Do you want your coughing, your sneezing colleagues stay away from the office? Unlike some people, ants seem to understand the importance of avoiding others when they are infected. When the ants are exposed to a fungal pathogen, they reduce their contact with the workers inside the nest.
Nathalie Stroeymeyt of the University of Lausanne, Switzerland, colleagues studied colonies of Lasius niger ants using an automated ant-tracking system.
Workers in these colonies are split into nurses, who work inside the nest, and foragers who collect food outside the nest. Foragers are most likely to pick up infections, but they interact less with other ants and come in contact with those inside the nest infrequently.
The researchers exposed some of the foragers to spores of Metarhizium brunneum fungus. The spores attach to the ant's cuticle and after a day or two, the fungus gets inside the ant and kills it.
Within one day of exposure to the pathogen – before ants became ill – the separation between work groups was reinforced. Exposed foragers have changed their behavior, spending even more time outside the nest and decreasing their contact with other workers. Foragers who were not exposed to the pathogen also took steps to isolate themselves, and the nurses moved the brood deep inside the nest.
It is not clear how ants recognize the infection, but they may be able to detect spores on other ants as well as on their own bodies.
Simulations show that these changes in behavior reduce the spread of infections and protect healthy workers and the queen from disease.
Reasons like this are to be expected in social insects, since only the queen reproduces, so evolution favors an individual behavior that benefits the entire colony.
"I think we could learn from social insects about ways to reduce transmission of disease at the scale of the population," says Stroeymeyt. Although she admits that the ants are good role models only up to a point. "We can not really ask sick people to sacrifice themselves by dying in isolation like the ants do."
Journal reference: Science , DOI: 10.1126 / science.aat4793
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