Humans can learn a thing or two about efficient delivery from army ants in South and Central America, which form living bridges to shorten their journey on forest floors and fill pesky potholes.

The bio-bridges fill bigger and bigger gaps and create shortcut whenever they bring food home to their whole colony. They stop moving once the lines turn so long, which makes the mounting costs of trapping workers into the system outweigh the gains from shortening the path.

And when do the ant bridges break up? It’s when the creatures part of the structure feel a slowing down below a critical traffic threshold over them.

These were some of the fascinating findings of a team from University of Sydney and other organizations, published in the journal Proceedings of the National Academy of Sciences.

According to co-study lead author and postdoctoral researcher Dr. Christopher Reid, analyzing the utility optimization of ants may help scientists create control algorithms to make robots behave similarly. Swarm robotics can be applied to human rescue operations, for instance.

Dr. Reid’s team discovered that the ant bridges assemble and dissemble in a matter of seconds, and can adjust their position based on the environment. Because of their dynamic nature – previously thought to be static – the bridges allow for maximum-speed travel across potentially risky and unfamiliar terrains.

He explained that once the ants begin at intersections between lianas or twigs they travel, “the bridges slowly move away from their starting point, creating shortcuts and progressively lengthening by addition of new workers, before stopping, suspended in mid-air.”

He added that even if they could create better shortcuts in many instances, the ants would halt their bridges before they achieve the shortest possible route. Why? Owe it to their balancing of a cost-benefit trade-off, where they incur costs by sequestering ant workers that would be useful for other crucial tasks.

The practical side of this research lies mostly on the promise of self-assembling systems. The team plans to work with Radhika Nagpal, a computer scientist from Harvard, to apply this architecture, as nothing yet in robotics combines really fast movement and morphing into the building material itself.

"Artificial systems made of independent robots operating via the same principles as the army ants could build large-scale structures as needed," Dr. Reid said, citing likely tasks that include producing bridges for navigating dangerous areas, and plugs or supports to address structural breaches.

Humans can take their cue from these bridge-building ants in complex situations, such as during natural disasters.

Photo: Matt MacGillivray | Flickr