How ants work together to survive floods

Fire ants are a major hazard in the Southern US. Whether you stumble onto a colony of these tiny stinging demons or simply stand too near a nest, you’ll likely end up with painful reminders of how appropriately these insects are named.

The mounds – which can approach a density of 1,000 per acre – are usually 1 to 3 inches tall and made of soft dirt, but can sometimes approach a full 12 inches in height. It’s not unusual for a medium-sized nest to hold tens of thousands of ants.

Among environments fire ants like to construct nests is along riverbanks and around ponds. As someone who likes to fish, I’ve discovered many a fire ant nest the hard way.

So, while I have a soft spot for most living things, it is with a child-like glee that, after a day of fishing, I will take occasion to carefully kick ant nests into the water when the opportunity presents itself.

The way I see it, anything that can harm me or my kids – along with any other living creature unfortunate enough to blunder along – is fair game. And if I can help cut down on these invasive pests, even better.

One thing that always caught my attention was how the ants, after being punted into the drink, would cling together. This is no accident, according to a recent study released by scientists from the University of Lausanne in Switzerland.

When faced with a flood, ants use their own bodies to form a raft and rely on the buoyancy of the brood and the recovery ability of workers to minimize injury or death, according to the study, released earlier this week. In addition, the queen ant is placed in the middle and protected on all sides by the rafting ants.

“Researchers found that the worker ants and brood were extremely resistant to submersion,” according to the website RedOrbit. “The workers protected the most vulnerable and valuable nest mate, the queen, by placing her in the center of the raft, and the worker ants used the buoyancy of the brood (containing developing larvae and pupae) at the base and recovery ability of workers to create a raft and minimize ant injury or death.

“Both workers and brood exhibited high survival rates after they rafted, which suggests that occupying the base of the raft is not as deadly as scientists expected,” the website added. “Placing the brood at the base of the raft may also aid in keeping the nest together during the flood.”

It is known that social animals often work together to enhance the survival and welfare of the group. The process of how ants work together to survive floods was known but not fully understood, prompting the Swiss researchers to undertake their project.

The scientists collected ants from a flood plain in Switzerland and brought them back to the lab where they could induce flooding in ant populations containing different combinations of worker ants, queens and broods.

During the “flooding,” they observed where the workers, brood, and queens were positioned in the raft. The flooding also allowed them to observe the buoyancy and recovery ability of the worker ants and brood, according to RedOrbit.

“We expected that individuals submerged on the base of the raft would face the highest cost, so we were astonished to see the ants systematically place the youngest colony members in that positions,” said Dr. Jessica Purcell from University of Lausanne.

“Further experiments revealed that the brood are the most buoyant members of the society and that rafting does not decrease their survival; thus, this configuration benefits the group at minimal cost,” she added.

All of which means that my many years of attempting to exterminate fire ants have likely only made them madder.

(Top: Fire ants “rafting.”)