Two groups of ants in water forming rafts. Scientists color-coded the ants to track individual movements. (Image: UCR)

Ants are amazing at co-operation, using their bodies to form parts of chains, ladders, walls, and even rafts. A new study shows that the rafts built by ants are surprisingly well organized, the product of specialized skills and complex memorization tasks.

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More than perhaps any other species, ants are dependent on each other to achieve tasks far beyond the reach of a single individual. A lone ant is quite useless; but when working in concert with an entire colony, these social insects are capable of extraordinary things. This is why scientists refer to ants as a superorganism. They can’t possibly be understood at the level of the individual.

But it would be a mistake to say that individual ants are unremarkable. Ants have important jobs to fill, and they’re equipped with highly specialized skill sets to make it happen. Such is the case with Formica selysi, a species of ant native to Europe. A team of scientists from the University of California Riverside has learned that these ants, like humans, are capable of working together to improve their response to flooding emergencies. And they do so by virtue executing some fairly specific and sophisticated tasks, and by using their recall abilities.

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A meta-task in which ants use their bodies to create structures or tools is referred to, quite appropriately, as self-assembly. In a study put out in 2014, this same research team discovered that worker ants protected the queen—the most valuable member of the colony—by placing her at the center of the raft. At the same time, the workers placed the immature members of the community at the base of the raft, which contributed to the raft’s stability and buoyancy. Incredibly, the ants exhibited high survival rates after the experience, so it’s not a completely suicidal endeavor for certain members.

But the researchers wanted to learn more about individual ants, and how they worked during self-assembly. To that end, they subjected two groups of ants to two consecutive floods and monitored the position of individuals in the rafts. The researchers watched as individual workers consistently occupied the top, middle, base, or side positions in the raft; using memory, they occupied the same position each time when forming the rafts. Also, the young ants, or brood, contributed by adjusting the workers’ positions and raft shape.

The researchers say it’s the first time that memory has been demonstrated in these self-assemblages. “These elaborate rafts are some of the most visually stunning examples of cooperation in ants,” noted study co-author Jessica Purcell in a statement. “They are just plain cool.”

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[The Science of Nature]