Deep in the forests of Uganda, a team of scientific detectives has uncovered a secret: chimpanzees are running their own pharmacy.
Scientists observing wild chimpanzees (Pan troglodytes troglodytes) have confirmed that the animals deliberately seek out plants with anti-bacterial and pain-relieving properties to heal themselves.
The 13-strong team, comprising botanists and primatologists, conducted their “detective work” by trailing sick or injured animals through the Budungo Forest Central Reserve. When a chimp fetched a specific plant to eat, the researchers collected samples for analysis.
The findings, published in the journal Plos One were described as “thrilling” by lead author Dr Elodie Freymann of Oxford University.
The search for new drugs
With antibiotic-resistant bacteria and chronic inflammatory diseases becoming urgent global health challenges, the study offers a new avenue for drug discovery.
Because humans and chimpanzees share so much genetic DNA, Dr Freymann argues that “they are the perfect model for discovering new pharmaceuticals that could be effective for us as well”.
She added: “So why not test the plants that we have this information about — plants the chimps are seeking out?” By using the animals as “our teachers”, scientists hope to unlock the secrets of the forest floor.
The patients
Over eight months, Dr Freymann observed 51 chimps, looking for signs of pain — such as limping — or analysing droppings for illness. The team paid close attention when a chimp ate something nutritionally poor, such as tree bark or fruit skin.
“We were looking for these behavioural clues that the plants might be medicinal”, Dr Freymann explained.
The investigation yielded remarkable case studies:
- The injured hand: While his group ate, a male chimp with a badly injured hand went looking for ferns. He was the only one to do so. Samples of the fern, Christella parasitica, proved to be potently anti-inflammatory. The chimp was “using his hand again within the next few days”.
- The infection: A chimp with a bacterial infection ate bark from the cat-thorn tree (Scutia myrtina). Testing showed the bark was both anti-inflammatory and anti-bacterial.
- The parasite: A chimp suffering from diarrhoea and tapeworms left its community to find a specific tree, Alstonia boonei. It chewed the dead wood, a substance long used in traditional medicine. It was powerfully anti-bacterial, and the chimp staged a full recovery.
Nature’s laboratory
In total, the researchers sent 17 samples from 13 plant species to Dr Fabien Schultz at Neubrandenburg University of Applied Sciences in Germany.
The results were striking: nearly 90% of the samples restricted bacterial growth, and a third were anti-inflammatory. Interestingly, 11 of the 13 species are already used in traditional human medicine — suggesting that medicine men may have learned their craft by watching animals.
The strongest anti-bacterial properties were found in the dead wood of Alstonia boonei, a tree in the dogbane family. East African communities have historically used this plant to treat asthma, snakebites and gastrointestinal issues.
Zoopharmacognosy
The study of animals self-medicating is known as zoopharmacognosy, and the practice is surprisingly widespread.
In May 2024, an orangutan in Indonesia named Rakus applied the juice and chewed-up leaves of the Akar Kuning plant to a facial wound, which healed shortly after. Two years ago, scientists in Gabon were befuddled when they observed chimpanzees applying insects to each other’s wounds.
It is not just apes, either. Bears, deer, elephants and even lizards have been witnessed taking advantage of nature’s medicine cabinet. Perhaps the humblest pharmacist is the fruit fly, which protects its offspring from parasitoid wasps by laying eggs in plants with high ethanol levels.
For Dr Freymann, the results should come as no surprise. As she noted by email, 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”.
