No individual recolours itself to match the background. What moves is the colour distribution of the whole population, because conspicuous individuals get eaten more often and well-matched ones leave more offspring. The darker the background, the further the mean trait creeps after it generation by generation, and the harder the selection, the narrower the diversity left behind. Industrial melanism in the peppered moth is the classic case of that shift, while with no predators at all the distribution simply wanders by drift.
No individual recolours itself to match the background. What moves is the colour distribution of the whole population, because conspicuous individuals get eaten more often and well-matched ones leave more offspring. The darker the background, the further the mean trait creeps after it generation by generation, and the harder the selection, the narrower the diversity left behind. Industrial melanism in the peppered moth is the classic case of that shift, while with no predators at all the distribution simply wanders by drift.
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