title: Generalized Pareto for Pattern-Oriented Random Walk Modelling of Organisms' Movements.
abstract: How organisms move and disperse is crucial to understand how population dynamics relates to the spatial heterogeneity of the environment. Random walk (RW) models are typical tools to describe movement patterns. Whether Lévy or alternative RW better describes forager movements is keenly debated. We get around this issue using the Generalized Pareto Distribution (GPD). GPD includes as specific cases Normal, exponential and power law distributions, which underlie Brownian, Poisson-like and Lévy walks respectively. Whereas previous studies typically confronted a limited set of candidate models, GPD lets the most likely RW model emerge from the data. We illustrate the wide applicability of the method using GPS-tracked seabird foraging movements and fishing vessel movements tracked by Vessel Monitoring System (VMS), both collected in the Peruvian pelagic ecosystem. The two parameters from the fitted GPD, a scale and a shape parameter, provide a synoptic characterization of the observed movement in terms of characteristic scale and diffusive property. They reveal and quantify the variability, among species and individuals, of the spatial strategies selected by predators foraging on a common prey field. The GPD parameters constitute relevant metrics for (1) providing a synthetic and pattern-oriented description of movement, (2) using top predators as ecosystem indicators and (3) studying the variability of spatial behaviour among species or among individuals with different personalities.
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR212 EME, Centre de Recherche Halieutique Méditerranéenne et Tropicale, Avenue Jean Monnet, BP 171, 34203 Sète Cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Bertrand
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR212 EME, Centre de Recherche Halieutique Méditerranéenne et Tropicale, Avenue Jean Monnet, BP 171, 34203 Sète Cedex, France; IMARPE, Esquina Gamarra y General Valle S/N Chucuito, Callao, Lima, Peru.
authors.forename: Rocío
authors.initials: R
authors.lastname: Joo
authors.affiliation: Institut TELECOM; TELECOM Bretagne; UMR CNRS 3192 Lab-STICC, Technopôle Brest Iroise CS 83818, 29238 Brest cedex, France.
authors.forename: Ronan
authors.initials: R
authors.lastname: Fablet
mesh_terms: D063147:Animal Distribution; D000818:Animals; D004058:Diffusion; D017753:Ecosystem; D006801:Humans; D015233:Models, Statistical; D009038:Motion; D009068:Movement; D010363:Pattern Recognition, Automated; D012767:Ships; D013269:Stochastic Processes