When flood waters threaten their underground nests, fire ants order an immediate evacuation. They make their way to the surface and grab hold of one another, making a living raft that can sail for months.
The extraordinary survival tactic, which can involve entire colonies of more than a hundred thousand ants, has been captured on film by US engineers who used the footage to help unravel how the insects co-operate to overcome nature's dangers.
Film of the ants in action reveals that pockets of air get trapped between them and around their bodies, helping them breathe if the raft is pushed under the water. In normal circumstances the ants lock legs, and sometimes mandibles, to form a floating mat that sits on top of the water through a combination of surface tension and buoyancy.
"Even the ones at the bottom remain dry and able to breathe because they are not actually under the water," said Nathan Mlot, a PhD student at Georgia Institute of Technology in Atlanta. The species of ant, Solenopsis invicta, is native to the Brazilian rainforest, where flash floods are an ever-present danger. In the wild, vast rafts of ants can survive by floating along waterways until floods subside or they reach land.
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