Without a set plan or leader, ants are able to construct incredible structures based on collective self-organization. Even in the absence of a consistent leader, this allows them to create entire subterranean cities and structures using their own bodies. Army ants from Central and South America, for example, are renowned for forming living bridges to shorten distances to food.
The ants can not only span gaps with ease, but are also able to dismantle and move their insect bridges within seconds to make foraging more efficient. The feat has been caught on camera by an international group of researchers. By being able to pick up and move their bridges, it allows the ants to travel at maximum speed through an unknown environment, the researchers report in a paper published in the Proceedings of the National Academy of Sciences. The team hopes that understanding how this is achieved could help in the creation of autonomous robot swarms.
Time-lapse of army ants moving their bridge to shorten their foraging route. Chris Reid/The University of Sydney
It was previously assumed that once built, the living bridges were a relatively static structure. The researchers, however, found that this wasn’t the case as they moved in response to changing information and conditions. When the flow of ants crossing it increased, for example, the insects widened it; to shorten the route, they would shift its position. “Indeed, after starting at intersections between twigs or lianas travelled by the ants, the bridges slowly move away from their starting point,” explains Dr. Christopher Reid, co-author of the paper, “creating shortcuts and progressively lengthening by addition of new workers – before stopping, suspended in mid-air.”
Perhaps most importantly, they also found that the forming and moving of bridges required a cost-benefit trade-off. By moving the bridges to make a shortcut, they often had to lengthen it in the process. As more ants were used to build the bridges, it meant that fewer were available for other important tasks, such as finding food. “In many cases, the ants could have created better shortcuts, but instead they ceased moving their bridges before achieving the shortest route possible,” says Dr. Reid.
It is thought that the work carried out on the tiny insects could have implications for other self-building systems, like reconfigurable materials or robotic swarms. This could then have future applications in disaster zones, in which robots could organize themselves to navigate around a tangled, unpredictable setting. “Such swarms could accomplish remarkable tasks, such as creating bridges to navigate complex terrain, plugs to repair structural breaches, or supports to stabilize a failing structure,” explains Dr. Reid.