Swimming in schools allows fish to detect threats more easily, and new research -- in which fish were placed in something of a video game -- suggests schooling behavior actively deters predators.
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PROBLEM: It's thought that shoaling or schooling behavior among fish confers various biological benefits: the proliferation of targets reduces any single fish's risk of being eaten by predators, and it increases the chances of finding a suitable mate. Less well understood, however, is the relationship between a group's behavior style and the likelihood of it coming under attack. Aren't they also making themselves a more conspicuous, easier target?
METHODOLOGY: As demonstrated in the video below, researchers projected small dots in various groupings -- from one to five or more -- onto a fish tank to simulate prey. The dots were pre-programmed to link up with other dots, to swim with them in the same direction, or to ignore other dots completely. Researchers then introduced a predatory fish into the tank and watched how it behaved according to the way the dots were programmed.
RESULTS: Having established an "immersive video game" for the hunting fish, the scientists observed that large groups of dots moving quickly through the fish's hunting grounds came under attack far less frequently than either small groups of dots, and even large groups of dots that moved slowly. Dots that learned to balance their attraction to other dots with a desire to swim in the same direction as their companions fared the best.
CONCLUSION: Dots that swam in a group had a better "survival" rate than dots swimming alone. Grouped dots that swam continuously in a coordinated fashion fared even better. Faced with a choice of targets, the fish preferred to go after isolated and uncoordinated prey.
IMPLICATION: Schooling behavior not only provides a passive "safety in numbers" effect, but it actively deters predators.
SOURCE: The full study, "Predatory Fish Select for Coordinated Collective Motion in Virtual Prey," is published in the journal Science.
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