Chimpanzees use medicinal leaves to heal wounds, scientists discover

Apes help care for individuals they are not related to, study in Uganda's Budongo Forest shows

Studying chimpanzees can help humans understand 'our evolutionary origins', researchers say. Photo: Dr Elodie Freymann

Chimpanzees use medicinal plants to clean their own wounds and those of others in their community, research has found.

Scientists say the "surprising" findings, based on detailed observations of the primates in the forests of Uganda, could shed light on the social bonds that led to health care among human beings.

The first author of the study, Dr Elodie Freymann, of the Institute of Human Sciences at the University of Oxford, said chimpanzees may also care for unrelated individuals “to build future alliances that could benefit them”.

“But it is also possible that this is a form of altruism that we’re seeing – chimpanzees helping others simply for the sake of helping. I don’t think that’s out of the question,” she told The National.

In Uganda’s Budongo Forest, Dr Freymann and her colleagues spent four months observing two communities of chimpanzees, the Sonso and Waibira. The researchers also pored through logbooks containing detailed observations stretching back decades, and surveyed other scientists who saw chimpanzees helping one another.

Many of the animals suffered injuries caused by accidents, fights or snares, with about four in 10 of the Sonso chimpanzees having been hurt by snares.

Socially minded

As well as recording dozens of cases of individuals carrying out care on themselves, the scientists witnessed seven instances of chimpanzees helping others, something known as prosocial care. Four cases of prosocial care involved animals helping individuals they were not related to.

The animals licked wounds, which cleared out debris and may have promoted healing because of the antimicrobial properties of saliva. They also licked their fingers and pressed them to wounds, dabbed leaves on injuries and chewed plant materials before applying them to lesions.

Once the researchers identified which plants the animals were using on their wounds, they went through scientific literature to see how these plants were traditionally used by people and whether they contained substances that are bioactive, meaning they have effects on organisms.

Researcher Dr Elodie Freymann carries out fieldwork in the Budongo Forest of Uganda. Photo: Austen Deery

“We found that quite a few of them did, and interestingly several of these plants had uses and properties relevant to wound healing,” she said.

All chimpanzees observed closely by the scientists recovered, although the researchers said the animals may have got better even if nothing had been done to the wounds. As well as wound treatment, prosocial care also involved removing snares and helping other chimpanzees with hygiene.

Rare behaviour

Dr Freymann said that, until now, there were just “a handful” of documented cases of chimpanzees showing prosocial care towards unrelated individuals. As a result, she was “surprised” to read such accounts in the research site’s logbook of unusual behaviour.

“Chimpanzees are incredibly intelligent and social animals, so why shouldn’t they be capable of recognising that others in their community need external assistance, and then provide that care? Our study expands the list of wild chimpanzee sites where this kind of prosocial care occurs, showing that it is more widespread and less rare than we previously thought," she said.

Humans can “learn a lot about ourselves and our evolutionary origins” by observing wild chimpanzees, Dr Freymann said. The creatures are one of humanity’s closest living relatives.

“They serve as interesting evolutionary models for understanding what our shared common ancestor may have been capable of,” she added. “The fact that chimpanzees clearly possess the ability to take care of their own wounds, and the wounds of others in their community, suggests that the origins of our healthcare systems may be more ancient than we may have thought.”

Chimpanzees groom each other in Uganda. Photo: Dr Elodie Freymann

Knowledge about the behaviour of chimpanzees towards health care could also prove useful to efforts to protect the animals, the scientists said in their paper, published in Frontiers in Ecology and Evolution.

“As chimpanzee habitats become increasingly disrupted, and primate populations inch closer to extinction, understanding the socio-ecological pressures on chimpanzee healthcare behaviours could play a critical role in informing conservation strategies,” they wrote.

Protecting the plants the animals need to keep themselves healthy, and tackling the use of snares, could protect chimpanzees “from environmental and climatic disturbances that increasingly threaten their survival”.

Another great ape, the orangutan, made headlines a year ago when it was revealed that an injured male on the Indonesian island of Sumatra chewed plant leaves with medicinal properties and applied the juice to an open wound under his eye. A researcher involved in that work, Isabelle Laumer, told media at the time that it was the first known case of a wild animal treating a wound with a medicinal plant.

The scientists involved in the chimpanzee study worked from the Budongo Conservation Field Station, which Dr Freymann described as “an incredible field site” in the middle of the forest.

“All around you there are birds singing, insects chirping and chimps calling,” she said. “The trees are massive and many have giant buttresses that branch out along the forest floor. Every day, walking into the forest, you have the sense that anything could happen.”

Dr Freymann said there were “just so many unexplored areas” in the field of zoopharmacognosy, the term for animals self-medicating.

She aims to carry out fieldwork in the Peruvian Amazon, where she will look for signs of animal self-medication in her new role as a post-doctoral fellow at Brown University, in the US.