It's a curious scene in nature: When a lion rushes a pack of gazelles, the animals clump together as they run away, rather than scatter in 50 different directions. Scientists have long suspected that the clumps somehow confuse the predator—and now they have new proof. A team of biologists and computer scientists devised computer simulations that allowed predators and prey to evolve in response to each other. At first, the hunter (red) and the hunted (white) moved about randomly, with the hunter occasionally making a kill and the prey occasionally getting away. But over successive generations, the prey clumped more and more in response to the predator, until the predator's success rate became quite low—similar to what is seen in the wild (compare the predator's ability to pick off two prey—white dots disappearing—in the early seconds of the video versus at the end), the team reports online this week in the Journal of the Royal Society Interface. This only happened, however, when a predator was programmed to be confused by such clumping. If the predator was not confused, the prey never evolved to clump, and high numbers continued to "die." So whether it's the real world or the virtual one, it pays to stick together when predators pounce.
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