Scannell J, Roberts G, Lazarus J
Department of Psychology, University of Newcastle upon Tyne, UK.
Proc Biol Sci. 2001 Mar 7;268(1466):541-7. doi: 10.1098/rspb.2000.1388.
Anti-predator scans by animals occur with very irregular timing, so that the initiation of scans resembles a random, Poisson-like, process. At first sight, this seems both dangerous (predators could exploit the long intervals) and wastefull (scans after very short intervals are relatively uninformative). We explored vigilance timing using a new model that allows both predators and prey to vary their behaviour. Given predators that attack at random with respect to prey behaviour, constant inter-scan intervals minimize predation risk. However, if prey scan regularly to minimize their risk from randomly attacking predators, they become more vulnerable to predators that initiate attacks when the inter-scan intervals begin. If, in order to defeat this tactic, prey choose extremely variable inter-scan intervals, they become more vulnerable to predators who wait for long intervals before launching attacks. Only if predators can monitor the variability of inter-scan intervals and either attack immediately (if variability is too low) or wait for long intervals to attack (if variability is too high) does the empirically observed pattern of Poisson-like scanning become the optimal prey strategy.
动物的反捕食扫描时机极不规律，因此扫描的开始类似于一个随机的、泊松分布般的过程。乍一看，这似乎既危险（捕食者可能利用长时间间隔）又浪费（间隔很短后进行的扫描相对没有什么信息价值）。我们使用一种新模型来探究警戒时机，该模型允许捕食者和猎物都改变其行为。对于随机根据猎物行为发起攻击的捕食者而言，恒定的扫描间隔能将捕食风险降至最低。然而，如果猎物定期进行扫描以将来自随机攻击的捕食者的风险降至最低，那么它们就更容易受到在扫描间隔开始时发起攻击的捕食者的攻击。如果为了应对这种策略，猎物选择极其多变的扫描间隔，那么它们就更容易受到等待很长时间才发动攻击的捕食者的攻击。只有当捕食者能够监测扫描间隔的变化性，并要么立即发动攻击（如果变化性过低），要么等待很长时间才发动攻击（如果变化性过高）时，经验观察到的类似泊松分布的扫描模式才会成为最优的猎物策略。
