Ants are incredible diggers, constructing elaborate multi-level nests connected by an intricate network of tunnels, sometimes reaching depths of up to 25 feet. Today, a team of scientists from the California Institute of Technology used X-ray imaging to capture the process by which ants build their tunnels. Scientists have discovered that ants have evolved to intuitively detect particles of grain that they can remove while keeping the structure stable, just like removing individual blocks in a game. jenga. The team described their work for new paper Published in Proceedings of the National Academy of Sciences.
Scientists interested in collective behavior have been studying ants for decades. This is because the ants, as a group, behave like some form of granular medium. A few divergent ants behave as well as individual ants. corn pack enough Together closely and operating as a single unit, they exhibit solid and liquid properties. You can pour fire ants out of a teapot, for example, or the ants can link together to build floating towers or rafts. Ants may be small creatures with small brains, but these social insects are capable of it group organization In a highly effective community to ensure the survival of the colony.
several years agobehavioral biologist Guy Theraulas from the Institute for Advanced Studies in Toulouse, France, and several colleagues combined laboratory experiments with Argentine ants and computer modeling to Define three simple rules Control the behavior of ants by digging tunnels. For intelligence: (1) ants pick up grains at a constant rate (about 2 kernels per minute); (ii) Ants prefer to throw their kernels close to other kernels to form columns; and (3) ants usually select kernels marked with a chemical pheromone after other ants have processed them. Theraulas and others. He built a computer simulation based on these three rules and found that after a week the virtual ants had built a structure very similar to real ant nests. They conclude that these rules arise from local interactions between individual ants, without the need for central coordination.
Recently paper 2020 I found social dynamic The way the division of labor appears in an ant colony is similar to the way political polarization develops in human social networks. Ants are also good at regulating their traffic flow. a Study 2018 Daniel Goldman’s group at Georgia Tech investigated how fire ants can improve tunneling efforts without causing traffic jams. as we are I mentioned at that time, the group concluded that when an ant encounters a tunnel in which other ants are already running, it retreats to find another tunnel. And only a small part of the colony digs at a time: 30 percent of them do 70 percent of the work.
David Ho’s biological locomotion group at Georgia Tech also studied fire ants. in 2019, He and his colleagues reported That the fire ants could actively feel the changes in the forces acting on their floating raft. Ants recognize different fluid flow conditions and can adapt their behavior accordingly to keep the raft stable. The oar moving through the river water will produce a series of vortices (known as fall vortices), causing the ants’ rafts to spin. These vortices can also exert additional forces on the raft, enough to break it. The changes in the centrifugal forces and the shear forces acting on the raft are very small – perhaps 2 to 3 percent of the normal gravitational force. However, one way or another, ants can feel these small changes in their bodies.
This last article focuses on western harvester ants (Pogonomyrmex occidentalis), due to its prolific ability to burrow into millimeter-scale soil grains. Co-author Jose Andrade, a mechanical engineer at Caltech, was inspired to explore tunneling ants after seeing examples of this. Ant’s nest art. The pieces are created by pouring some kind of molten metal, plaster or cement into the anthill, which goes through all the tunnels and eventually solidifies. The surrounding soil is then removed to reveal the final complex structure. Andrade was so impressed that he began to wonder if the ants really “know” how to dig these structures.
Andrade collaborated with Caltech bioengineer Joe Parker on the project; Parker’s research focuses on the ecological relationships of ants with other species. “We didn’t interview any ants to ask if they knew what they were doing, but we assumed they were intentionally digging.” Andrade said. “We assumed the ants might have been playing jenga. “
In other words, the researchers suspected that the ants cleaned the ground for loose grains to remove, in the same way that people search for loose clumps to remove. jenga tower, leaving important support pieces in place. These clumps are part of what’s called a “force chain” that plugs the clumps (or granular soil particles, in the case of an anthill) to create a stable structure.
For their experiments, Andrade and his colleagues mixed 500 ml of koekret soil with 20 ml of water and placed the mixture into several small cups of soil. The size of the wells was chosen based on their ease of insertion into the CT machine. Through trial and error, starting with one ant and gradually increasing the number, the researchers determined the number of ants needed to achieve the optimal digging rate: 15.
The team took four and a half minutes every 10 minutes while the ants were digging a tunnel to monitor their progress. From the resulting 3D images, they create a “digital avatar” for each part of the sample, capturing the shape, position and orientation of each bead, which can greatly affect the distribution of forces in the samples. Earth. The researchers were also able to work out the order in which the ants were removed for each grain by comparing images taken in different states over time.
The ants weren’t always cooperative when it came to seriously digging their tunnels. ‘They are somehow imitated’ Andrade said. “They dig when they want. We’d put these ants in a container, and some would start digging right away, and they’d make amazing progress. But others—it would take hours and not dig at all. Some would dig for a necklace, and then stop and rest.”
Andrade and Parker note some emerging patterns in their analysis. For example, ants usually burrow along the inner edges of the cups – an effective strategy, as the sides of the cups can be part of the tunnel structure, saving them little effort. The ants also preferred the straight lines of their tunnels, a technique that improves efficiency. The ants tended to dig their tunnels as hard as they could. as much as possible in a granular medium as soil is called the “corner of rest”; Exceed this angle and the structure will collapse. In either case, the ants can detect this critical threshold, ensuring that their tunnels do not go beyond the angle of rest.
For basic physics, the team found that when the ants removed soil beads to dig their tunnels, the force chains acting on the structure rearranged from a random distribution to form a kind of coating around the outer tunnel. This redistribution of forces strengthens the existing tunnel walls and relieves the pressure exerted by the granules at the end of the tunnel, making it easier for ants to remove these granules to expand the tunnel further.
“How ants build these decades-old structures is a mystery in both engineering and ant ecology,” he said. parker this. “It turns out that by removing the grain in this pattern that we observed, the ants are taking advantage of oceanic force chains as they burrow.” Ants press on individual grains to assess the mechanical forces acting on them.
Parker thinks it’s a kind of behavioral algorithm. This algorithm does not exist within a single ant. He said. “It is the nascent colony behavior of all these workers who behave like superorganisms. How this behavioral program spreads through the micro-brains of all these ants is one of the wonders of the natural world that we have no explanation for.”
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