Following the outbreak of COVID-19, countries around the world adopted public health measures including national lockdowns, social distancing, and travel restrictions. The idea is to avoid close contact to reduce the spread of the virus. But it seems that humans are not the only ones who change their space environment to reduce the risk of epidemics.
A new study published in the journal Science shows that black ants (Lasius niger) change the structure of their nests to slow outbreaks—an insect version of social isolation that is cleverly integrated into the walls of their nests.
Luke Leckie, lead author of the study from the University of Bristol, explained that ants are known to change their digging behavior depending on soil temperature and composition. However, Lackey said, "This is the first time that non-human animals have been shown to reduce disease transmission by changing the structure of their environment."
In animal groups, especially eusocial insects like ants, tight networks of social contacts facilitate the spread of infectious pathogens. Because ant nests are known for their high complexity, with chambers dedicated to storing food, larvae, and excrement, the researchers speculate that their underground network effectively isolates potential sources of infection.
To test this hypothesis, Leckie and his colleagues used an advanced three-dimensional scanning technology called micro-computed tomography (micro-CT) to observe two groups of 180 black ants digging nests in soil-filled containers. After 24 hours, the research team placed 20 ants in each container, and one group of ants was exposed to spores of Metarhizium brunneum. Over the next six days, scientists scanned each nest regularly to obtain three-dimensional images of every tunnel, entrance and room.
Using three-dimensional models, the team found that ants exposed to fungal spores adjusted their nest layout more frequently. The average distance between nest entrances increased by about 6 millimeters. Increased spacing between entrance areas means fewer crowded spots on the surface of the nest.
Colonies exposed to pathogens also build cells in remote locations with longer, more tortuous paths. Ants even dig multiple tunnels, which may be alternative transportation routes to avoid contact. The study also documented increased activity on colony surfaces in worker ants exposed to the pathogen, which may reflect their self-isolation and social distancing behaviors.
The researchers then used spatial network analysis and 3D model-based simulation of disease spread. The analysis showed that the redesigned nests successfully reduced the risk of infection to individuals.
"One of our most surprising findings was that when we included the self-isolation behavior of ants in our simulations, the effect of self-isolation in reducing disease transmission was stronger in nests exposed to the bacteria than in control nests," Luke said.
The study was published in the journal Science.