A framework for determining the fitness consequences of antipredator behavior

Behavioral ecologists have long been interested in understanding the adaptive value of antipredator behavior (Sih 1987; Lima and Dill 1990; Lima 1998). A recent review by Lind and Cresswell (2005), however, noted some important difficulties with quantifying the fitness consequences of antipredator behaviors. In essence, Lind and Cresswell suggest that most studies do not provide strong evidence on the adaptive value of antipredator behavior because they do not consider 1) trade-offs between antipredator and reproductive performance, 2) the abilities of organisms to avoid fitness losses associated with constraints on focal traits by employing behavioral alternatives (behavioral compensation), and 3) the effects of behavioral defenses at different stages of the predation sequence. The authors rightfully assert that an understanding of these issues can only be accomplished by measuring multiple traits and fitness components (i.e., survival and reproduction). Nevertheless, the question of how to integrate such data into a coherent analysis of adaptive value was left unclear. Our discussion therefore has 2 main goals: 1) to illustrate how the concerns addressed by Lind and Cresswell can be unified and generalized to include a variety of other issues under the conceptual framework of phenotypic integration and 2) to describe 2 quantitative techniques that exist within that framework for addressing the question of adaptive value. We begin by reiterating the main points made by Lind and Cresswell with a hypothetical example (illustrated in Figure 1).