Self-Medication in our Primate Relatives.

The idea of self-medication in a non-human animal seems a strange one, but there are some animals that do know how to heal themselves.

The idea of self-medication in non-human animals (zoopharmacognosy) is one that is often debated alongside that of intelligence within the animal kingdom, as the individual knowingly utilises natural substances to treat injury or disease. This behaviour has created intrigue across the scientific community since self-medication in the African great apes was observed in the 1980s. Now, scientists from the Orang-utan Tropical Peatland Project have recently documented wild animals using specific leaf extracts to treat inflammatory issues, showing for the first time that Asian great apes having the intelligence and skills to use the local plant matter to treat ailments like pathogens or toxins in the same way the local human population does.

The idea of self-medication in non-human animals naturally re-ignites questions of animal sentience and higher intelligence in primates. Self-medication demonstrates a higher social learning known as ethno-medicine, the research team explains, "as it is known that indigenous communities obtain knowledge of medicinal plants through observing their use by sick animals."

Primates have, historically, been observed using self-medication through the rubbing of certain chewed plant material but research has mainly focused on chimpanzees and baboons. Whilst self-medication has also been observed in the woolly bear caterpillar (Grammia incorrupta), the armyworm (Spodoptera Guenée), the fruit fly (Drosophila melanogaster), the monarch butterfly (Danaus plexippus), and the honey bee (Apis mellifera), it had never been observed in orang-utan's (Pongo pygmaeus).

This new research draws focus to the orang-utan's use of Dracaena cantleyi, which is chewed up and rubbed onto the body because of its anti-inflammatory properties. Researchers from universities in England and Indonesia have observed wild populations of the Asian great ape using this natural medicine, and say they have provided the first evidence for "deliberate external application of substances with demonstrated bioactive potential for self-medication in great apes."

Field work took place in the Sabangau Peat-swamp forest in Indonesia, with the team testing the Dracaena plant matter for specific medicinal properties. The leaves contained saponin, a secondary metabolite, which acts as an anti-inflammatory agent when made into a soapy substance.

Although the researchers write that saponins "tend to be unpalatable, having strong anti-herbivory properties," the chewing and non-digestion of this bitter leaf suggests the orang-utans who self-medicate are knowledgeable about that exact species' biological and medicinal properties.

This work on self-medication in the animal kingdom has implications and discussions that go beyond merely animal behaviour, having a possibly crucial influence on different areas of research. Some medical experts have suggested that this could be applied to treating tropical livestock in more convenient forms and even to combating tumours in humans. The future of zoopharmacognosy and studies into ethno-medicine will aim to determine other cases of self-medication in various animals, how these animals learn these behaviours and how much information on the medical benefits of local substances can these individuals store.

This work demonstrates the orang-utans ability to use "deliberate external application of substances with demonstrated bioactive potential for self-medication." The first evidence for this behaviour in orang-utan's sheds more light onto the amazing medical skills and knowledge that members of the animal kingdom possess.

Author: Thomas Llewellyn

Reference:
Morrogh-Bernard, H.C., Foitová, I., Yeen, Z., Wilkin, P., Martin, R., Rárová, L., Doležal, K., Nurcahyo, W. and Olšanský, M., 2017. Self-medication by orang-utans (Pongo pygmaeus) using bioactive properties of Dracaena cantleyi. Scientific reports, 7(1), p.16653.