Patterns of Prey Selection: Implications of Predator Foraging Tactics

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Abstract
In this paper, I explore the consequences of different predator foraging tactics on patterns of prey selection. Foraging tactics are categorized on the basis of two dichotomies, the first concerning predator encounter tactics and the second concerning the handling tactics employed by predators to subdue prey. The former dichotomy distinguishes between ambush and cruishing encounter tactics, the latter bewtween entangling and raptorial handling tactics. Two consistent trends in prey selection are revealed by examining the patterns of prey selection exhibited by a variety of zooplanktivorous, invertebrate predators. The first trend concerns the tendency of ambush predators to take larger and older prey, relative to those taken by cruising predators. This trend was predicted and is presumed to be a general feature of predator-prey interactions. The second trend concerns the tendency of ambush predators feeding on Calanus to exhibit bimodal prey-selection patterns, in contrast to the unimodal patterns exhibited by cruisers. This trend was not predicted and is certainly not a general feature of predator-prey interactions, but it does serve to illustrate the heuristic value of the ambush-cruising dichotomy. At present, too few studies are available to compare trends associated with the entangling-raptorial dichotomy. However, a brief discussion of the potential interaction effects between predator foraging tactics and prey defensive tactics points out that both dichotomies merit closer examination.