Ants that construct turrets for their nests choose what to build them with in an architecturally sound way, even when given unfamiliar materials.
South American leafcutter ants (Acromyrmex fracticornis) carry plant clippings into underground chambers where they use them to cultivate fungus for food. To promote fungal growth, they build thatch-like turrets that keep rainwater from flooding their nests and that create the correct humidity level.
In their natural environment, the ants select thick wooden sticks for the base of the turrets, overlapping them like a log cabin, and lightweight grass for the top, then plaster the interior with clay pellets. The whole process takes three days.
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“They try to keep [the nest] at about 25°C for the fungus and then really high humidity,” says Daniela Römer at the University of Würzburg, Germany. “Putting plant fibres on top prevents against humidity loss.”
To test how the ants choose their building materials, Römer and her colleagues replaced their regular choice of twigs and fresh grass with slivers of processed smooth wood and dry grass. They found that the insects still made the same decisions with these new materials, selecting for thickness at the base and lighter vegetation, which promotes humidity, at the top.
This illustrates how relatively simple animals can use social organisation to create complex structures, says Römer.
“They just react to what is right in front of them,” she says. “They’re not thinking of what they’re building or how it’s supposed to look. But by organising their behaviour in the whole colony, reacting to each other’s cues and cues from their environment, they actually manage to build very complex structures that you wouldn’t expect such simple animals to be able to do.”
Royal Society Open Science
