Ants self-medicate on toxins when sick (Wired UK)


Ants know how to self-medicate, and consume toxic substances to fight fungal infections. 

This finding was made by a team of biologists from the University of Helsinki, which decided to poison healthy ants with harmful hydrogen peroxide to prove the theory. The team wanted to show that a healthy ant would never ordinarily consume the substance, because of its toxicity, and that any consumption in the wild — post-infection — was in fact a deliberate act of self-medication.

An article in the New Scientist explains how the team gave the Formica fusca ant species a diet of either a honey solution, or one tainted with hydrogen peroxide. Those inadvertently enjoying the latter had a 20 percent chance of death versus the other group, which had a 5 percent chance. Carrying out the exact same scenario, but this time with ants infected with a fungus, the scientists found the mortality rate went from 45 percent in the hydrogen peroxide diet group to 60 percent in the pure honey solution. The key to the team’s study, however, was when the ants had a choice of either the honey- or toxin-laced solution, those with the fungus went for the latter. These same ants were also very careful about how much of it they consumed, depending on whether the dose was a strong or weak one, suggesting they were very much aware that it would all be over anyway if they consumed too much.

“Here, we show for the first time that ants selectively consume harmful substances upon exposure to a fungal pathogen, yet avoid these in the absence of infection,” the team writes in the International Journal of Organic Evolution. “The fact that ingestion of this substance carries a fitness cost in the absence of pathogens rules out compensatory diet choice as the mechanism, and provides evidence that social insects medicate themselves against fungal infection, using a substance that carries a fitness cost to uninfected individuals.”

“It is not known yet how ants know they are infected, but it’s very clear that they do somehow change their behaviour once they are,” Nick Bos, coauthor on the study paper, told the New Scientist.

This is not the first time the phenomena has been identified in an insect population. Fruit flies, for instance, have been shown to lay their eggs in fruit containing higher levels of alcohol (due to fermentation) to fend off nearby parasitic wasps and increase the survival rates of the offspring — a higher blood-alcohol content tends to kill off parasitic wasp maggots. 

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21 August 2015 | 4:06 pm – Source:


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