title: Density-dependent prey mortality is determined by the spatial scale of predator foraging.
abstract: Foraging theory predicts which prey patches predators should target. However, in most habitats, what constitutes a 'patch' and how prey density is calculated are subjective concepts and depend on the spatial scale at which the predator (or scientist) is observing. Moreover, the predator's 'foraging scale' affects prey population dynamics: predators should produce directly density-dependent (DDD) prey mortality at the foraging scale, but inversely density-dependent (IDD) mortality (safety-in-numbers) at smaller scales. We performed the first experimental test of these predictions using behavioral assays with guppies (Poecilia reticulata) feeding on bloodworm 'prey' patches. The guppy's foraging scale had already been estimated in a prior study. Our experimental results confirmed theoretical predictions: predation was IDD when prey were aggregated at a scale smaller than the foraging scale, but not when prey were aggregated at larger scales. These results could be used to predict outcomes of predator-prey interactions in continuous, non-discrete habitats in the field.
authors.affiliation: Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC, 28403, USA.|Department of Geography and Geology, University of North Carolina Wilmington, Wilmington, NC, 28403, USA.
authors.forename: Erin K
authors.initials: EK
authors.lastname: McCarthy
authors.affiliation: Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC, 28403, USA. whitejw@uncw.edu.
authors.forename: J Wilson
authors.initials: JW
authors.lastname: White
mesh_terms: D000818:Animals; D017753:Ecosystem; D020387:Food Chain; D009026:Mortality; D011036:Poecilia / Q000502:physiology*; D011156:Population Density; D011157:Population Dynamics; D011235:Predatory Behavior
keywords: Foraging scale; Foraging theory; Patch selection; Predator–prey interactions; Scale-dependent interactions