Modeling Dominance: The Influence of Size, Coloration, and Experience on Dominance Relations in Tree Lizards (Urosaurus ornatus)

Abstract

Two populations of tree lizards (Urosaurus ornatus) that differ in morphological and social traits were used in a comparative study examining the relative influence of several variable characteristics on dominance relations. Adult males from the Aguirre Spring (AS) population exhibit monomorphic throat coloration, whereas Dofia Ana (DA) males are polymorphic. AS males are, in certain respects, more aggressive than DA males. Pairwise dominance contests were staged to assess relative contributions of size, social experience, and throat coloration in determining dominance outcome. Although the relative size of individuals has usually been regarded as a primary predictor of dominance, recent studies have shown that a disparity in color or experience can serve to override size differences between contestants. Data for size, recent dominance experience, and throat coloration were entered into logistic regression programs to generate models that were both predictive and explanatory. These models indicated effects of size, experience, and coloration in both populations. Throat coloration was a relatively stronger predictor of dominance outcome in males from the polymorphic (DA) population, whereas previous dominance experience was more important in AS males.