The evolution of mimicry is one of the most powerful examples of evolution driven by natural selection; however it is rare in non-insect taxa and thus is understudied. Ranitomeya imitator underwent a 'mimetic radiation' and now mimics three congeneric model species (R. fantastica, R. summersi, and two morphs of R. variabilis), creating geographically distinct populations of the species, including four allopatric mimetic morphs. These complexes are thought to represent a case of Müllerian mimicry, but no prior empirical studies on learned avoidance by predators support this claim. In this study we used young chickens (Gallus domesticus) as naïve predators to determine if a co-mimetic morph of R. imitator and R. variabilis contribute to reciprocal learned avoidance by predators-a key component of Müllerian mimicry. Chickens exposed to either stimulus species demonstrated reciprocal learned avoidance; thus our results indicate that this complex functions as a Müllerian mimicry system. This study provides novel empirical evidence supporting predictions of the Müllerian mimicry hypothesis in anurans. Our study shows no difference between learned avoidance in stimuli frogs and a 'novel' morph of R. imitator that differed in both color and pattern, indicating that learned avoidance by predators may be generalized in this system. Generalized learning provides a plausible mechanism for the maintenance of both polytypic mimicry and the maintenance of intrapopulation phenotypic heterogeneity. © 2013 Springer Science+Business Media Dordrecht.