Army Ants Build Living Bridges

Army ants build bridges out of themselves.

When a colony of Eciton burchellii is on the march in Central and South America, workers link legs and jaws to form a living chain across gaps. Other ants then run across their bodies like a highway.

In 2017, researchers filmed colonies and found ants constantly adjust the bridge. If traffic jams, they add ants to widen it. If the gap is too large, they dismantle it and find another route. They perform a cost-benefit calculation: a bridge saves time, but every ant in the bridge is not foraging.

A single colony can contain 2 million ants and may build hundreds of bridges per day. The bridges are self-healing - if an ant is knocked out, others fill the hole in seconds. It is the only animal besides humans known to dynamically resize a structure based on real-time traffic.