Co-divergence of mating traits and mate preferences can lead to behavioral isolation among lineages in early stages of speciation. However, mate preferences only limit gene flow when expressed as mate choice, and numerous factors might be more important than preferences in nature. In the extremely color polytypic strawberry poison frog (Oophaga pumilio), female mate preferences have co-diverged with color in most allopatric populations tested. Whether these lab-assayed preferences predict mating (gene flow) in the wild remains unclear. We observed courting pairs in a natural contact zone between red and blue lineages until oviposition or courtship termination. We found color-assortative mating in a disturbed habitat with high population density, but not in a secondary forest with lower density. Our results suggest color-assortative O. pumilio mate choice in the wild, but also mating patterns that do not match those predicted by lab-assayed preferences.