Scientists have observed Bornean orangutans chewing on the leaves of the Dracaena cantleyi plant, producing a soapy lather they then spread onto their skin.

A new study finds D. cantleyi has anti-inflammatory properties, suggesting the orangutans are using it to self-medicate.

Indigenous communities also use D. cantleyi as a pain reliever.

The researchers say their study provides the first scientific evidence of deliberate, external self-medication in great apes.

The natural world is full of medicines, many of which have been tapped by pharmaceutical companies to derive products that adorn our drugstore shelves and bathroom cabinets. But humans aren’t the only animals that can find and apply medicinal substances, and now new research adds orangutans to the growing list of species that self-medicate.

Examples of self-medicating animals aren’t exactly uncommon. Some birds engage in “anting” by rubbing ants over their bodies; scientists think the formic acid produced by ants may be used by birds as a fungicide or bactericide. Capuchin monkeys have been observed rubbing their fur with plants that have anti-insect properties. And researchers believe chimpanzees often swallow whole the leaves of bitter plants they normally wouldn’t eat in order to rid their bodies of nematodes.

But never before has this behavior been confirmed in Asia’s great apes, the orangutans. A study published last week in Nature upends this, showing that a plant used by Bornean orangutans (Pongo pygmaeus) does indeed have anti-inflammatory properties. Its authors say their results indicate that the apes likely use it for its medicinal benefits and provide the first scientific evidence of deliberate, external self-medication in great apes.

The plant is Dracaena cantleyi, a nondescript species with big leaves found in Southeast Asia. Its leaves contain saponin, a chemical compound that generally makes them bitter and unattractive as a food source.

Saponin foams when agitated and, despite its bitterness, scientists have observed Bornean orangutans chewing D. cantleyi leaves and making a soapy lather that they then spread on their skin.

The orangutans spit out any leaves they didn’t apply to their skin, which made scientists believe they weren’t simply eating them. But they didn’t know for sure if D. cantleyi had any medicinal properties that would help explain the behavior. To answer this question, a team of researchers from various institutions around the work set to work to figure out if the plant contained anything that might explain why orangutans are braving its bitter taste to make it into a salve.

Their pharmacological analysis indicated D. cantleyi has anti-inflammatory properties. Most orangutans observed using it were females who spread it onto their arms, and the researchers suggest they may have been using it to treat arms that became sore from carrying offspring.

Residents of human communities in Borneo reportedly also use D. cantleyi to treat joint and muscle pain.

“The fact that local people use the crushed leaves for sore muscles and joints further supports the concept that orang-utans would use it to treat similar problems,” the researchers write in their study. “Local indigenous people in Borneo, for example, use it to treat pain in their arms after a stroke, for muscular pain, and for sore bones and swellings.”

The researchers say their results could also aid the study of indigenous medicine.

“This finding is also important for studies of ethno-medicine, as it is known that indigenous communities obtain knowledge of medicinal plants through observing their use by sick animals.”

Citations:

Morrogh-Bernard, H. C., Foitová, I., Yeen, Z., Wilkin, P., Martin, R., Rárová, L., … & Olšanský, M. (2017). Self-medication by orang-utans (Pongo pygmaeus) using bioactive properties of Dracaena cantleyi. Scientific Reports , 7 (1), 16653.

, (1), 16653. Banner image by Rhett A. Butler / Mongabay

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