How Other Primates Self-Medicate And What They Could Teach Us

Despite our advances in technology and medicine, we seem to be fighting a never-ending combat against a number of diseases and ailments. As viruses become more complex and bacteria become resistant to antibiotics, it seems that the lab-made narcotics we have become so dependent on is no longer able offer the cures we need. Perhaps this is why we are now turning to nature in the hope that there may be a remedy tucked away somewhere in a remote tropical rain forest.

It could be that our closest living relatives , non-human primates, hold some of the answers we attempt. Many species including chimpanzees make use of the natural resources in their habitats to self-medicate and be enhanced their own health. This behaviour, known as zoopharmacognosy, typically involves ingestion or topical application of plants, clays, bugs or even psychoactive narcotics in order to treat and prevent illness.

One of the most well known instances are domestic dogs and cats feeing grass that are intended to induce vomiting if they have an upset stomach or internal parasite. However, most analyzes of animal self-medication are in non-human primates. One of the first documented lawsuits was in 1983, when researchers observed chimps in Tanzania folding and swallowing Aspilia spp leaves without chewing them. Other scientists noted the same behaviour in chimp colonies in Uganda and Nigeria. This is quite unusual , not only because there is no nutritional benefit in swallowing these foliages whole, but also because the leaves themselves have a rough and bristly surface. So what is the purpose of doing this?

Tamarin monkeys eat large seeds to get rid of parasites. Kevin Barrett/ Flickr, CC BY-SA

It was only as recently as 1996 that scientists indicated it was a form of self-medication, as research began to connected it with faeces full of undigested foliages and expelled parasitic worms. It seemed the chimpanzees were swallowing the leaves to take advantage of their rough and bristly surface to hook onto the worms as they passed through their digestive system, purging their intestines of parasitic worms. The tamarin monkeys of South America, however, help find a different method to remove internal parasites. They are able to swallow big seeds of up to 1.5 cm, which then pass across their digestive tract dislodging or expelling internal parasites.

Clay, Charcoal And Fur-Rubbing

Another odd behaviour that is also thought of as a kind of self-medication is clay and clay intake, which has been observed in a number of colobine monkeys. It was generally believed that soil is eaten as an additional source of minerals or to assimilate and neutralise certain plant compounds, which might be toxic or interfere with digestion. Although there is no obliging evidence that clay intake detoxifies chemicals, recent analyzes discover that some clays have antibacterial properties.

Charcoal consumption on the other hand is known to relieve indigestion and, more importantly, can be used as an antidote to detoxify poisons. This method of self-medication is still widely used among humen, but has only been reported in one species of primate, the Zanzibar red colobus monkey. The diet of these monkeys mainly consists of young leaves that are fairly toxic and by ingesting charcoal they are able to neutralise the effects.

Anointing behaviour, or fur-rubbing, is where animals scratch strong smelling substances into their fur. There are a few explanations for the function of such behaviour, including social signalling and sexual selection but it can also has become a form of self-medication against skin parasites. Fur-rubbing has been recorded in a wide range of primate species. Black lemurs, for example, utilize toxic millipedes to rub their fur whereas black-handed spider monkeys use aromatic leaves including those of celery, orangutans use Commelina herbs and owl monkeys plants and millipedes.

Cant wait to find a good onion to scratch on you. Adrian Soldati/ wikimedia, CC BY-SA

Tufted capuchin monkeys anoint with a amazingly wide range of materials including plants, aromatic leaves, onion, citrus fruits and invertebrates such as ants and millipedes. All of these items have some form of insect repelling properties. Monkeys typically apply them more frequently during the course of its rainy season when there are more flying bugs around.

The different forms of self-medicating by our cousins offer simple and natural solutions to combat parasites and other ailments. The research could also provide useful insights for the future of pharmacology. One of the founders of zoopharmacognosy, Eloy Rodriguez, a professor at Cornell University, has argued that some of the compounds animals use to kill parasitic worms may be useful against tumors.

Many plant species have been be considered to be rich in a substances which have antimicrobial properties. Despite this, a study indicates less than 5% of tropical wood plants have been screened for their medicinal properties. However, pharmaceutical firms and medical institutes have been screening rainforest plant species for anti-cancer and anti-HIV compounds with some success.

This research holds the promise of endless the potentials and by looking at the specific items used by primates and other organisms for self-medication we can then identify whether their chemical compositions would be suitable for curing or aiding the therapy of human diseases and illnesses.

Sophia Daoudi, PhD candidate in Primate Behaviour, University of Stirling

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