The allometrics of fear: Interspecific relationships between body size and response to predation risk

Background/Question/Methods: Body size is associated with fundamental biological processes such as metabolism, movement, and the rate of reproduction and evolution. Although allometric principles should also influence the range of potential behavioral responses for a given organism, evidence for such large-scale and cross-taxon relationships is lacking. If they exist, scaling-related changes in behavior should be particularly prominent in predator-prey interactions: body size affects the likelihood of attack and the costs of predator avoidance. We take a interspecific perspective on a traditionally intraspecific topic by using a 142-species data set containing organisms ranging over seven degrees of magnitude in body size to analyze the relationship between mean response to predation risk and both prey size and the predator:prey size ratio.

Results/Conclusions: We found a weak but consistently negative relationship between mean species-level prey mass and four of the five response variables; in contrast, only two of five response variables were correlated with predator:prey size ratios. While the weakness of the relationship highlights the fact that behavior is primarily influenced by intraspecific factors, the consistently negative correlation with prey mass suggests that underlying allometric relationships may play a subtle underlying role in structuring large-scale patterns of behavior.