A team of researchers in Australia recently filmed ants while the tiny creatures were busy constructing bridge to fill gaps and create shortcuts in the floor of the tropical forest of Central America.
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Army ants lock their bodies together to create the bridges, assembling and disassembling in seconds. When building their bridges, army ants have to meet this cost-benefit tradeoff, and therefore can not build long bridges between distant parts of their trails without risking lacking workers elsewhere.
An global team of researchers has now discovered these bridges can move from their original building point to span large gaps and change position as required.
Army ants are nomadic species which relocate their colonies throughout the rainforest on regular basis.
The bridges dismantle once the ants making the structure sense the traffic walking over them slows down below a critical threshold.
The bridge will stay in place until the crossing traffic slows, and the costs outweigh the benefits.
Researchers hope that understanding the utilities of army ants will help them develop swarm robotics, for exploration and rescue operations by applying similar behaviors.
“Indeed, after starting at intersections between twigs or lianas travelled by the ants, 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”, Dr Reid says.
“In many cases, the ants could have created better shortcuts, but instead they ceased moving their bridges before achieving the shortest route possible”, Reid added.
The team included researchers from the University of Sydney’s Insect Behaviour and Ecology Lab, the Max Planck Institute for Ornithology, the University of Konstanz, the United States’s New Jersey Institute of Technology, Princeton University and George Washington University.
Reid and his collaborators discovered that, while ants benefit from shorter traveling distances thanks to their living bridges, they also incur a cost by sequestering workers that could be used for other important tasks, such as prey capture or brood transportation. Prior to the study it was assumed that, once they had been built, the bridges were relatively static structures.
Dr Reid said the principles of the findings have implications for other systems such as swarm robotics.
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“Such swarms could accomplish remarkable tasks, such as creating bridges to navigate complex terrain, plugs to fix structural breaches, or supports to stabilise a failing structure”.
