Physalaemus pustulosus also display optomotor responses under these conditions when the colours of the drum are filtered to mimic the reflectance spectrum of the male’s inflated vocal sac (M. Cummings, X. Bernal, C. Jennings, A. S. Rand & M. J. Ryan, unpublished data). These results indicate that the visual system of P. pustulosus can detect the vocal sac under the range of conditions in which males call in nature.