Alternative forms of competition and predation dramatically affect habitat selection under foraging-predation-risk trade-offs

Abstract

Habitat selection under foraging-predation-risk trade-offs has been a frequent topic of interest to theoretical behavioral and evolutionary ecologists. However, most habitat selection models assume that individuals compete exploitatively for resources and that predation is either density independent or diluted completely by competitor number, despite empirical evidence that other forms of competition and predation also occur in nature. I developed an individual-based model for studying the effects of alternative forms of competition and predation on the process of habitat selection under foraging-predation-risk trade-offs. To make the model more relevant to natural populations, I assumed that individuals vary continuously in traits related to competitive ability and vulnerability to predation and allowed resources and predators to be distributed across more than two habitats. The results of my investigation demonstrate that the predicted pattern of habitat selection can be affected dramatically by the form predation is assumed to take. When predation is density dependent or frequency dependent, individuals will tend to be distributed across habitats according to their absolute vulnerability to predation. In contrast, when predation is density dependent or vulnerability dependent, individuals will tend to segregate by competitive ability. Whether one assumes that individuals compete for resources via exploitation or interference also influences the predicted pattern of habitat selection. In general, interference competition results in a more even distribution of competitors across habitats.