One of the craziest animal adaptations is the “ant death spiral” or “ant mill.” This happens when army ants get lost in a pheromone track. This event is a strange natural occurrence that is a unique hiccup in evolutionary biology. “Follow something blindly, and you’ll end up paying the price.” This saying could not be more true for army ants. Unfortunately, the little critters may end up paying the ultimate price simply because their instincts lead them to their demise. So what is the “ant death spiral”? And why does it happen? Keep reading to find out!
What Is The “Death Spiral”?
A “death spiral” is a strange natural phenomenon in which a colony of ants essentially commits suicide by following each other in an endless circle until they die of exhaustion. Army ants are blind, so they follow the pheromones of a single lead ant. If this ant gets off track or ends up breaking the formation, the ants may end up in this endless “death spiral.”
Why Does The “Death Spiral” Occur?
Army ants work very well as a group. In fact, an individual ant would not likely survive on its own, but as a collective effort, the ants feed the entire colony and can build intricate tunnel systems. Army ants are blind, but they can find food and move freely by following each other’s scent. Their ability to work so well together and follow each other in an almost robotic way is thanks to the pheromones the ants produce that attract other ants to follow them. These pheromones produce an almost “hive mind” community. The ants blindly follow each other to find food to feed the queen and the colony. If the lead ant encounters an obstacle such as a fallen log, a wall, or a predator, it will have to turn around or find another route, sometimes this change in direction will confuse the other ants in line, and the ants will start circling, frantically following each others scent. The lead ant will then begin to follow another ant’s scent, and the entire colony will spiral endlessly.
Which Kind Of Ants Do The “Death Spiral”?
There’s a specific species of ants that do this bizarre spiral. There are several species of army ants across North and South America, but all of them have at least one thing in common: the “death spiral.” Army ants or Labidus praedator are entirely blind and don’t live permanently in ant hills like most other ants. Instead, they are always on the move, following the leader, in their massive groups, searching for food. Each colony may be as big as 1,000,000, with large groups from each colony going out to forage for food at one time.
How Was The “Death Spiral” Discovered?
Ant milling was discovered in 1936 when scientist T.C. Schneirla came across hundreds of ants spiraling endlessly. Scientists were baffled by this behavior, and it seriously confused evolutionary biologists as it seemed to contradict Darwin’s “survival of the fittest” theory. Since then, many entomologists (insect experts) and evolutionary biologists have studied army ants to learn more about this behavior and the herd mentality that comes from their potent pheromones.
Why Didn’t They Evolve?
Army ants have been around for millions of years, so why didn’t they evolve out of this adaptation that is clearly a glitch in the evolutionary chain? One scientist stated: “You’d think spiral-induced mortality would be selected against, that ants would have evolved a counter-measure to such obviously maladaptive behavior. ‘Hey, here’s an idea! How about let’s stop circling?’” Scientists still haven’t determined why these ants have not grown out of this behavior. But, the general hypothesis is that the army ant population is not really affected much when it loses 1,000 or even 5,000 ants to an ant “death spiral.” Each colony can have upwards of 1,000,000 individuals, so if anything, the “death spiral” functions as population control. This adaptation has done a lot of good for army ants. They function very differently than the standard insect, and their massive colonies have a behavior that is unlike anything else in nature. But the adaptation is also a double-edged sword that can lead to the eternal “death spiral.”
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