在一个食物来源不集中、不可预测的生境中找到食物的最好方式是什么？理论表明，觅食的生物应采取一种“Lévy-flight”搜索策略，它是“随机行走”的一个变异形式，在这种形式的行走中，短距离的探索性蹦蹦跳跳与偶尔较长距离的行走相间。但当捕食者发现它们自己周围有丰足的食物时，简单的不规则运动或“布朗”运动就应当足够了。
事实证明，野生动物中有关真正的“Lévy-flight”式觅食的明显证据难以获得，但是现在，对包括鲨鱼、大马林鱼（枪鱼）和金枪鱼在内的14个海洋捕食者物种构成的一个大型数据集所做的一项分析证明了这一点。电子标记显示，当在生产力较低、猎物稀少的水域游动时，鱼类采取Lévy行为；而在生产力较高的生活环境中时，它们则采用“布朗”运动方式。（生物谷Bioon.net）
生物谷推荐原文出处：
Nature doi:10.1038/nature09116
Environmental context explains Lévy and Brownian movement patterns of marine predators
Nicolas E. Humphries,Nuno Queiroz,Jennifer R. M. Dyer,Nicolas G. Pade,Michael K. Musyl,Kurt M. Schaefer,Daniel W. Fuller,Juerg M. Brunnschweiler,Thomas K. Doyle,Jonathan D. R. Houghton,Graeme C. Hays,Catherine S. Jones,Leslie R. Noble,Victoria J. Wearmouth,Emily J. Southall& David W. Sims
An optimal search theory, the so-called Lévy-flight foraging hypothesis1, predicts that predators should adopt search strategies known as Lévy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey2, 3, 4. Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Lévy behaviour has recently been questioned5, 6. Consequently, whether foragers exhibit Lévy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory’s central predictions. Here we use maximum-likelihood methods to test for Lévy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Lévy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Lévy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Lévy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Lévy-flight foraging hypothesis1, 7, supporting the contention8, 9 that organism search strategies naturally evolved in such a way that they exploit optimal Lévy patterns.
