CogprintsRelation between dominance rank, prior agonistic intensity and subsequent aggressive levels in winners and losers of dyads of male Green swordtail fish (Xiphophorus helleri)ClaudeGouletauthorJacques P.BeaugrandauthorAggressive scores obtained in a mirror test 1h before an encounter were found to be a good predictor of victory in male Xiphophorus dyads showing less than 5% size differences. Out of 36 dyad members showing higher aggressive scores at pre-test, 28 obtained victory in the subsequent encounter. It was found that future winners were more aggressive than future losers to their own image in mirror tests before their encounter. Initial individual aggressive levels in mirror tests were also found to be a function of the rank the individuals occupied in their home hierarchies. The higher the rank, the higher was the individual aggressive level as measured by mirror pre-tests, as well as by post-tests. This relationship applied to future winners, as well as to future losers. The level of aggression reached during agonistic encounter was not a function of the social ranks the opponents occupied in their home hierarchies. Males in dyads composed of two omegas fought as fiercely as males in dyads of two alphas or two betas. No significant relationship was noted between the initial individual aggressive scores at mirror pre-test and the levels of aggression reached during encounters. We found in winners the existence of a significant correlation between the aggressive level they reached during agonistic encounter and a subsequent increase in aggressive levels at mirror tests 1h and 24h after victory. The more intense the agonistic encounter, the more important the subsequent increase in aggressive level in winners; an increase which was still detectable 24h after victory. However, prior alpha winners were apparently not as sensitive as prior betas and prior omegas to the aggressive level reached during the encounter since their mirror scores obtained after victory did not change when compared to their baseline at pre-test. After defeat, losers did not show any significant change in aggressive scores in mirror tests. Moreover, it was found that encounters in which a 1h resident met an intruder were in general less aggressive than encounters between two intruders. Experiential effects are discussed as instances of learning and generalisation. Animal BehaviorEthology2001-11Preprint

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