Energetic dynamics and anuran breeding phenology : insights from a dynamic game

Abstract

We designed a dynamic optimization model to examine anuran-breeding phenologies. We evaluated the fitness consequences for males adopting one of four alternative strategies: calling, satelliting, foraging, or hiding. Various factors potentially influence male behavior, including energy reserves, predation risk, cost of calling, probability of finding food, distribution of male energy states in the population, and probability of surviving to another breeding season. We manipulated these parameters to determine how strongly each affects breeding phenology and chorus structure. Manipulating parameters related to the energetic costs and benefits of individual decisions, we generated the three basic patterns of anuran breeding phenology: explosive, continuous, and prolonged breeding with episodic chorusing. Increasing the probability of successful foraging caused a shift from an explosive pattern to a prolonged, episodic chorusing pattern. Decreasing the calling cost resulted in continuous chorusing. Our model predicted that satelliting will be a rare strategy adopted by individuals with relatively low energy reserves. Additionally, individuals adopting the satellite strategy should alternate among satelliting, foraging, and calling as their energy reserves fluctuate. Our results suggest that energetic costs of reproduction and resource limitation may be crucial factors influencing the phenology of anuran chorusing. We propose that under varying conditions of resource availability, male decisions are the consequence of two strategies: a starvation minimization strategy and an energy-state maximization strategy.