Optimal defensive coloration strategies during the growth period of prey.

Defensive coloration that reduces the risk of predation is considered to be widespread in animals. Many closely related species adopt differing coloration strategies during the life cycle, including crypsis, conspicuousness, and ontogenic change between the two coloration types. Here, we use a dynamic state-dependent approach to use ecological and intrinsic factors to predict the proportion of the developmental period of immature animals that should be spent as cryptic or conspicuous, and when conspicuous coloration should be reliably associated with investment in defenses. The model predicts that animals should change color more than once during development only in specific circumstances. In contrast, change from crypsis to conspicuous can occur over a range of conditions related to the frequency of detection by predators, but may also depend on the opportunity costs of crypsis and the effect of size on the deterrent effect of conspicuous coloration. We also report the results of a survey of coloration strategies in lepidopteron larvae, and note a qualitative agreement with the predictions of our model in the relationship between body size and coloration strategy. Our results provide explanations for several widespread antipredator coloration phenomena in prey animals, and provide a comprehensive predictive framework for the types of coloration strategies that are employed in nature.