Scientists have observed neon tetra fish queuing up when exiting through a narrow opening, according to a study in the journal Scientific Reports.

In the study, Aurélie Dupont, a biological physicist in the Laboratoire Interdisciplinaire de Physique at University Grenoble Alpes, and her team set up two fish tanks connected to each other by a narrow opening. The diameter of the passageway varied from 1.5 to 4 centimeters.

Then, the fish were placed into one of the tanks and a fish net was used to "herd" the fish to the opening, so that they would swim into the other tank.

The researchers observed that the fish, which measured from half a centimeter to three centimeters, demonstrated different evacuation rates, but generally maintained a steady pace, except for the last few fish in each group, which exited more slowly.

No physical contact, collision or conflict was observed among the evacuating fish as they gathered around the openings.

This orderly behavior suggests that neon tetras wait or queue before evacuating, maintaining a preferred social distance.

Such behavior resemble those observed in ants but are in stark contrast to tendencies seen in sheep herds and human crowds, where clogging often occurs during evacuations.

The study's authors suggest that these fish behaviors may mirror those of wild neon tetras as they navigate between rocks in rivers.

They also believe that the findings have the potential to be considered in the development of swarm robots and for enhancing traffic management for autonomous cars and human gatherings.