© The Independent, UKFindings of study raise questions over how ants 'know' they are sick.
Scientists have shown that ants with a life-threatening fungus are able to "self-medicate", eating a normally harmful substance that treats the condition.
This form of "self-medication" in insects has been suspected in research circles but has never been proven until now, raising questions about how the ant "knows" it is sick.
Researchers at the University of Helsinki in Finland showed that ants infected with the fungus Beauveria bassiana would choose to eat small doses of hydrogen peroxide, which had been proven to reduce their deaths by at least 15 per cent.
The fact that most healthy ants gave the poison a wide berth - since it usually caused a 20 per cent mortality rate - appeared to show that sick ants knew the poison would help them recover.
Depending on how strong the toxic solution was, the infected ants would also either choose to eat the poison as often as normal food, or only a quarter of the time, showing they were "careful" about their selecting their doses.
Nick Bos, one of the researchers, said ants close to death in the wild also seem to know because they often leave the nest to die in isolation.
Comment: The exposure to these drugs not only poses a potential risk to the health of wildlife but may be changing behaviour and physiology. Pharmaceuticals are designed to alter physiology at low doses and can be particularly potent contaminants. It is also now emerging that pharmaceuticals and their bio-transformation products are present in a range of habitats, some can bio-accumulate and may have significant, but largely unstudied, consequences for individuals, populations and ecosystems.