Scientists studying the cooperative behavior of Longhorn Crazy Ants (Paratrechina longicornis) witnessed individual colony members performing several seemingly impossible feats of swarm intelligence, such as anticipating and clearing potential obstructions for other members transporting food back to the nest.
The team that witnessed the unexpected behavior initially assumed individual Longhorn Crazy Ants were somehow anticipating others’ needs and acting accordingly. However, laboratory experiments confirmed the ants were instead working collectively like neurons in the human brain to perform advanced planning tasks with a level of forethought well beyond any individual ant’s limited brain capacity.
Witnessing Longhorn Crazy Ants Using Swarm Intelligence
Longhorn Crazy Ants received their name because whenever they discover food, they touch their abdomens to the ground every 0.2 seconds as they run. This staccato stride may appear ‘crazy,’ but the ants are actually depositing small pheromone markers on the ground with each abdomen drop. These chemical signals allow the ants to communicate with the rest of the colony by marking routes to and from food sources.
When studying this behavior in the ant’s natural setting, Dr. Ofer Feinerman, a Weizmann Institute of Science professor, Dr. Ehud Fonio, a Weizmann Institute research fellow, and colleagues witnessed something unexpected. As one team of ants was transporting prey back to the nest, other individual ants appeared to anticipate the team’s path and remove tiny pebbles that could hinder the transport ahead of time. Based on the individual ant’s poppy seed-sized brain, this level of forethought seemed impossible, leaving the scientists scratching their heads.
“When we first saw ants clearing small obstacles ahead of the moving load, we were in awe,” Feinerman said. “It appeared as if these tiny creatures understand the difficulties that lie ahead and try to help their friends in advance.”
Curious how the brains of Longhorn Crazy Ants, which typically contain 250 thousand to 1 million neurons (compared to the 86 billion in a human brain) could accomplish such impressive forethought, the Weizmann Institute-led team decided to replicate the conditions in a laboratory setting. If successful, they hoped to explain how ant colonies appeared to exhibit a form of swarm intelligence beyond the capacity of any individual ant’s brain.
Lab Experiments Reveal Something Even More Awe-Inspiring
The team began by substituting natural pebbles with plastic beads 1.5 millimeters in diameter, half the typical Longhorn Crazy Ant’s body. Instead of living prey, the team used pellets of cat food, which the ants prefer. After running 83 experiments, the team witnessed several instances of the crazy ant’s ‘supercolony’ displaying this seemingly premeditated obstacle-clearing behavior.
According to the team’s published study, most events involved single ants moving plastic beads located an average of 40mm from the transported food in the colony nest’s direction. The ants typically moved the obstacles up to 50mm from the anticipated path with their mandibles before being dropped. While workloads varied, the team said that one particularly industrious ant cleared a “record-breaking” 64 beads in succession.
One notable exception to the behavior occurred when the food pellet was in crumbs rather than whole. In those instances, individual ants carried the crumbs by themselves and simply walked around any obstacles, rather than the collective efforts needed to transport larger prey.
Perhaps the most unexpected realization came from the mechanics of how the ants were working together to accomplish all aspects of food transport, including the obstacle-clearing behavior. For example, ants that cleared the obstacles didn’t need direct contact with the food beforehand. Instead, their behavior was prompted by ‘forager’ ants who had previously marked the path. Even a single pheromone marker indicating a food source was enough for a worker ant to begin clearing the path back to the nest, one obstacle at a time.
Dr Danielle Mersch, formerly a postdoctoral researcher at the same institute, says that, taken together, these collective behaviors show their initial evaluation was wrong. Instead of any individual ant being smart enough to anticipate the future, the decision to clear a path happened “at the colony level.”
“Each ant follows simple cues – like fresh scent marks left by others – without needing to understand the bigger picture, yet together they create a smart, goal-directed outcome,” Mersch explained.
Dr. Feinerman believes the overriding lesson from their experiments is how individual ants’ brains worked together like a larger collective brain swarm intelligence to accomplish a task beyond the capabilities of one individual. Feinerman likened the situation to that of a human brain, where “from the activity of the relatively simple computational units, namely neurons, some high cognition capabilities miraculously emerge.”
“Humans think ahead by imagining future events in their minds; ants don’t do that,” the professor explained. “But by interacting through chemical signals and shared actions, ant colonies can behave in surprisingly smart ways – achieving tasks that look planned, even though no single ant is doing the planning.”
“We find this to be even more awe-inspiring than our initial guess,” he added.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.