Temnothorax rugatulus. Credit: AntWiki.
Sometimes, when one ant starts moving, the whole colony may follow in mere seconds.
It’s a remarkably simple route to coordination, but it could help explain how large groups synchronize without anyone being in charge.
Essentially, a new model suggests that synchronized, pulsating bursts in ant nests can begin with a single worker, whose movements trigger a chain reaction through nearby nestmates. No leader, no quorum — just a colony poised to respond.
A Spark in the Nest
The key mention is that this is a modeling study, not a direct experimental proof. But the model reproduces important features of activity rhythms that biologists have observed in ants for decades.
Biologists first documented these rhythmic bursts more than 30 years ago in several ant species, including acorn ants such as Leptothorax acervorum and Temnothorax species. The behavior has puzzled researchers because it resembles patterns seen far beyond insect nests: neurons firing together, fireflies flashing in synchrony, fish schooling, even chemical reactions that flip suddenly from one state to another.
But researchers haven’t been able to figure out how that coordination emerges.
In the new study, researchers Michael Napoli, Simon Garnier, and Maurizio Porfiri developed a model that combines ants moving through a nest with changes in their behavioral states. Their goal was to determine what allows scattered individual activity to turn into synchronized colony-wide bursts.
In the model, each worker can occupy one of three states: active, inactive, or refractory. A refractory ant has recently been active and temporarily cannot be activated again.
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Illustration: ZME Science.
That brief refractory period is the key part. Without some mechanism allowing the colony to shut down, one burst could simply bleed into continuous activity. Instead, synchronized bursts emerge from a balance between two processes. The colony must be responsive enough for activity from an initial ant to spread through the group. But it must also deactivate thoroughly enough between bursts to reset the system.
“Activity bursts emerge as a balance between the responsiveness of the colony to the first ant that activates and the ability of the colony to completely deactivate before the onset of the next burst,” said Michael Napoli, a doctoral researcher at NYU.
Active ants move around the simulated nest and can activate nearby inactive ants. Those ants can then activate still more workers.
Under the right conditions, the process becomes a cascade.
No Boss Required
Perhaps the most striking result is how little the cascade appears to need at the beginning.
“In many collective systems, such cascades typically appear only if enough individuals are already active themselves—a quorum of sorts,” Simon Garnier, an NJIT professor of biological sciences, said in a statement. “The most surprising result is that a single ant is able to trigger an entire cascade of activity.”
The researchers call this ant a “first mover.” But it’s not a special individual or permanent leader.
“Synchronization does not depend on any specific individual; any ant can serve as the first mover,” Garnier told the American Physical Society.
The model showed that the colony enters a synchronized regime only after passing a critical threshold. Before that point, ants may move, meet, and prod one another, but activity dies out before it spreads far. After that point, the same kind of interaction can ripple across much of the group.
Physicists call such a sharp change a phase transition, and phase transitions appear in many places in nature. Water freezing is the familiar example: a small shift in temperature can change liquid into solid. In the ant model, a small change in density, movement speed, or sensing range can change scattered motion into coordinated bursts.
The swarm came as was foretold. Credit: Pexels
The model also points to speed as an important part of the phenomenon.
Ants do not need long conversations. They need enough brief contacts, made quickly enough, to pass activity from body to body before the signal fades. When ants moved too slowly or met too rarely in the simulation, no burst formed. When speed, density and interaction range crossed the threshold, motion spread rapidly.
“The timescale of the motion of individuals through the nest is faster than that of the burst, suggesting that ants operate in a high-speed interaction regime where new behaviors are near-instantaneously transferred through the nest,” Maurizio Porfiri, a senior author at NYU, said in a statement.
Put simply, information can move through the colony faster than the colony’s larger activity rhythm unfolds.
The finding matters because it could help explain how colonies react quickly to threats or environmental changes. Synchronized reactions are useful, but speed can carry a cost. If the first ant reacts to a false cue, the colony could burn energy on a useless mobilization.
The implications could also extend outside biology. Robot swarms, autonomous vehicles, and distributed sensor networks all face a similar problem: how to coordinate many agents without central control. Ants may offer a lesson in how a group can move quickly, reset, and prepare for the next signal.
For now, it’s a convincing model, but still just a model Napoli said that experiments are now being analyzed to test the model against real colony data.
The accepted paper is listed in PRX Life.