But residents may notice something else floating around in the water: Buoyant hordes of fire ants clinging to each other to survive.
A television reporter from the FOX Carolina news station in South Carolina noticed what looked like a patch of mud floating in Greenville County on Sunday.
But when he got closer, he realised that it was a living, breathing life raft made up of hundreds — likely thousands — of fire ants:
While this may seem strange, it’s actually very common. A single ant by itself would struggle to stay afloat in water, but when they band together as a team, sometimes more than 100,000 strong, they can link their appendages and float on their self-assembled life raft for weeks or even months with minimal effort.
This ability hasn’t come as a surprise to scientists, given ants’ impressive teamwork in building nests and foraging for food. But how they stay afloat has puzzled biologists for years.
To better understand how the raft works, a team of scientists from the Georgia Institute of Technology in Atlanta used time-lapse photography to scrutinize the dynamics of the raft. They published the results of their study in the Proceedings of the National Academy of Sciences in May 2011.
After collecting colonies of fire ants from roadsides in Atlanta, the team allowed them to assemble into a raft and then froze the entire assemblage with liquid nitrogen. After analysing the brittle, frozen clump, they found that fire ants use their mandibles, claws, and the adhesive pads on the ends of their legs to grab onto each other.
The firmness of their grip was impressive. The team calculated that each ant’s grip strength was equivalent to a force 400 times its body weight. This grip is twice as strong as the force it needs to stick to glass.
Then the scientists tested the ants’ water resistance and buoyancy by analysing how water behaves when dropped onto their bodies.
An ant’s exoskeleton can repel water, the researchers found. And an ant is also able to trap a thin layer of air against its body. This oxygen strip helps them stay afloat, and it also acts as a gill that lets them breathe when they’re the unlucky ones strapped to the bottom of the raft.
Fire ants have adapted to maintain the integrity of their colony by utilising this innovative survival technique during floods. In water emergencies, they can strap the queen and larvae onto the top of the raft to preserve the precious cargo.
Check out the entire video of the South Carolina ant raft here: