1. With only a few exceptions, the potential contribution of heterospecific prey to the evolution of cannibalism and accompanying morphologies in amphibians and other taxa is unknown. In this study we tested the role of invertebrate and vertebrate prey in controlling variation in frequencies of a non-cannibal and an environmentally cued cannibal morph among populations of the Arizona tiger salamander, Ambystoma tigrinum nebulosum. 2. In parts of its range, A. t. nebulosum is syntopic with larvae of the chorus frog, Pseudacris triseriata. Our field measurements revealed a significant positive correlation between the frequency of cannibal morphs in larval tiger salamanders and density of chorus frog tadpoles. Cannibal frequency did not correlate significantly with larval salamander density, although frequency of cannibals varies positively with conspecific density in the laboratory