Fractal analysis can explain individual variation in dispersal search paths

Veronica A.J. Doerr, Erik D. Doerr

    Research output: Contribution to journalReview articlepeer-review

    48 Citations (Scopus)

    Abstract

    The use of fractal analysis to study animal movement paths has been criticized because the inherent assumptions of the technique are rarely discussed, and most movement paths violate the assumption of scale invariance. While this violation may prohibit the use of the technique for population-level prediction, it need not restrict the analysis of individual variation in movement patterns, an application of fractal theory that has received relatively little research attention. Therefore, we review fractal analysis and its assumptions, highlighting three ways in which it can yield useful information about individual movement paths regardless of whether or not the assumption of scale invariance has been met. We used these techniques to analyze patterns of individual variation and potential causes of variation in the dispersal searching paths of two species of Australian treecreeper (Passeriformes: Climacteridae). By comparing relative fractal D, or the relative tortuosity and thus thoroughness of search paths, we found that individuals faced a trade-off between thoroughness and the extent of searching. Thoroughness also differed between the sexes and the species, possibly as a direct consequence of mating and social systems. For almost all individuals, thoroughness varied depending on the spatial scale at which it was examined, revealing three distinct domains of scale in which movement tactics vary because movement is used for very different purposes. Variability in movement tactics was greatest in the largest spatial-scale domain, the one used exclusively for dispersal movements, suggesting that dispersal tactics show more intraspecific variation than other types of movement because dispersal, decisions are influenced by a greater variety of factors. Our results reveal that fractal analysis can provide useful information on the causes of and constraints on individual movement strategies, creating empirically based models of animal movement and thus a firm foundation for modeling movement processes from individual to landscape scales.

    Original languageEnglish
    Pages (from-to)1428-1438
    Number of pages11
    JournalEcology
    Volume85
    Issue number5
    DOIs
    Publication statusPublished - May 2004

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