SUBORDINATE SWORDTAIL MALES ESCALATE FASTER THAN DOMINANTS - A FAILURE OF THE SOCIAL CONDITIONING PRINCIPLE

In previous studies we have shown that subordinate swordtail males (Xi phophorus helleri) direct more bites to their mirror image than domina nts and, in confrontations with strange dominant males, approach the o pponent more often during the pre-escalation period of fights. Consequ ently, we predicted that fights between two omega-males should escalat e faster than fights between two alpha-males. Indeed, in omega-omega f ights pre-escalation periods were shorter and biting rates were higher than in alpha-alpha fights before the fights escalated from the first retaliation bite onward. Another new observation was that in omega-al pha confrontations the first bite in the pre-escalation period was exe cuted more often by the omega-male and there was also a tendency to bi te more compared to the alpha-male in that stage of the encounters. We conclude that subordinate males escalate faster and fight more offens ively prior to escalation than do dominant males. The results cannot b e explained by the ''social conditioning principle.'' On the ultimate level moderate costs of losing and high benefits of winning a fight, c onstraints on continued growth after maturing, short life-expectancy, and habitat saturation are probably factors promoting the offensive ta ctics of subordinate males.