Résumé
The convergent evolution of warning signals in unpalatable species, known as Müllerian mimicry, has been observed in a wide variety of taxonomic groups. This form of mimicry is generally thought to have arisen as a consequence of local frequency-dependent selection imposed by sampling predators. However despite clear evidence for local selection against rare warning signals, there appears an almost embarrassing amount of polymorphism in natural warning colours, both within and among populations. Since the model of predator cognition widely invoked to explain Müllerian mimicry (Müller's "fixed nk" model) is highly simplified and has not been empirically supported, here we explore the dynamical consequences of the optimal strategy for sampling unfamiliar prey. This strategy, based on a classical explorationexploitation trade-off, not only allows for a variable number of prey sampled, but also accounts for predator neophobia under some conditions. In contrast to Müller's "fixed nk" sampling rule, the optimal sampling strategy is capable of generating a variety of dynamical outcomes, including mimicry but also regional and local polymorphism. Moreover, the heterogeneity of predator behaviour across space and time that a more nuanced foraging strategy allows, can even further facilitate the emergence of both local and regional polymorphism in prey warning colour.