Temporal variation in danger drives antipredator behavior: The predation risk allocation hypothesis

The rapid response of animals to changes in predation risk has allowed beha vioral ecologists to learn much about antipredator decision making. A large ly unappreciated aspect of such decision making, however, is that it may be fundamentally driven by the very thing that allows it to be so readily stu died: temporal variation in risk. We show theoretically that temporal varia bility in risk leaves animals with the problem of allocating feeding and an tipredator efforts across different risk situations. Our analysis suggests that an animal should exhibit its greatest antipredator behavior in high-ri sk situations that are brief and infrequent. An animal should also allocate more antipredator effort to high-risk situations and more feeding to low-r isk situations, with an increase in the relative degree of risk in high-ris k situations. However, the need to feed leaves an animal with little choice but to decrease its allocation of antipredator effort to high-risk situati ons as they become more frequent or lengthy; here, antipredator effort in l ow-risk situations may drop to low levels as an animal allocates as much fe eding as possible to brief periods of low risk. These conclusions hold unde r various scenarios of interrupted feeding, state-dependent behavior, and s tochastic variation in risk situations. Our analysis also suggests that a c ommon experimental protocol, in which prey animals are maintained under low risk and then exposed to a brief "pulse" of high risk, is likely to overes timate the intensity of antipredator behavior expected under field situatio ns or chronic exposure to high risk.