A few years ago, a group of researchers found a female lemur partaking in a strange ritual. In her left hand, she held a millipede, which had been freshly dug out of the ground. The lemur put the myriapod in her mouth, chewing it up until an orange fluid came out. She then vigorously rubbed the oozing fluid on her genitals, her anus and her tail. After a short pause, she finally ended her ablutions by swallowing up what remained of the millipede.
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The team led by Louise Peckre, who is behavioural ecologist at the Leibniz Institute for Primate Research, was obviously not left indifferent by this encounter. The researchers followed two groups of red-fronted lemurs (Eulemur ruffirons) in the Madagascan forest of Kirindy to try to find out more about this fascinating and somewhat revolting practice.
In their study, which appeared this week in the journal Primates, the research team expose their fascinating conclusion: these lemurs chewed up millipedes for medical reasons, and not for nourishment or to satisfy a guilty pleasure. Rubbing themselves with the chewed remains allowed them to cure themselves, or at least to protect themselves against intestinal diseases, in a form of self-medication. But the unexpected reason for this behaviour had yet to be proved.
Covering the body in fluid is a common practice among primates
Covering the body with a nauseating substance is a widespread practice among primates. According to an article by Sophia Daoudi, a PhD student researching primate behaviour, which was published on the website The Conversation, this practice was observed for the first time in the 1980s. Since then, members of different species were spotted performing a similar kind of behaviour.
'It’s not something that has been observed much in lemurs before, but it’s a group in which I’d expect to see it happening—they’re very curious and very smart,’ declared Ian Taterstall, an anthropologist and lemur expert at the American Natural History Museum, who was not involved in the new study.
But the motivations are not always clear, and this kind of behaviour does not necessarily hint at self-medication. In the case of these groups of lemurs, several factors allowed researchers to declare that the practice was medicinal.
A natural insecticide provided by millipedes
The body of a millipede is covered with toxic substances which repels predators. These chemical substances include a category named benzoquinone, which is known for its ability to drive away insects. The benzoquinone can also help protect individuals against diseases caused by mosquito bites, such as malaria and yellow fever.
Even if high doses of these chemical products can be toxic for primates, the immediate benefit is well worth the risk. The problem is that red-fronted lemurs do not seem to be infected by diseases carried by mosquitoes. The insects would be more likely to attack the exposed face rather than their tail or genital organs.
On the other hand, lemurs are much more sensitive to intestinal worms, which can cause eczema and ... an itchy backside. After closer inspection, the researchers found that many lemurs had bald spots on the lower back - signs of irritation and frequent rubbing.
The millipede transformed into edible soap
Louise Peckre advanced a hypothesis that lemurs use millipedes to kill two birds with one stone. By self-anointing with secretions, they kill parasitic worms where they are the most easily transmitted, in the area of the tail and anus. And some lemurs even make an additional effort , by eating the myriapod and its toxic products to get rid of residual infections caused by parasites.
‘The self-anointing of the body, combined with the ingestion of the millipede’s secretions, is a practice of self-medication,’ declares Louise Peckre in a communiqué for the German Primate Center. But further research is necessary to confirm that benzoquinone is effective in tackling parasitic worms.
It would also be worth checking that the upsurge of this practice is aligned with the season in which parasites are most active. In any case, such a practice shows us the extent to which lemurs are sensitive to their wellbeing. Would you go to such extremes as rubbing yourself with toxic substances to stay in good health?
