Territorial male color predicts agonistic behavior of conspecifics in a color polymorphic species

Male cichlid fish, Astatotilapia burtoni, live in a lek-likesocial system in shore pools of Lake Tanganyika, Africa, asone of two distinct social phenotypes: territorial (T) malesthat comprise approximately 10–30% of the population andnonterritorial (NT) males that make up the rest. T males arebrightly colored either blue or yellow with chromatic body patternsand are larger, reproductively capable, and defend territoriescontaining a food resource used to entice females to spawn withthem. NT males are camouflage colored, smaller, have regressedgonads, and shoal with females. Importantly, males shift betweenthese social states depending on their success in aggressiveencounters. It is not known whether there is a difference betweenyellow and blue T morphs. Here we asked whether T males preferentiallydefend their territory against a male of the same or oppositecolor. T males observed in social groups had agonistic interactionspredominantly with neighboring T males of the opposite color,and yellow morphs initiated significantly more aggressive interactions.When agonistic preference was tested experimentally, T maleshad significantly more agonistic interactions toward males ofthe opposite color, and yellow T males became territorial inthe majority of those interactions. Taken together, these resultssuggest that male coloration is an important social signal amongneighboring T males in this species and support the hypothesisthat T males differentially direct agonistic behavior dependingon the color of neighboring males.