Fire Ants Build Tunnels Like Jenga Blocks

Nature’s top excavator may be the red fire ant, Solenopsis invicta, the invasive, stinging creature that has taken over the lower third of the United States with its intricate mounds, tunnels and homes built with precision in nearly any kind of soil.

The fire ant’s digging prowess taps the same concepts behind kids’ building blocks, according to a new study that looks at the micro-mechanics of their ability to move giant particles in tiny spaces.

“They love to dig,” said Daniel Goldman, physics professor at Georgia Tech and an author on the paper in this week’s Journal of Experimental Biology.

“You can get them to dig in anything. When the particles are big, they grab a grain and remove it. It’s not a trivial task. They have to carefully to hold the particle in their jaw. They have another mode of digging where they can rake and scrape the soil into a pellet, and use their mandibles and antennae in a new way to help shape that pellet.”

Goldman and his colleagues conducted several lab experiments with fire ants using different size particles of sand and tiny glass pellets. They also took X-rays of the ants’ tunnels and found something surprising. The ants carefully constructed the tunnel walls like Jenga blocks, each particle precariously supporting the one on top. When the researchers probed the tunnels with a metal rod, they collapsed, just like the kids’ wooden tower.

“They are doing some nice manipulations that we don’t understand yet,” Goldman told Discovery News.

The research team – which included lead author and postdoctoral researcher Daria Monaenkova – also noticed that the ants built tunnels faster in coarser soils, and didn’t do as well in extremely dry soil as compared to wetter soil.

Since arriving from South America in the 1930s, fire ants have spread throughout the southern United States. In recent years, they have spread westward to Texas, New Mexico and Southern California, occupying an estimated 300 million acres of territory. Their massive colonies contain several hundred thousand individuals, and extend several feet below ground.

Their colonies are considered a “superorganism,” a group of individuals that acts as a single creature. Part of their success is linked to their incredible tunneling abilities, Goldman says, and their ability to squeeze past each other in tiny spaces while carrying big chunks of soil.

Read more at Discovery News