Road rage keeps ants moving smoothly

Traffic scientists, specialists in nonlinear systems, and animal behaviorists have cooperated in a study of one of the natural geniuses of transportation engineering: the black garden ant of Europe.

A BRIDGE TOO NARROW. In a traffic experiment, ants from a nest (left) cross a split-lane bridge to collect a sugar solution. Nature

Ants don’t have police officers or traffic lights, but crowded streams of workers readily redirect themselves into new traffic patterns that ease congestion, according to Audrey Dussutour of Paul Sabatier University in Toulouse, France. “They regulate traffic before it becomes blocked,” she says.

She and her colleagues set up a pathway that forked and then reunited into a single lane leading to an alluring sugar solution. When the researchers made each branch of the fork an ample, finger-width freeway, the hundreds of ants in a nest linked to the course tended to do all of their traveling on just one branch of the fork. That’s presumably because the first ant to enter the path left behind a trail of scent and the rest followed, all the while reinforcing the scent.

When the researchers narrowed the branches to 6 millimeters or less, traffic got so dense that ants started to collide head-on. Pushing and shoving then nudged some ants at the forks in the road toward the underutilized branch. Both branches soon carried two-way traffic.

This mechanism of congestion control among ants could point to new ways of routing data in networks, Dussutour and her colleagues point out in the March 4 Nature.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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