A video game developed for fish has provided new insight into how swimming in groups can protect them from predators.
The team from Princeton University developed its simulation of small prey to see how the risk of them being attacked changed depending on whether they were swimming alone, in a group or following other small prey fish.
The simulation was programmed so that the prey fish, which looked like red-coloured dots in the video, formed the different types of groups spontaneously — and the virtual prey were then projected onto a tank containing Bluegill sunfish (similar to the one pictured above) to see how they reacted.
"Effectively, the Bluegills were playing an immersive video game in which they hunted," Iain Couzin, a Princeton evolutionary biologist, said. And as with a typical video game, it was designed to get harder for the Bluegills as they progressed.
"In a similar way, our prey 'evolved' to the mode of hunting that the Bluegills exhibited, adapting better strategies that allowed them to evade hunting more effectively," Couzin said.
The results show that group formation itself can dissuade a predator, even if the prey — as in the simulation — are completely unaware of the danger, the researchers report.
Unsurprisingly, the study found that fish which swam in groups survived better than those that chose to swim alone. However it was also important for the groups of fish to balance closeness and co-ordinated movement.
Large groups of fish that didn't move much were more likely to fall victim to attacks in "high-risk" areas in which Bluegills preferentially attacked. Yet when groups of prey moved with co-ordination, they passed through these high-risk areas too quickly for each individual Bluegill to make its attack.
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