A group of researchers recently discovered complex bridges that are constructed by Eciton army ants with their own bodies. Researchers said these bridges are constructed to span gaps in the colony’s foraging trail.

According to a paper published Monday in the journal Proceedings of the National Academy of Sciences, the ants also weigh the costs and benefits if making long, living bridges.

Researchers said that if a shorter distance requires large number of ants, then the ants decide that it’s not worth making a bridge. It has been found that army ants build bridges beginning at the intersection between sticks, vines, or other material the insects are walking on.

Ants simply increase the length of the bridge by adding more bodies in order to span a larger and larger space and make a more efficient route, said researchers.

The study shows that ants stop moving the bridge when they sense they are actually slowing their progress overall by using large number of bodies.

Study co-lead author Christopher Reid of the University of Sydney said, “This stopping was a complete surprise for us. In many cases, the ants could have kept the bridge moving to create better shortcuts, but instead they stopped before achieving the shortest route possible”.

Dr. Reid also mentioned that these bridges change dynamically with the traffic pattern on the trail. The team placed boards down on the rainforest floor, creating an angular gap in the ants’ path in order to observe the ants making bridges.

Researchers said they clearly saw ants coming closer one-by-one and forming bridge using their bodies.