plant material to wounds,” Freymann tells ZME Science.
“As I kept reading, I found several cases of chimpanzees caring for the wounds and injuries of others. After I realized this was happening at Budongo, I began paying closer attention to when chimpanzees were wounded, and systematically recording cases of external care.”
She spent months observing two chimp communities in Budongo and piecing together videos field logs, and testimony from other researchers. She saw a pattern.
In total, the team recorded 41 cases of wound-related care. Most were acts of self-care — chimps licking wounds, pressing them with fingers or leaves, or applying chewed-up plants. But seven cases were more startling: a chimp treating someone else.
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Healing without borders
Chimps have several types of wound care: 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. The plant species involved, the researchers found, often had known uses in traditional medicine or contained chemical properties that could aid healing.
It’s not clear how useful these techniques are (i.e., if they help reduce infection or encourage healing), but they all have a plausible mechanism behind them. When a chimp treats someone else, it suggests a deeper capacity for empathy and even hints at the evolutionary origins of medicine.
In four cases, an individual applied wound treatment to another. In two others, chimps helped their companions escape snares. Once, a chimp helped another with basic hygiene.
“It was originally hypothesized that chimpanzees would only provide healthcare to genetically related individuals, consistent with kin selection theory,” Freymann tells ZME Science. “However, recent evidence has demonstrated that chimpanzees also extend prosocial healthcare to genetically unrelated group members, though such observations were previously limited to only a few study sites.” Prosocial refers to friendly or altruistic behaviors.
The findings from the Budongo Forest provide additional evidence of this phenomenon, suggesting that prosocial care directed at unrelated individuals may be more widespread in chimpanzee populations than previously recognized.
The implications stretch beyond the forest. If chimps share this capacity for caregiving, then it likely emerged before our species split from theirs some six million years ago. That would place the origins of medicine not with early humans — but with our last common ancestor. Our ancestors may have practiced the same type of wound care.
“Given the presence of these behaviors across multiple chimpanzee populations, it seems reasonable to conclude that basic healthcare behaviors likely existed in our shared common ancestor with great apes, representing an ancient evolutionary foundation upon which more complex human medical practices later developed.”
Are chimps capable of altruism?
Budongo’s chimpanzees aren’t alone in using nature’s pharmacy. Elephants, birds, and other primates have all been seen self-medicating — consuming plants or soils with healing properties. But prosocial treatment, especially involving wounds, is vanishingly rare in the animal kingdom.
That makes every new observation in Budongo precious. It also makes it important to study differences between groups to see if there is a cultural component to it.
The Sonso community, more accustomed to human observers than the Waibira chimps, displayed more cases of care. Freymann notes this may reflect “greater observation opportunities” rather than a true behavioral difference. The team also warns that rare behaviors are hard to study reliably and call for more long-term data. We asked Freymann if this could be interpreted as a form of altruism or empathy.
“The cases of prosocial medicinal care that we report here certainly add to the growing evidence that chimpanzees are capable of empathy and altruism. At the very least, chimpanzees are able to recognize when others are in need and apply the same forms of care they would apply to themselves to others, with no immediate personal benefit. The cases we report are especially interesting because the individuals providing care to others are often genetically unrelated to the wounded individual.”
But observing chimpanzee behavior is difficult and takes time. The relative rarity of these behaviors makes it difficult to identify patterns regarding when and how such care is provided.
The relative rarity of prosocial healthcare makes it challenging to identify patterns regarding when and why such care is provided or withheld. These limitations highlight directions for future research in this emerging field.
Freymann’s next steps include identifying which plants chimps use for wound care across different forests. Are some medicinal plants favored species-wide? Or do they rely on whatever local flora is available?
Whatever the answer, these studies are beginning to unravel an ancient type of medicinal care — not of white coats and stethoscopes, but of leafy salves, wounded limbs, and quiet acts of compassion beneath the trees.
The study was published in Frontiers in Ecology and Evolution.