Androgen and Corticoid Levels in Blood and Body Extracts of High‐ and Low‐ranking Swordtail Males (Xiphophorus helleri) before and after Social Isolation

and Summary The two highest- and the two lowest-ranking swordtail males were determined by the criterion of number of attacks directed at and received from every other male in their breeding tanks. The events were recorded until 50 bites were given (high-ranking males) or received (low-ranking males). 40 high- and 40 low-ranking males were bled either after being socially isolates for 4 weeks or after reaching the target number. Androgen and corticoid concentrations both in their blood and their body extracts were measured by means of radioimmunoassay. Although the agonistic behaviour patterns and social experience of high- and low-ranking males were totally different, the baseline hormonal states of the animals were indistinguishable both in body extracts and blood. Isolation led to decreased blood androgen and corticoid levels in high- and low-ranking males. In the body extracts, only the corticoids were reduced. A significant correlation between blood and tissue concentrations was found only in the case of corticoids. I would suggest that the contradictory findings in the literature dealing with the relationship between hormones and dominance result from differences in experimental procedure.