The Relationship between Resource Competition, Risk, and Aggression in a Tropical Territorial Lizard

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Abstract
A model is proposed which relates intraspecific aggression to competition for resources and risk from aggressive encounters. Field studies of the lizard Anolis aeneus indicate that ♀ ♀ probably compete for food, ♂ ♂ for mates. Evidence includes sexual dimorphism in spacing patterns and synonymy of ♂ territoriality and mate defense through a short—term ♀ pair bond. Competition for food between ♀ ♀ of different sizes is presumed to be proportional to the overlap in prey size distributions between those ♀ ♀; competition for mates by ♂ ♂ should be equally strong among all mature ♂ ♂. By subtracting size ratio dependent risk functions from competition functions it is possible to predict aggression between animals of specified sizes. Experimental field studies tethered intruders indicate that size specific aggression in ♀ ♀ conforms closely to that predicted from the food competition model, while aggression in ♂ ♂ conforms to the mate competition model.