Social Familiarity and Nip Dominance in Male Swordtails (Xiphophorus Helleri) and Platys (Xiphophorus Maculatus)

Abstract

Male swordtails and platys ( ns =12) were tested for nip dominance among familiar (tankmate) and unfamiliar (nontankmate) con-specific pairs in four round robin contests conducted at weekly intervals. Stable dominance relationships were found for both species, with less aggression manifested between familiar swordtail pairs, and to a lesser extent, between familiar platy pairs, than between nonfamiliar pairs. Significant correlations between physical size and dominance status were also found for both species.