REEXAMINING SAFETY IN NUMBERS - INTERACTIONS BETWEEN RISK DILUTION AND COLLECTIVE DETECTION DEPEND UPON PREDATOR TARGETING BEHAVIOR

Many studies document that individuals visually scan for predators les s frequently when in the safety of larger groups. This widely replicat ed effect has generally been explained in terms of distinct predator d etection and risk-dilution effects. We show that a strict distinction between detection and dilution disappears when information about attac ks is imperfectly shared (as it is in reality). Furthermore, dilution and detection effects change depending on when during an attack the pr edator targets a particular prey individual for pursuit. Realistic det ection and dilution effects probably interact with each other and also with the targeting behaviour of predators. Instead of considering det ection and dilution effects on vigilance, it may be more profitable to consider each prey's probability of being targeted during an attack a nd its probability of escaping if attacked. This perspective emphasize s that a full understanding of safety in numbers requires an understan ding of predator targeting strategies.