Predator-Prey Interactions

Abstract

Predator-prey interactions have been among the most intensively studied areas of aquatic biology during the past several decades. Investigations have focused particularly on theories of “optimal foraging,” which seeks to describe predator behavior [e.g., Charnov (1976), Werner and Hall (1974), and Pyke (1984)], and “predator mediated community structure” (Hrbacek, 1962; Brooks and Dodson, 1965; Hall et al., 1976; Zaret, 1980; Werner and Gilliam, 1984; Sih et al., 1985; Kerfoot and Sih, 1987; Lampert and Sommer, 1997), which interprets community structure in relation to predatory activities. Many of these hypotheses still are speculative, although supporting evidence for some is growing. These concepts form a useful basis for the study of predator-prey relationships. The literature on this subject is extremely large; a few summary articles relative to limnology are cited in this exercise.

In evaluating predator-prey interactions, both the predators and prey have physiological and behavioral characteristics that must be considered. Major predator characteristics that can be evaluated include: (1) visual, mechanical, or chemical detection of prey; (2) how much energy is required during searching for and attacking prey; and (3) energy and time expended in handling, and total or partial consumption of prey. Evaluation of the ways in which prey respond to predation requires considerations of: (1) behavior and energy expended in escape responses, often by refuge in space and/or time; and (2) means by which prey adapt and coexist with predators. The latter coexistence can be accomplished by camouflage, differences in size, release of repulsive chemical compounds, frightening displays, evasive movements, morphological structures that impede or prevent consumption, and aggregation in large groups.

Predators and prey respond continuously to each other’s adaptations, which results in constant, although slow, coevolution and changing interactions. The extent of interactive couplings can be evaluated by exposing prey to predators under controlled experimental conditions [e.g., Thompson (1978) and Werner (1974)] or by the introduction of new predators or prey into established ecosystems [e.g., Langeland (1981) and Morgan et al. (1978)]. The latter approach should not be done without considerable forethought and understanding of ecosystem properties. The former experimental approach will be used in this exercise to gain insight into some basic predator-prey interactions.