Cannibalism can accelerate larval growth in salamanders. Cannibal morph salamanders of the species Hynobius leechii come into contact with both siblings and non-siblings in vernal ponds and streams. Hynobiid salamanders have been observed cannibalizing during their developmental stages, and one study has shown that Hynobius leechii preferentially cannibalizes siblings. In this study, cannibal morph larvae were placed into a circular arena together with pairs of smaller larvae, one sibling and one non-sibling. Behavioral interactions among the larvae, filmed at night with infrared camera, were characterized on a scale of aggressiveness. Agonistic behaviors of cannibal morphs were compared based on their relatedness to the smaller larvae, while small larvae were scored on their interactions with cannibal morphs. Observations were repeated every 21 days for 3 months to determine whether aggressive behaviors changed over time. Preliminary results suggest that cannibalistic larvae behaved more aggressively toward siblings. Thus, cannibalistic morphs may actively discriminate among potential prey by their relatedness. We continue to study the functional significance of this discrimination.