Natures wonders: ant raft movements & shenanigan's (Introduction)

by David Turell , Wednesday, June 30, 2021, 19:22 (1031 days ago) @ David Turell

New studies watch how the individuals and the whole raft make moves, even escaping the tank!:

https://www.smithsonianmag.com/science-nature/floating-fire-ant-rafts-form-mesmerizing-...

"Fire ants also swarm, but with a slightly different form. They will clump into a floating raft when they encounter a body of water, but they don’t always stick together into a tight glob. Sometimes, a handful of capricious ants will wander out from the middle safe zone and willingly throw themselves off the edge of their cluster, forming finger-like protrusions over the water. This previously undescribed, projection-producing behavior can persist for hours, as reported in a study published today in Journal of the Royal Society Interface.

"Animal groups are tight balls for a reason. “Anything that’s sticking out could get cut off,” says David Hu, a mechanical engineer at Georgia Institute of Technology who wasn’t involved in the study. He was surprised by the article's finding, as ants also usually stay close to their queen. Those severed from their raft won’t survive, “so it does seem like a risk to the ants,” says Hu. Yet the ants seem to be making these moving fingers—up to eight inches long—without fail, researchers found.

"Many insects are veritable engineers, working together to build mighty structures. But few species assemble like the fire ant; they use their bodies as construction material simply by gripping each other with their jaws, claws and sticky legs—the ant equivalent of holding hands. Alone, a fire ant is nothing spectacular. But lump them together, and the insects behave with what is called swarm intelligence; individuals work as a team, obeying simple rules to give rise to far more complex collective behavior. (my bold)

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"Protrusion formation probably helps fire ants search their environment for new ground in a flooded environment, akin to casting a wide net and hoping something catches, says Linda Hooper-Bui, an environmental scientist at Louisiana State University. “They've never been described the way [the researchers] described them, that was very novel,” she says. From an environmental perspective, she says that the study is important to help scientists better understand how these ants get around and establish new footholds in the wild, especially after a flood. “The more we know about them, the better,” she adds. (my bold)

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"When Vernerey’s team looked closely at the raft, they noticed the structure’s innards were churning. The raft seemed to be made of two distinct layers: the ants buoying the raft underneath and the topside ants tromping over their supporting comrades. Ants on the top of the raft would roam off the edge, to start or contribute to growing protrusions. The ants in the submerged half would eventually crawl out from beneath and through the middle of the raft to replenish the topside ants. The circulation of ants within the raft is what the researchers call “treadmilling.”

“'The whole thing is kind of like a doughnut-shaped conveyor belt,” says Robert Wagner, a materials scientist at the University of Colorado, Boulder and the lead author of the study. He calls the ant swarm “a fluid over really long timescales.”

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"Fire ants are also crafty escape artists, partly thanks to the swarm’s ability to probe with protrusions. After an overnight experiment, Wagner returned to the lab the next morning, only to find the water tank on his table ant-free. His video footage showed that the amoeba-shaped colony had extended one of its arms far beyond the camera frame, probably finding a promising escape route along one of the tank’s side walls. He watched as the blob of ants seeped across the video screen along the protrusion, eventually disappearing from the frame entirely. The next thing he saw was the blurry silhouette of ants in the foreground, marching outside of the container. The stowaway swarm had snaked its way across the water to freedom—only to roost in one corner of the table in a docile clump."

Comment: Note the bolds. The individual ant follows simple rules for himself to create the whole raft behaviour. The escape reminds me of the escaping octopus. The protrusions obviously find new avenues to explore. No overall controlling mind, but swarm action based on programmed individual responses. Videos are a must see.