By Jack Williams
This fascinating footage shows the algorithms used by army ants to build BRIDGES with their bodies.
A new study, co-authored by Simon Garnier, director of the Swarm Lab at the New Jersey Institute of Technology, has helped shed light not only on how an army ant colony builds bridges, but also how they may even opt to build bridges themselves.
For the process itself, when a leading ant initially comes to a gap in its path, it will begin to slow down.
The remainder of the colony, however, will continue on their path, swiftly, heading over top of the leading ant.
At this point, the previous leading ant will freeze altogether, and the next ant in line will be faced with the same predicament, slowing down to face the oncoming gap.
That ant will then also freeze, allowing another ant to head over top of it – a process that repeats again and again, ant after ant, creating a bridge-like structure of frozen ants.
Simon said:”In the past, there has been a lot of descriptive work of the structures built by these ants.
“The originality of our work was the creation of experimental setups that we could bring to the tropical forest in order to experimentally control the conditions under which the ants build bridges to shortcut deviations along their trails.”
In field tests in Panama, Simon and collaborators, Chris Reid and Matthew Lutz, also looked into how ants will prioritize where to build their bridges.
The group used a V-shaped structure for the tests, and the colony, which did not wish to head all the way around, initially built a bridge close to the angle of the V.
What comes next is an unconscious trade-off of how wide to build the bridge: The colony does not want to commit too many ants, but it also wants the journey to be as short as possible.
In 2015, Garnier and colleagues calculated that up to 20 percent of a colony may be locked into bridges on a route at any time.
This is when an individual ant may run a “bridging” algorithm.
An ant can tell how many times it has been stampeded by previous ants, judging the width of the bridge.
When this hits a certain number, an ant – judging too many ants in the colony may now be occupying bridges – may rejoin the march.
Such findings and bridge-construction algorithms are also being looked into by the engineering community.
Simon said: “Our last study was a collaborative effort involving Jason Graham (Scranton University), Albert Kao (Harvard University) and Dylana Wilhelm (undergraduate student at James Madison University). STUDY: https://www.ncbi.nlm.nih.gov/pubmed/28939347)
“The response has been very positive, I think. In the past, there has been a lot of descriptive work of the structures built by these ants.
“The originality of our work was the creation of experimental setups that we could bring to the tropical forest in order to experimentally control the conditions under which the ants build bridges to shortcut deviations along their trails.
“We have also received positive feedback from the engineering community, with researchers now looking into using our findings to design self-assembling robots for various applications, such as self-repairing structures.”