Conditions favoring anticipatory and reactive displays deflecting predatory attack

Abstract

Deflective displays direct predatory attacks to body parts that are relatively invulnerable or can be lost without disastrous consequences. Usually, these behaviors are directed to predators poised to attack at very close quarters. In contrast to such reactive deflection is anticipatory deflection in situations that entail a high risk of being ambushed. Because a predator can draw nearer during display, reactive deflection is feasible only when the predator is already close. A graphical model shows lines relating probability of death to distance from the predator when the prey displays and when it flees without display. Reactive deflection decreases the probability of death when the predator is closer than the intersection of these lines, but increases the probability of death beyond the intersection. If the predator is detected when far enough away, the best option is to flee without displaying. Anticipatory deflection may increase the probability of surviving ambush immediately after arriving at a new location but increase the risk of attracting the attention of other predators. This risk increases with time since stopping as more predators arrive that did not detect the prey moving to its new location. Anticipatory deflection can be selectively favored only during a brief interval immediately after the prey arrives. The interval increases with benefit of display to survival if ambushed. It decreases with increases in probabilities of being detected and killed due to display. Examples of these displays and other taxa in which they may be sought are discussed.