[Fast Fact;

Title: These Voracious Ants Are Their Own Mobile Home]. Thanks to Brilliant for supporting this episode. Go to Brilliant.org/SciShow to check out their Introduction to Neural Networks course. [ intro ]. Army ants are formidable, fierce, and fascinating.

They’re perhaps most famous for their aggressive hunting raids. That’s where they get the name, after all. Columns of them a hundred meters long or longer advance out into the jungle to find food, devouring any suitable prey they find.

They’ve been spotted taking on critters many times their size like crabs, lizards, tarantulas, and snakes. They just literally overwhelm things with sheer numbers! But there is a catch to this meaty diet:.

It doesn’t take them long to gobble up the good meal options in an area, forcing the army to move on. And that wouldn’t be an easy thing for most ants to do, since they live in underground burrows that they carefully excavate or mounds that they painstakingly build. So army ants have come up with another kind of nest— one they can take anywhere, because it’s made out of living ants.

These structures are known as bivouacs, and the army starts building one as soon as they arrive in a new spot. This may happen every night if the ants are roaming, or they might settle down in one particular area for a couple weeks. Strands of workers start to form chains and nets by locking the hook-like claws at the end of their feet together and then reflexively freezing in place.

These nets grow larger until they turn into a pouch, curtain, or cylinder-like nest. In some species, hundreds of thousands to millions of workers create a nest that can be a meter or more across. And it isn’t just a big ball of ants.

There’s structure here, including passageways, galleries, and chambers for the queen and her brood. Even the walls are sophisticated, with the larger, stronger, and tougher workers forming the outer wall during the night before climbing down and setting off on raids in the morning. The bivouac has all the benefits of a regular nest, including giving the queen a place to lay eggs, which she does when they’re not roaming.

The bivouac can even help the brood develop. The ants can warm the nest with their body heat, as well as change the shape, or open up or close ventilation channels. This keeps the temperature inside steady and a few degrees warmer than the outside air.

As for how bivouacs and other adaptations for the ants’ fierce lifestyle evolved, well, we’re still learning about that. What we do know is that army ants are essential members of their jungle ecosystems. They’re what ecologists call a keystone species, as hundreds of other species may depend on them in some way for survival.

So scientists are keen to know more about these ants. Researchers are also interested in understanding how individual workers coordinate to build these massive, complex structures. Learning that could help us understand things like how crowds move.

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