An Experimental Model of Aggressive Dominance In

An experimental model was constructed using seven postulates derived from the experimental results of Zayan (1974, 1975a,b,c, 1976). The model specifies the relative importance of several asymmetries in predicting aggressive dominance in Xiphophorus helleri. These asymmetries concern differences between opponents with respect to: prior residence in the tested area (versus intrusion); immediate social experiences of dominance or submission; social isolation; individual familiarity and recognition. The predictions of the general model were checked experimentally and confirmed; a multiple orthogonal regression accounted for about 97% of the variance in our experimental results. The basic experimental results serving as postulates were confirmed and could be generalized; a new synthetic and predictive model was formulated concerning the determinants of aggressive dominance in Xiphophorus males. The following empirical generalisations were either confirmed or disclosed by the present study of opponents showing very small size differences: G1: The dominance propensity is significantly higher in resident individuals than in intruders. G2: The dominance propensity is significantly higher in previously dominant individuals than in previously submissive ones. G2 holds true for dyadic encounters between acquainted as well as between unacquainted pair-members. G3: The dominance propensity is similar in previously dominant individuals and in previously isolated ones. G4: The dominance propensity is significantly higher in previously isolated individuals than in previously submissive ones. G5: G2 overrides G1 in both acquainted and unacquainted opponents. In general it was found that recent agonistic experience (victory or defeat) was much more important to explain future issues than familiarity with the meeting place. However, negative effects of recent defeat appeared diminished when the prior loser encountered on familiar ground a prior dominant or isolated but unacquainted opponent. Reprint requests should be addressed to the first author. E-mail: [email protected]