Ant Death Spiral: Why Do Ants Walk In Circles?
The ant death spiral is a phenomenon wherein a group of ants follows each other in an endless circle. They do this until they somehow manage to break out or unfortunately die of exhaustion. The ant death spiral is otherwise known as the ant mill.
In this article, we’ll learn more about this bizarre phenomenon as we discuss the following:
- The discovery of the ant mill
- How the ant death spiral occurs
- If ants can escape the death spiral
- Which ants do the ant death spiral
How Was the Ant Death Spiral Discovered?
The ant death spiral was discovered by the scientist W.M Wheeler. He observed the phenomenon as he was studying the ant species E. schmitti. [1]
He kept a colony of these ants inside a jar where they walked up and down in files. When he removed the lid, the ants went out and made their way down to the circular base of the jar.
There they started, as Wheeler put it, following each other like sheep. The ants had no idea that they were walking the same path over and over. This went on for 46 hours until a few members broke out and caused the other ants to also spread out.
Wheeler considered this to be a limitation of instinct. These ants were blind and heavily reliant on the sense of their antennae. They kept following the trail, failing to realize that they were not making any progress.
How Do Ant Death Spirals Occur?
As Wheeler said, this is a limitation of instinct. Many visually impaired ants rely heavily on their sense of smell. Army ants, for example, are blind. They use pheromones and their antennae to communicate and navigate.
When army ants forage, the first ants in line leave scent trails made with pheromones. The rest of the group detects these pheromones and follows their lead.
As they do, they reinforce these trails by depositing pheromones of their own. This communicates to the group the direction that they are going. It ensures that the whole foraging group can navigate their way to the destination.
When this system works, it allows for large and efficient foraging groups. However, the problem starts when these ants fail to follow the main trail and get lost. This can be due to external factors like random obstacles, predators, or sudden rain.
As they try to find the trail, they may somehow loop back to their own scent while leading those behind them. When this happens, the ant death spiral occurs.
Can Ants Escape The Death Spiral?
It’s unlikely for ants to escape the death spiral, but it isn’t impossible. Much like how they start, external triggers such as strong winds or rain could break the loop. Even then though, the possibility of escape remains low.
A study involving the species E. praedator shows how rain fails to stop the death spiral. In this study, the rain was shown to make some ants stop in their tracks as they hesitated to enter wet areas. However, they were still forced to move on forward due to other ants pushing them from behind. [2]
In the end, the rain only shifted the orientation of the spiral. The rotation never stopped.
As for escaping the spiral on their own, it’s almost impossible. The same study notes that at one point some ants were able to escape. However, they eventually got caught back in the spiral as they wandered around its outer section.
With all that said, the fact that they can sometimes break out does mean that there is at least a chance of escape. Again, unlikely but not impossible.
Which Ants Do the Ant Death Spiral?
Ant death spirals typically occur with army ants. These ants include over 200 species of predatory ants coming from different genera. They include the aforementioned species E. schmitti and E. predator.
See this article to learn more about army ants.
Related Questions
What is the Largest Ant Death Spiral?
The largest observed ant death spiral was 1,200 (370m) ft in circumference. Moving just about 3 inches per second, it took each ant around 2 and a half hours to finish a revolution. [3]
Summary
To summarize, the ant death spiral is otherwise known as the ant mill. It’s a strange and unfortunate bug in the generally effective pheromone system of ants.
When that system fails to work, ants can start following each other in a never-ending loop. Barring some sort of interruption, they often die of exhaustion.
