In an anthill, thousands of people live in promiscuity. This density and the frequent contacts between individuals are favorable to epidemics. But ants are able to react when a microbe enters the anthill, say UNIL researchers in a study published in the journal Science.
"It's immediate, they are able to detect the pathogen now and respond, infected ants will isolate themselves, others will try to heal them and help them get rid of fungi, and they will also rearrange between them to reduce transmission in the colony, "says Nathalie Stroeymeyt, author of the study.
Protect the heart of the colony
The biologist studied 22 colonies of a common species, the black ant of the gardens. Each of the 2266 individuals was identified using a digital marker. Photos taken every half second registered movements and contacts between animals in the presence of a pathogen, in this case fungal cells.
The results are formal: insects change their behavior only one hour after infection of the first worker. The trade of infected ants declines to protect the heart of the colony, the queen and the young.
"Young workers are more important because they still have a lot of work to do in the community and if there is a risk of contamination, ants make them run for the elderly who are nearing the end of their lives. "explains Nathalie Stroeymeyt.
The biologists confirmed that mortality was indeed higher among forages, older and specialized in foraging than among the nursing mothers, remained close to the queen and raised. All the queens survived.
70 million years ahead of man
This strategy of controlling epidemics adds to other behaviors known in ants to protect against disease. In the colony, the insects separate the clean activities of the dirty ones creating cemetery and disposition of residues, as in humans.
The only difference, says the director of UNIL's Department of Ecology and Evolution Laurent Keller, "is that the ants do this 70 million years ago."
Aurélie Coulon / fme