Moving beyond curve fitting: Using complementary data to assess alternative explanations for long movements of three vulture species

Orr Spiegel, Roi Harel, Alejandro Centeno-Cuadros, Ohad Hatzofe, Wayne M. Getz, Ran Nathan

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Animal movements exhibit an almost universal pattern of fat-tailed step-size distributions, mixing short and very long steps. The Lévy flight foraging hypothesis (LFFH) suggests a single optimal food search strategy to explain this pattern, yet mixed movement distributions are biologically more plausible and often convincingly fit movement data. To confront alternative explanations for these patterns, we tracked vultures of three species in two very different ecosystems using high-resolution global positioning system/accelerometer tags accompanied by behavioral, genetic, and morphological data. The Lévy distribution fitted the data sets reasonably well, matching expectations based on their sparsely distributed food resources; yet the fit of mixed models was considerably better, suggesting distinct movement modes operating at three different scales. Specifically, long-range forays (LRFs)—rare, short-term, large-scale circular journeys that greatly exceed the typical foraging range and contribute to the tail-fatness of the movement distribution in all three species— do not match an optimal foraging strategy suggested by the LFFH. We also found no support for preferred weather conditions or population genetic structure as alternative explanations, so the hypothesis that LRFs represent failed breeding dispersal attempts to find mates remains our most plausible explanation at this time. We conclude that inference about the mechanisms underlying animal movements should be confronted with complementary data, and suggest that mixed behavioral modes likely explain commonly observed fat-tailed movement distributions.

Original languageEnglish
Pages (from-to)E44-E54
JournalAmerican Naturalist
Volume185
Issue number2
DOIs
StatePublished - 1 Jan 2015
Externally publishedYes

Keywords

  • 3-D accelerometers
  • Fat-tailed step-size distribution
  • Lévy flight foraging hypothesis
  • Movement ecology
  • Sex-biased dispersal
  • Wildlife biotelemetry

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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