Aposematic coloration of prey enhances memory retention in an agamid lizard

Toxic or noxious prey often signal their unpalatability through aposematic coloration, and the evolution of aposematism has become a model system in evolutionary behaviour. Aposematic colours are not only easily recognized by predators, but, for many predators, aposematism enhances learning and memory retention. In this study, we used a visually oriented, insectivorous agamid lizard, Diploderma swinhonis, to test whether aposematic coloration enhances lizards’ ability to detect and remember distasteful prey. We exposed lizards to quinine-flavoured crickets, Gryllus bimaculatus, that were dyed with colours generally regarded as aposematic (red) and nonaposematic (green). After a single exposure, lizards readily learned to reject both red and green crickets, but in subsequent trials they were more hesitant to attack red than green ones. However, the lizards remembered both types of prey for up to 60 days and showed a similarly high rate of generalizing that aversion from coloured to noncoloured crickets. Our results demonstrate that visually hunting lizards exhibit nuanced patterns of learning and memory in foraging tasks and make ideal subjects for experimental work on aposematism.