Performance Consequences of a Trophic Polymorphism: Feeding Behavior in Typical and Cannibal Phenotypes of Ambystoma tigrinum

Abstract

Aquatic feeding behavior, prey capture performance, and morphological aspects of the feeding mechanism were compared in typical and cannibal phenotypes of Ambystoma tigrinum melanostictum to test the hypothesis that the trophic polymorphism affords a performance advantage in feeding. Similar-sized salamanders of the two phenotypes differed morphologically in size of the vomerine tooth patches and head width but not in size of the gape or mass of the hyoid retractor muscles used in suction feeding. Suction feeding and prey handling performance did not differ between the two morphs feeding on live guppies or small conspecific salamanders. However, differences were found in willingness to feed on conspecifics and prey handling performance when feeding on larger salamander larvae. Thus, cannibal morphs possess a significant performance advantage only during predation on large conspecifics. The performance advantage on large prey appears to be a consequence of greater prey handling ability facilitated by the increased size of the vomerine tooth patches.