 Salamanders are opportunistic predators . They are generally not restricted to specific foods , but feed on almost any organism of a reasonable size . Large species such as the Japanese giant salamander ( Andrias japonicus ) eat crabs , fish , small mammals , amphibians , and aquatic insects . In a study of smaller dusky salamanders ( Desmognathus ) in the Appalachian Mountains , their diet included earthworms , flies , beetles , beetle larvae , leafhoppers , springtails , moths , spiders , grasshoppers , and mites . Cannibalism sometimes takes place , especially when resources are short or time is limited . Tiger salamander tadpoles in ephemeral pools sometimes resort to eating each other , and are seemingly able to target unrelated individuals . Adult blackbelly salamanders ( Desmognathus <unk> ) prey on adults and young of other species of salamanders , while their larvae sometimes cannibalise smaller larvae . 
