A diverse array of animals has evolved the ability to use tools (e.g., primates, parrots, octopus, crabs, and wasps), but the factors leading to tool use evolution are poorly understood. Fishes could provide insight into these factors via comparison of differences between tool-using and non-tool-using species. Anvil use is one example of tool use by fish: the fish holds a hard-shelled prey item in its mouth and strikes it onto a hard surface (anvil)...
