The function of aggression in the swordtail, Xiphophorus helleri: resource defence
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Competition for mating opportunities may involve exclusion of intrasexual competitors (direct) or defending resources necessary to attract mates (indirect). Male swordtails (Xiphophorus helleri) engage in direct competition. Moreover in natural populations they defend a home range. This study aimed to test whether this home range defence is a form of food resource defence, which may therefore have a female attraction function. Male swordtails did defend a food resource and showed increased aggression in the presence of both food and females. However, food resource defence decreased when females were present, suggesting that both food and females are treated as defendable resources.
KeywordsAggression Resource defence Dominance Home range Male size
We thank several anonymous referees for their comments on this manuscript. This work was funded by the Rhodes University Postdoctoral Fellowship (KM).
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