When they are unwell, chimpanzees sometimes seek out and eat plants that have medicinal properties, a study published in PLOS ONE reveals.
Wild chimpanzees eat a variety of parts from a variety of plants, including the leaves, fruit, wood and pith of figs and other species. Much of their food is nutrient dense, but some is nutrient poor, prompting speculation that some plants are eaten, not for their nutritional content, but for their medicinal value.
To find out if this is the case, Elodie Freymann from Oxford University and colleagues spent eight months monitoring the health and behaviour of 51 chimpanzees, from two neighbouring communities, living in Uganda’s Budongo Forest.
During this time, she witnessed many injured and sick chimpanzees appear to self-medicate with certain plants. This included a male with an injured hand who ate leaves from a particular fern (Christella parasitica), an individual with a parasitic infection who consumed bark from the cat-thorn tree (Scutia myrtina), and an adult female with severe diarrhoea who ate bark and resin from the East African mahogany tree (Khaya anthotheca).
Freymann then collected samples from as many of these plants as she could – 17 samples from 13 species – and performed tests to assess their medicinal value.
88% of the plant extracts were found to have anti-bacterial properties. Dead wood from a tree in the Dogbane family (Alstonia boonei) had the strongest antibacterial activity and also had anti-inflammatory properties, suggesting that it could be used to treat wounds.
Meanwhile, 33% of the plant extracts had anti-inflammatory properties, including bark and resin from the East African mahogany tree and leaves from the C. parasitica fern.
Taken altogether, these results suggest that ill chimps deliberately seek out specific plants for their medicinal effects. This requires “basic awareness of the resource’s healing properties,” the authors say.
Before this study, researchers knew of two well-established types of self-medication. Chimps have been observed chewing the pith of a daisy-like shrub called Vernonia amygdalina, then spitting out the fibres and swallowing the bitter juices, which are thought to kill parasitic worms. They have also been seen eating indigestible, bristly leaves which make the gut contract, helping to mechanically expel parasites.
Freymann’s work is humbling because it indicates that chimps may have a far better knowledge of the forest’s internal pharmacy than we do. The authors add: “In this paper, we demonstrate how watching and learning from our primate cousins may fast-track the discovery of novel medicines, while also emphasising the importance of protecting our forest pharmacies.”
Main image: Budongo chimpanzee. Credit: Elodie Freymann
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