Prey Encounter Rate by Predators: Discussing the Realism of Grid-Based Models and How to Model the Predator's Foraging Mode: A Reply to Avgar et al.

摘要

In an article in this journal (Scharf et al. 2006), we presented an individual-based model (IBM) whose aim was to investigate how gradual changes in the movement directionality and velocity of the predator and prey influence the relative hunting success of an active versus an ambush predator. Our main findings were as follows: (1) As the movements of the predator and prey become more directional, the relative hunting success of the active predator decreases and that of the ambush predator gradually improves. (2) Nondirectionally moving prey is better caught by a directionally than by a nondirectionally moving predator. (3) As expected from analytical models (e.g., Werner and Anholt 1993), an increase in the velocity of the active predator improves its relative hunting success. In their critique of our model, Avgar et al. (2008, in this issue) argued that the way in which we modeled the behavior of the active predator by using sequential actions (i.e., moving first and only then detecting/attacking prey) is problematic. They therefore modified the original code of our model to enable the predator to catch prey items while moving. Whereas in the original model the ambush predator had higher encounter rates than the active predator under some specific conditions, in the modified model this scenario never occurred. Avgar et al. noted that this result better fits the expectations of previous analytical models.