Reciprocal behavioral plasticity and behavioral types during predator-prey interactions

Abstract

How predators and prey interact has important consequences for population dynamics and community stability. Here we explored how predator-prey interactions are simultaneously affected by reciprocal behavioral plasticity (i.e., plasticity in prey defenses countered by plasticity in predator offenses and vice versa) and consistent individual behavioral variation (i.e., behavioral types) within both predator and prey populations. We assessed the behavior of a predator species (northern pike) and a prey species (three-spined stickleback) during one-on-one encounters. We also measured additional behavioral and morphological traits in each species. Using structural equation modeling, we found that reciprocal behavioral plasticity as well as predator and prey behavioral types influenced how individuals behaved during an interaction. Thus, the progression and ultimate outcome of predator-prey interactions depend on both the dynamic behavioral feedback occurring during the encounter and the underlying behavioral type of each participant. We also examined whether predator behavioral type is underlain by differences in metabolism and organ size. We provide some of the first evidence that behavioral type is related to resting metabolic rate and size of a sensory organ (the eyes). Understanding the extent to which reciprocal behavioral plasticity and intraspecific behavioral variation influence the outcome of species interactions could provide insight into the maintenance of behavioral variation as well as community dynamics.

Figure 1

The general hypotheses underlying the a priori structural equation model. Solid arrows indicate direct effects, and the dashed double-headed arrow indicates where reciprocal behavioral plasticity might occur. The white box indicates prey traits, and the gray box indicates predator traits. Line drawings by K. E. McGhee.

Figure 2

Path diagram for the structural equation model with standardized regression weights for stickleback (ST) behavior (white boxes) and pike behavior (gray boxes). Statistically significant paths are indicated by solid arrows, and the strength of these relationships is indicated by the width of the arrows. Nonsignificant paths are indicated by gray dashed arrows. Straight arrows reflect causal paths; curved arrows designate correlations. The R² values in each box indicate the amount of variation in that variable that is explained by the input arrows. Stars indicate the paths allowing behavioral feedback between predator and prey; N = 77 interactions. The standardized coefficients in these path diagrams are measured in standard deviation units.

Figure 3

Proportion of time stickleback spent frozen with pike relative to time to capture. The greater the proportion of time prey spent frozen during an encounter with a live predator, the longer they survived.

Figure 4

Average predatory behavior during the predation assay was negatively correlated with resting metabolic rate (A) and eye mass (B), after accounting for body mass.