Chapter 4 - Antipredator Vigilance: Theory and Testing the Assumptions

Abstract

Vigilance allows individuals to detect predators before they come fatally close. Vigilance is considered costly in the sense that it reduces the time available to perform other fitness-enhancing activities, such as sleeping or foraging. This chapter reviews influential models of antipredator vigilance and examines the evidence to support key assumptions. Recent models of vigilance consider the possibility that groups may include cheaters who invest little in vigilance and the notion that detectors of predation threats can have an advantage in escaping over indirect detectors. Many empirical studies have questioned the validity of several assumptions of vigilance models, including instantaneous and sequential randomness in the initiation of vigilance scans and independence of vigilance among group members. Departures from randomness create sequences of vigilance acts that are more predictable through time. There is also some evidence that instead of acting independently, individuals may synchronize or even coordinate their vigilance.