Scientists have observed wild chimpanzees (Pan troglodytes troglodytes) consuming plants that have anti-bacterial and pain-relieving properties to heal themselves. They conducted detective work in the forests of Uganda, studying injured or sick animals and gathering evidence to construct a case. There were 13 members of the team who were botanists, ecologists, ethnopharmacologists, parasitologists and primatologists.
When an injured animal fetched something specific from the forest and ate it, researchers collected samples of the plant and analyzed them. A majority of plants tested turned out to have anti-bacterial properties. The scientists’ findings appeared in the journal PLOS ONE on June 20, 2024. Dr. Elodie Freymann of Oxford University’s School of Anthropology & Museum Ethnography led the study. She described the results as “thrilling.”
It has been surmised that this study could help in the search for new medicines. Antibiotic-resistant bacteria and chronic inflammatory diseases are both becoming urgent health challenges worldwide. Dr. Freymann pronounced that because humans and chimpanzees have so much in common genetically, “they are the perfect model for discovering new pharmaceuticals that could be effective for us as well.”
Dr. Freymann added, “so why not test the plants that we have this information about – plants the chimps are seeking out?” Chimps survive in the forest every day, so, she remarked, we could “use them as our teachers” to direct us to plants that could be effective medicines for us as well. Chimpanzees’ sophisticated understanding of their environment’s medicinal resources might lead us to reconsider their intelligence.
Over the last four years, Dr. Freymann has spent months-long periods carefully observing two communities of wild chimpanzees in Uganda’s Budongo Forest Central Reserve. This latest study lasted eight months. The chimps were 51 in number and accustomed to people. She and her colleagues looked for signs of pain, for instance, an animal limping or holding its body in a strange fashion. They also studied droppings and urine to check for signs of illness.
The scientists were particularly interested when an injured or ill chimpanzee ate something that wasn’t part of its usual diet or was nutritionally poor. Fruit skin or tree bark are prime examples. Dr. Freymann explained, “We were looking for these behavioral clues that the plants might be medicinal.”
One particular male chimp had a badly injured hand. While the rest of this chimp’s group sat around and ate, this one went looking for ferns. He was the only chimp to do so. Researchers took samples of this fern, Christella parasitica, and found it was potently anti-inflammatory.
Another chimp, this time with a bacterial infection, ate bark from the cat-thorn tree (Scutia myrtina). Chimps from this group had never previously been seen eating this. Testing showed that this bark was both anti-inflammatory and anti-bacterial.
One more chimp had diarrhoea and tapeworms, which was far from unusual for wild chimps in the area. Shortly after it began suffering, the chimp went with two others away from their community’s home to a place in the forest that featured a particular type of tree, Alstonia boonei. It chewed the tree’s dead wood, which has long been used in traditional medicine. Testing found that it was powerfully anti-bacterial and anti-inflammatory. The chimp staged a full recovery.
The bark and resin of the tree Khaya anthotheca were frequently used by chimps. Samples showed it to be remarkably effective against several strains of bacteria. This included some that are resistant to a number of drugs.
The strongest anti-bacterial properties were in dead wood from Alstonia boonei, a tree in the dogbane family. It was also anti-inflammatory. Interestingly, this plant has been employed by East African communities to treat a selection of conditions that include asthma, bacterial infection, gastrointestinal issues, and snakebites.
In all, the researchers took 17 samples of 13 different plant species and sent them for testing by Dr. Fabien Schultz of Germany’s Neubrandenburg University of Applied Sciences. This revealed that nearly 90% of the samples restricted bacterial growth, while a third were anti-inflammatory, reducing pain and promoting healing. Past studies have shown some of these plants to fight cancer or pain. Eleven of the 13 plant species were used in traditional medicine. Much traditional medicine in less developed countries probably came from medicine men watching animals, which is known to happen.
Dr. Freymann commented happily that all the injured and ill chimps studied fully recovered. The one who ate ferns “was using his hand again within the next few days.” It was “highly unlikely” that the chimps were eating these plants coincidentally: often, chimps sought out these plants when no other group members did. The exercise highlighted the medicinal knowledge that can be acquired from observing wild animals. It also brought attention to the urgent need to keep these “forest pharmacies” for the generations to come, or chimps would be vulnerable to conditions they were previously resistant to.
By email, Dr. Freymann attested that this study’s findings should come as no surprise because chimps “are incredibly smart and it makes perfect sense they would have figured out by now which plants can help them when ill or injured.”
The study of animals using plants or insects to self-medicate is zoopharmacognosy. In May 2024, an orangutan in Indonesia named Rakus applied the juice and chewed-up leaves of a certain plant, akar kuning (Fibraurea tinctoria), to a facial injury, leading to its healing. Two years ago, in another study of chimpanzees, this time in Gabon’s Loango National Park, scientists noted one animal repeatedly applying insects to the wounds of another, which initially left them befuddled; other chimps came to watch, which is how they learn behaviour. Taking advantage of the medicinal properties of plants isn’t confined to apes. It has also been witnessed in bears, deer, elk, elephants, lemurs and lizards. The humblest creature to do so is the fruit fly, which lays eggs in plants with high ethanol levels when there are parasitoid wasps around, which protects their offspring.
