Breed Greg A, Severns Paul M, Edwards Andrew M
Department of Biological Sciences, University of Alberta, Edmonton, Canada AB T6G 2E9
Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis, OR, USA.
J R Soc Interface. 2015 Feb 6;12(103). doi: 10.1098/rsif.2014.0927.
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight.
Lévy飞行在动物运动分析中备受关注。在Lévy飞行中，步长取自重尾分布，如幂律（PL），并且已经发表了大量的实证证明。然而，其他人认为动物运动并不适合PL分布，或者认为状态转换过程能更好地解释明显的Lévy飞行运动模式。我们结合直接行为观察和GPS跟踪来了解两种相关蝴蝶雌性的步长模式。我们最初发现，一种蝴蝶（泰勒银斑弄蝶Euphydryas editha taylori）的运动最适合有界PL，这是Lévy飞行的证据，而另一种（辉银斑弄蝶Euphydryas phaeton）则最适合指数分布。后续分析引入了更多候选模型，并利用行为观察根据种内相互作用对步长进行分类（种内相互作用在辉银斑弄蝶中很少见，但在泰勒银斑弄蝶中很常见）。这些分析表明，混合指数分布比泰勒银斑弄蝶的有界PL更受青睐，并且当根据骚扰同种雄性的影响将步长分类为不同状态时，两种状态都最适合简单指数分布。直接行为观察使我们能够推断出潜在的行为机制是由种内相互作用驱动的状态转换过程，而不是Lévy飞行。
