Ants Form Living Arks To Weather Floods

Even the smallest of floods may seem like the wrath of the heavens from the perspective of ants. Researchers have found that to survive these cataclysmic events, ant colonies clump into a living arc that can ride on flood-waters until dryer land is found.

According to researcher David Hu, from the Georgia Institute of Technology, simply holding onto one another isn't enough. The ants have to form a structure with mesh-like layers, with the queen of the colony preferably protected in the very center of the "raft."

Even without their queen, red fire ants (Solenopsis invicta) are very adept at somehow launching a mass exodus prompted by rising ground water levels and then creating a raft by holding onto one another in a very efficient manner.

"It turns out that 99 percent of the legs are connected to another ant and there are no free loaders," Hu said in a recent statement.

Hu co-authored a recent study, published in The Journal of Experimental Biology, which details how these ants manage to pull off their impressive feat of group-preservation.

According to the study, the layered and mesh-like ball the ants form hold together using an adhesive force measured to be over 400 times each ant's body weight. The structure is also very flexible, allowing the ant-raft to withstand the ebb and flow of flood-water currents.

"You can consider them as both a fluid and a solid," Hu explained.

He adds that the insects actively orient themselves so they are perpendicular to one one another, creating the flexible mesh.

Hu also explained that the ants have to all be alive to do that, adding, "It requires some intelligence, and suggests that somehow they sense their relative orientation."

Hu and his colleagues discovered all this after gently swirling a jar of floating red fire ants and water. Even amidst the utter chaos of the swirl, 110 of the insects were somehow able to grab hold of one another and quickly orient themselves until they created an arc-like ball.

Most impressively of all, observations of this ball - which was flash frozen after it was formed - revealed that the insects had been actively pushing off one another even as they held on for dear life.

This, Hu explained, creates more air pockets and thus buoyancy even on the deepest of waters.

The study was published in the June 15 issue of The Journal of Experimental Biology.