Effects of temporal variation in predation risk on predator-prey interactions

Studies of predator-prey interactions and trophic dynamics have primarily focused on the effects of chronic presence or absence of predators on the behavior of intermediate prey. Lacking in these experiments is the understanding of how prey respond to more natural conditions of temporal variations of predation risk. The Risk Allocation Hypothesis (RAH) suggests that optimal prey behavior is dependent on the overall pattern of predation risk experienced by that animal over time. To test this hypothesis we manipulated the presence and absence of a top predator in two common subsets of an estuarine food web while monitoring the behavior and foraging efforts of intermediate predators. The intermediate predators from the two different subsets showed different behavioral responses to variations in predation risk over time. Support of the risk allocation hypothesis was evident in one of the systems but not in the other suggesting that overall impacts through out the food web are dependent on the species involved. More specifically, based on the results from this study, the cascading effect of the top predator is suggested to be dependent on how the intermediate predators assess the magnitude and pattern of risk that it is exposed to.