Real birds pecking virtual moths have shown how camouflage probably evolves. The computerized prey adapted to blend into their background, and developed a wide range of different markings.
University of Nebraska biologists made virtual moths. A set of computer instructions representing an electronic genome determined their wing patterns. The researchers trained captive blue jays to hunt the moths. Pecking at an on-screen moth earned a jay a food pellet. After each round, the hardest-to-find moths bred with each other and mixed their digital genes, with a little bit of random mutation thrown in. After 100 generations, the moths were about 30% harder to find, and their pattern repertoire had nearly doubled.

The result is also some of the best evidence that animals search for images, and that something is easier to find if you know what it looks like.

The computer experiment also demonstrated that rarity can compensate for camouflage. Virtual moths evolved to blend into the background more quickly in control experiments when rarity was not a factor.