That’s what you get for not being shellfish.
Every apocalypse or supervillain movie features a stampede scene, where selfish humans push through one another to ensure their own survival – only to make everything worse. One very sensible species of fish forms queues to avoid exactly this issue, according to a new study.
When evacuating through narrow spaces, schools of neon tetra fish (Paracheirodon innesi) queue so that they don’t collide or clog up the line.
“We interpret this behaviour as respecting the social rules even in an emergency situation,” Aurélie Dupont and Philippe Peyla, co-authors of the study published in Scientific Reports, told BBC Science Focus. “It seems that humans, like sheep, tend to quickly forget about social rules when they encounter a stressful situation, and rather adopt a selfish behaviour.”
In the wild, neon tetra fish have to navigate around rocks in the rivers they swim along. To test how they do this when moving in large groups, a team of scientists from the University Grenoble Alpes, France, put the fish in a tank with narrow openings leading to other compartments.
These openings ranged in size from 1.5 to 4cm: not much bigger than the size of the fish themselves, which are 3cm long and 0.5cm wide.
The scientists then moved a fishing net through the tank and observed groups of 30 neon tetra fish as they evacuated through these openings.
The team were surprised to see that the fish gathered around the openings before passing through them – managing to avoid physical contact and clogging so that they could pass through at a constant rate.
The study marks the first time an experiment on crowd movements has focused on group evacuations in water. Previous observations have focused on animals that walk on 2D, solid surfaces.
Crowd movements occur across many species and at different scales – but with varying degrees of success. The scientists who conducted this study note that the evacuation behaviour of neon tetra fish is similar to behaviour in ants, but a far cry from the clogged-up chaos of evacuation by sheep herds and human crowds. Clogging decreases the efficiency of an evacuation.
The team hopes that these findings might inform the development of swarm robots and better traffic controls – for both human and autonomous cars.
About our experts
Aurélie Dupont is a biological physicist in the Laboratoire Interdisciplinaire de Physique at University Grenoble Alpes in France. Her research has been published in Scientific Reports, Nature Communications, and Physical Review.
Philippe Peyla is deputy director of Les Houches School of Physics at University Grenoble Alpes. His research has been published in the Journal of Fluid Mechanics, Solid State Electronics, and Physical Review Fluids.
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