Author | Source of the sky
Edit | Sad thallium baby
Source | I am a scientist iScientist
Ants have an ability that is very envious of road addicts: they will not get lost.
Unlike wandering insects, ants that live in groups have fixed nests and need to frequently travel to unknown areas to find food and bring them home. Therefore, for ants, the ability to recognize the way is just needed.
The mediocre little genius who recognized the road | Pixabay
How do ants recognize the way?
Humans memorize routes in the form of spatial imagination or literal encoding, while ants do so through a process called path integration.
Path integration is somewhat similar to the mathematical vector addition calculation. When ants start moving from a starting point (such as a nest), every time they pass a small distance, they will judge the direction and distance of the current position relative to the previous position through sensory information such as vision (such as the position of the sun), and store this path in the form of a "vector" in the brain.
By superimposing these vectors, the ant can estimate the relationship between the current position and the starting point. Therefore, no matter how tortuous the route is, the ant can copy the straighter short road back on the way back.
Path integral | Wikimedia Commons, author of Chinese
So the problem arises: although path integration can make ants find their way home, the surrounding environment is sometimes very complex and changeable.
So, if you have encountered an obstacle or predator on the calculated return route, and when you pass by again, will the ants continue to take this short path, or will they choose a new path to bypass?
The answer is: case by case.
The team of Antoine Wystrach of the Centre for Animal Cognition Studies at the French National Research Centre studied the problem and published the results in Contemporary Biology in April 2020. In this study, they found that desert ants can combine route memory with negative memory to optimize their walking route through the learning process.
Specifically, some ants have bypassed the trap; some ants that have fallen near the exit of the trap feel that it is not troublesome to drop the trap directly from the exit, so they continue to take the trap.
Dig a pit for the ants
In order to create negative memories for the ants, the researchers carefully laid out a bureau -
At a distance of 5 meters from the ant nest, they placed a feeder stuffed with biscuit crumbs. As ants travel from their nests to the feeder, they need to pass through a slender passage 15 cm above the ground that leads directly above the feeder.
Since the channel is above and does not touch the feeder, when the ants come down from the channel, after the feeder has picked up the food, they can only walk back to the nest from the sand-paved ground (there are references such as shrubs on the ground to locate). Because ants take the passage above the road surface when they come out of the nest, the return to the nest route will not be affected by the exit route.
During this ground journey back to the nest, the researchers set a trap 2 meters long, 10 centimeters wide and 10 centimeters deep. The inside of the trap is so smooth that the ants cannot climb up and can only exit from the exit in the direction of the nest. At the beginning of the experiment, the trap was hidden under the sand on the road surface, and the ants would not fall into it.
Schematic diagram of the experimental site | Author draws
The experiment was divided into four phases.
Phase 1:
The Australian desert ant (Melophorus bagoti) can freely travel back and forth between the feeder and the nest. The ants quickly formed their own routes, and they all passed by the location of the traps.
The trajectory of the ants is | References[1], author Sinicized
Stage 2:
Open the trap. When the ants first passed the trap, they were hit one after another, and after groping in the trap for a few minutes, they came out of the exit of the trap and continued to return to the nest. Due to the small exit of the trap, the first half of the trajectory of the ant's return to the nest can be seen to stop abruptly at the trap, and then uniformly depart from the trap exit and walk back to the nest.
Stage 3:
Continue to let the ants shuttle back and forth through the experimental field where the traps are opened. After 24 hours, it was found that some ants had formed a route around the trap.
The ants walked on the trail, and the ants that took the green trail successfully bypassed the trap | References[1], author Sinicized
Stage 4:
Close the trap. Of the 14 ants recorded, four formed a stable trajectory that bypassed the previous trap location.
The ants that follow the green trail form a stable, trap-riddle route | References[1], author Sinicized
"Cliff resemblance" is no accident
Only 4 ants bypassed the trap, could it be accidental?
The researchers switched to cataglyphis fortis and conducted experiments on a larger scale at a distance of 8 meters, and found that the results were similar.
To further rule out accidental factors, the researchers conducted a controlled experiment: in a controlled experiment that did not open the trap, all the ants' route back to the nest eventually passed through the location of the trap, and there was no random "bypassing the trap area" circuitous route.
Ants have limited vision, and the path integration ability does not allow the ant to see and recognize the trap in front of it before falling into the trap - so what makes the ant learn to "kill the ant from the cliff" after a series of pit trips?
If you look at the trajectory of individual ants from the time series, you can see that the ants gradually form a route around the trap and return to the nest in the process of "feeling the stones through the trap".
Ants can remember the path they have taken. When an ant falls into a trap, it places a "disgust" mark on the memory of a section of the route before it falls into the trap, and when it walks to the area in front of the trap again, the "disgust" mark activates, causing the ant to stop, begin to re-scan the surrounding environment, and continue to move forward after choosing a new direction.
That is, ants can associate the negative memory of falling traps with the memory of routes, and gradually "learn" to circumvent traps.
The red area indicates the area where the ant has an "aversive" memory, and the circled area is where the ant has a clear stop to scan the environment | References[1], author Sinicized
The ant in the picture below, in the negative memory of frequent pit drops on the first day, constantly learns and modifies the route. On the way back to the nest the next day, they successfully avoided the trap, and the number of stops to observe the environment gradually decreased.
As the number of times they passed the trap increased, the ants gradually learned to bypass the trap | References[1], author Sinicized
There are exceptions
The above experiments have shown that ants can learn to re-route around traps. But attentive students may ask, why only less than a third of the ants have successfully bypassed the trap, while some ants prefer to fall into the pit rather than take a detour?
First of all, learning requires enough training, and ants have only made less than ten round trips in 24 hours, which is not enough for some individuals to learn to get around traps and find a smooth way.
Second, the location of the trap will also affect the ant's final strategy. The researchers found that if the ants landed close to the exit of the trap when they dropped the trap, they would later be more inclined to return to the nest by the route they fell into the trap, rather than bypassing the trap, because it would return to the nest faster.
That said, to some extent, ants have the ability to calculate and choose routes that take less time.
If viewed from a more macroscopic perspective, the adaptive adjustment of ants to walking routes is actually an adaptation to the environment that has evolved over a long period of time.
Think about it, such a small creature as an ant, the brain capacity is not as large as a sesame seed, in order to better live on this blue planet, it is also trying to master some complex behaviors.
Source: Antoine Wystrach
bibliography:
[1] Wystrach et al., Rapid Aversive and Memory Trace Learning during Route Navigation in Desert Ants, Current Biology (2020), https://doi.org/10.1016/j.cub.2020.02.082
[2] Collett, T. S. (2019). Path integration: how details of the honeybee waggle dance and the foraging strategies of desert ants might help in understanding its mechanisms. The Journal of Experimental Biology, 222(11), jeb205187. https://doi.org/10.1242/jeb.205187
[3] https://www.iflscience.com/plants-and-animals/ants-can-learn-from-their-mistakes-to-avoid-traps/
[4] https://en.wikipedia.org
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