How army ants' architecture demonstrates their collective intelligence

ARI SHAPIRO, HOST:

Isabella Muratore at the New Jersey Institute of Technology says studying army ants comes with certain occupational hazards.

ISABELLA MURATORE: They're very aggressive. They have venom, so they will sting you and they will bite you. It's not that bad. It's just that you're usually getting stung by hundreds of them at once.

AILSA CHANG, HOST:

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(Laughter).

SHAPIRO: As she has experienced firsthand, the ants are predators. And as they march through the forest, they gobble up insects - even frogs, lizards and birds.

CHANG: But what's truly remarkable is when the ants encounter obstacles - like, say, a gap between leaves or branches - they build living bridges out of their bodies, hooking themselves together like a barrel of monkeys.

MURATORE: The workers will string themselves across that gap, and then other workers will walk on top of them. Basically, they create shortcuts to make things easier for the other ants or just to allow them to traverse something that they otherwise couldn't.

SHAPIRO: The bridges allow the ants to hunt more quickly and efficiently, but that comes at a cost.

MURATORE: Because the ants that are acting as the structure are not able to also go out and collect prey, but they also have a benefit in terms of saving time for everyone else.

CHANG: Ants have small brains and don't use language, so how do they even make that cost-benefit analysis she describes? Well, Muratore studied the ants' decision-making by deliberately placing obstacles in the ants' way as they navigated the forest. She filmed them, then analyzed the ant traffic.

SHAPIRO: She says the ants build bridges where they get the greatest benefit for the least amount of bodies. She also found that a string of bridges can influence how much ant power the ants are willing to invest in each bridge. She presented her work at a meeting of the Entomological Society of America last week.

DAVID HU: Just like people, we don't just build one bridge, but we have to decide, you know, how is this whole road going to look like across many different obstacles?

CHANG: David Hu at the Georgia Institute of Technology has studied how fire ants use their bodies to build rafts. He says this type of work reveals how ants make collective decisions which could have implications for swarms of robots. Hu says, imagine dumping out a bucket of robot parts which piece themselves together to solve complex problems.

HU: Ants are kind of a - existence proof that, you know, such a robot would actually be able to survive and to have a lot of interesting problems to solve in the real world.

SHAPIRO: Let's just hope those robots don't learn to bite and sting. Transcript provided by NPR, Copyright NPR.