Predator–prey population dynamics may induce the evolutionary dynamics of behavioral unpredictability

Behavioral unpredictability (within-individual behavioral variability that cannot be explained by extrinsic and intrinsic factors) has been observed in a wide variety of species, but its adaptive significance is not well understood. This study examines the possibility that behavioral unpredictability is maintained through predator–prey population dynamics. An individual-based model was constructed to track the status of individual predators. The handling time of a predator is characterized by its expected value and unpredictability, which are heritable, and each predator features a unique combination of these characteristics. A discrete generation model in which one prey species and one predator species interact was constructed. The model showed that the evolutionarily stable strategy (ESS) of handling time is associated with no behavioral unpredictability and that the ESS handling time depends on the densities of the prey and predators. When populations exhibit cyclic dynamics, the ESS also changes along with the population dynamics, thereby creating mismatches between the traits of predators and the ESS because the dynamics of the ESS and population are faster than the evolution of the handling time traits. This mismatch can generate conditions in which individuals with behavioral unpredictability are at least transiently selected because of the topology of the fitness landscape. However, the model also showed that the selection strength of behavioral unpredictability is weak and can be overruled by inherent stochastic processes.