Abstract
BackgroundThe Lévy flight foraging hypothesis predicts a transition from scale-free Lévy walk (LW) to scale-specific Brownian motion (BM) as an animal moves from resource-poor towards resource-rich environment. However, the LW-BM continuum implies a premise of memory-less search, which contradicts the cognitive capacity of vertebrates.ResultsWe describe methods to test if apparent support for LW-BM transitions may rather be a statistical artifact from movement under varying intensity of site fidelity. A higher frequency of returns to previously visited patches (stronger site fidelity) may erroneously be interpreted as a switch from LW towards BM. Simulations of scale-free, memory-enhanced space use illustrate how the ratio between return events and scale-free exploratory movement translates to varying strength of site fidelity. An expanded analysis of GPS data of 18 female red deer, Cervus elaphus, strengthens previous empirical support of memory-enhanced and scale-free space use in a northern forest ecosystem.ConclusionA statistical mechanical model architecture that describes foraging under environment-dependent variation of site fidelity may allow for higher realism of optimal search models and movement ecology in general, in particular for vertebrates with high cognitive capacity.Electronic supplementary materialThe online version of this article (doi:10.1186/2051-3933-1-9) contains supplementary material, which is available to authorized users.
Highlights
The Lévy flight foraging hypothesis predicts a transition from scale-free Lévy walk (LW) to scalespecific Brownian motion (BM) as an animal moves from resource-poor towards resource-rich environment
LW contrasts with a more scale-specific and “finegrained” kind of movement, Brownian motion (BM), which may be expected to arise in environments with more frequent responses to events and conditions within the perceptual range resulting in low degree of directional persistence of the path
By aid of simulations of this alternative model we demonstrate an apparently similar shift in LW towards BM as under the LFF hypothesis’ modal shift, but where the transition appear from scale-free movement spanning low towards high ratio of return steps relative to ordinary search steps; i.e., increased strength of site fidelity
Summary
The Lévy flight foraging hypothesis predicts a transition from scale-free Lévy walk (LW) to scalespecific Brownian motion (BM) as an animal moves from resource-poor towards resource-rich environment. The Lévy flight foraging (LFF) hypothesis extends the theory of optimal foraging by bringing a closer attention to the distinction between scale-free and scale-specific movement [2,3,4] It has arisen as a result of a constructive interplay between simulation models identifying optimal space use tactics under given environmental conditions [3,5] and empirical testing of these predictions on animal movement data [6,7,8,9]. LW contrasts with a more scale-specific and “finegrained” kind of movement, Brownian motion (BM), which may be expected to arise in environments with more frequent responses to events and conditions within the perceptual range resulting in low degree of directional persistence of the path One such event could for example be detection and handling of a food item, followed by a new displacement that is independent on the foregoing ones. The medium range steps are in this case rarer than for LW and the longest ones are completely absent
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