We humans have been using self-medication to cure the illnesses since the dawn of our species. There is some evidence that also other animals can exhibit this type of behavior, but the evidence has been hard to come by.

Scientists from the University of Helsinki, Finland, have now shown that black ant Formica fusca can change their taste for food once exposed to the fungal pathogens. In the compound of interest was hydrogen peroxide, which can be found in the damaged plants, other insects and cadavers.

"When ants are feeding on the diet containing extra free radicals they are able to survive infections significantly better. Moreover, the ants also choose the diet including extra free radicals after they are exposed to fungus, but not if they are not," says University researcher Dalial Freitak from the Faculty of Biological and Environmental Sciences.

"It is amazing discovery that ants have an idea of their health status and seem to adjust the dosage of medicine to that," continues a fellow researcher Nick Bos.

For healthy individuals under no infection conditions, feeding on the free radical diet has the same detrimental side-effects as with any drug. But once infected, free-radical-feeding ants have about 20% higher chances to survive the otherwise lethal fungal disease.