Browsing by Author "Spiegel, Orr M."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Data packageData from: Factors influencing foraging search efficiency: Why do scarce lappet-faced vultures outperform ubiquitous white-backed vultures?(2014-09-24) Spiegel, Orr M.; Getz, Wayne M.; Nathan, RanNOTE: A corrected version of this dataset is available. See doi:10.5441/001/1.mf903197 at datarepository.movebank.org/handle/10255/move.401. ABSTRACT: The search phase is a critical component of foraging behavior, affecting interspecific competition and community dynamics. Nevertheless, factors determining interspecific variation in search efficiency are still poorly understood. We studied differences in search efficiency between the lappet-faced vulture (Torgos tracheliotus; LFV) and the white-backed vulture (Gyps africanus; WBV) foraging on spatiotemporally unpredictable carcasses in Etosha National Park, Namibia. We used experimental food supply and high-resolution GPS tracking of free-ranging vultures to quantify search efficiency and elucidate the factors underlying the observed interspecific differences using a biased correlated random walk simulation model bootstrapped with the GPS tracking data. We found that LFV’s search efficiency was higher than WBV’s in both first-to-find, first-to-land, and per-individual-finding rate measures. Modifying species-specific traits in the simulation model allows us to assess the relative role of each factor in LFV’s higher efficiency. Interspecific differences in morphology (through the effect on perceptual range and motion ability) and searchers’ spatial dispersion (due to different roost arrangements) are in correspondence with the empirically observed advantage of LFV over WBV searchers, whereas differences in other aspects of the movement patterns appear to play a minor role. Our results provide mechanistic explanations for interspecific variation in search efficiency for species using similar resources and foraging modes.
- Data packageData from: Factors influencing foraging search efficiency: Why do scarce lappet-faced vultures outperform ubiquitous white-backed vultures? (V2)(2014-11-24) Spiegel, Orr M.; Getz, Wayne M.; Nathan, RanThe search phase is a critical component of foraging behavior, affecting interspecific competition and community dynamics. Nevertheless, factors determining interspecific variation in search efficiency are still poorly understood. We studied differences in search efficiency between the lappet-faced vulture (Torgos tracheliotus; LFV) and the white-backed vulture (Gyps africanus; WBV) foraging on spatiotemporally unpredictable carcasses in Etosha National Park, Namibia. We used experimental food supply and high-resolution GPS tracking of free-ranging vultures to quantify search efficiency and elucidate the factors underlying the observed interspecific differences using a biased correlated random walk simulation model bootstrapped with the GPS tracking data. We found that LFV’s search efficiency was higher than WBV’s in both first-to-find, first-to-land, and per-individual-finding rate measures. Modifying species-specific traits in the simulation model allows us to assess the relative role of each factor in LFV’s higher efficiency. Interspecific differences in morphology (through the effect on perceptual range and motion ability) and searchers’ spatial dispersion (due to different roost arrangements) are in correspondence with the empirically observed advantage of LFV over WBV searchers, whereas differences in other aspects of the movement patterns appear to play a minor role. Our results provide mechanistic explanations for interspecific variation in search efficiency for species using similar resources and foraging modes.
- Data packageData from: Moving beyond curve-fitting: using complementary data to assess alternative explanations for long movements of three vulture species(2015-02-03) Spiegel, Orr M.; Harel, Roi; Centeno-Cuadros, Alejandro; Hatzofe, Ohad; Getz, Wayne M.; Nathan, RanAnimal 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 GPS/accelerometer tags accompanied by behavioral, genetic and morphological data. The Lévy distribution fitted the datasets 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.