This study examines changes in the frequency/abundance of prey selection among five size classes of 183 Ambystoma jeffersonianum (Jefferson Salamanders) within a natural, unmanipulated environment. Significant differences were found in prey selection among size classes in vertebrate and macroinvertebrate (specifically coleopteran and dipteran) prey groups, but not microinvertebrates. Predator-size thresholds were noted as diet shifted from predominantly microinvertebrates to increasingly larger macroinvertebrates to the final dietary selection of other vertebrates. This study augments the catalogue of ingested Ambystoma prey and re-examines the nature of ontogenous dietary selection.