When should males lek? Insights from a dynamic state variable model

Abstract

A central focus in the study of lek evolution is to understand the clustering of male mating territories. Lekking males typically defend small clumped territories and experience intense competition associated with dense aggregations. We used dynamic state variable modeling to evaluate three alternative selective pressures proposed to explain the evolution of lekking. These are female mating bias for large clusters, reduction in predation risk in large clusters, and male harassment of estrous females. We modeled male mating decisions during a single breeding season using a lekking ungulate as a model system. Males could choose from eight alternative tactics that included a nonreproductive tactic, territorial tactics ranging from low to high clustering, and the option to join a mixed-sex herd. The model predicted a state- and time-dependent strategy that maximizes mating success over the course of the season. We then simulated a population of 100 males that used the optimal strategy and calculated the proportion of the population that adopted each tactic. Our model generated unique predictions for the three selective pressures we considered. Female mating bias, when nonlinearly related to cluster size, had the greatest potential to generate large clusters of territorial males, whereas predation risk and harassment of females typically did not promote male clustering. More generally, our model highlights the conditions that will favor lekking. Lek-like clustering was consistently produced when the benefits in clustering increased in specific nonlinear ways. Our model thus emphasizes clarifying the shapes of relationships between potential selective factors and the size of territory clusters. Key words: dynamic optimization, female preference, lek evolution, predation risk, sexual harassment. [Behav Ecol 14:876–886 (2003)]