Ant overboard! The extraordinary flooded fire ant

Introducing the smallest sailors you’ve ever seen.

Listen here for the latest episode of the BBC Earth Podcast. This episode explores what the natural world can teach us about teamwork, in particular the extraordinary behaviour displayed by fire ants when their homes are flooded.

Animals often develop remarkable adaptations and behaviours to live in extreme environmental conditions. But what happens in unstable climates like the Amazon rainforest where the weather can change dramatically in seconds? How have animals learnt to adapt there?

The Amazon rainforest, spanning an area so immense that the UK and Ireland would fit into it an astonishing 17 times, boasts an equally impressive eco-system, with 40,000 different types of plant species and 2.5 million varieties of insect residing there – plus a huge number of species that have yet to be identified.

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Birds eye view of the Amazon rainforest
Weather in the Amazon rainforest can change dramatically in seconds, causing significant flooding. © Kevin Schafer | Getty

There are billions of trees in the rainforest sucking up water through their roots, transporting it to the forest’s canopy, then releasing it into the air as part of a process called evapotranspiration. This water vapour then goes on to form clouds, which eventually release rain and when the rain falls in the Amazon, it comes thick and fast, turning the jungle into one of the wettest places on Earth.

The creatures living here have just two options: climb above the waterline into the trees, or start swimming. But one wily creature has mastered their domain by using ingenuity and, more importantly, teamwork.

Fire ants, named for the burning sting they use for defence, live in large colonies underground, meaning they’re particularly at risk when the rains come. But they’ve devised an impressively nautical solution when their home starts to flood. As the water begins to rise, masses of worker and soldier ants emerge from underground, bringing their queen and larval young with them.

Fire ants floating together
Fire ants form life rafts out of their own bodies to escape flooding. © Silverback Films

Once on the surface, the ants band together, each locking legs with its neighbours, gradually forming a giant raft supported by the surface tension of the water. Ants are covered in fine hairs that trap air against their bodies and that makes this writhing mass of insects buoyant, creating a cushion for them all to float on.

As many as 100,000 insects can form this living raft, which floats for weeks without any ants drowning, thanks to the same air pockets that keep them afloat. The queen and the larvae are kept in the centre – the driest part of this pancake shape – with the other ants providing protection around them.

Biologists and engineers are fascinated with the ability of the ants to suddenly form together into this knitted, floating mass, with the interlocking body parts resembling a sort of biological fabric,seemingly without a leader coordinating the effort. It appears they instinctively know how and when to suddenly coordinate and coalesce.

A formation of fire ants floating

But it’s not all plain sailing. Once they are afloat, they are at the mercy of the current and waves, and can drift for weeks before reaching dry land – if they ever get there at all. Fish and other predators are delighted to see a tasty snack suddenly floating by and, while the ants on the outside of the raft try to defend their cohorts, individual ants can be picked off by hungry locals.

But if they do reach a landing site, they will quickly break off and swarm from the water to safety, carrying the young and the queen. In fact, the ants have turned the disaster of the floods to their advantage, by taking this as an opportunity to travel to new feeding grounds. The ants then wait for the flood waters to recede, before making a new home under the earth.

And when the rains return, the intrepid fire ants will form a raft once more and sail off into the unknown.

Featured image by © Arthit Thi-Ngakhruea / EyeEm | Getty