Habitat selection differs across hierarchical behaviors: Selection of patches and intensity of patch use: Selection

Abstract

When animals select habitats, they integrate a suite of behaviors that are influenced by multiple competing resource requirements. Resources that influence decisions about habitat use are likely to differ across spatial scales and hierarchical behaviors. At coarser scales, animals are expected to select resources that are critical to fitness, and at finer scales, to intensively use resources that enhance fitness. Our goal was to contrast habitat selection at two hierarchical behavioral levels (patch selection and intensity of patch use) to test hypotheses about how resources shape habitat use. We applied a two-stage hurdle model to quantify both initial selection and intensity of use of resource patches by a burrowing herbivore, the pygmy rabbit (Brachylagus idahoensis). We expected security from predation to influence initial selection of patches, and forage availability to influence intensity of use of selected patches. We monitored locations of adults fitted with radio-collars during winter and summer. We measured vegetation, burrow characteristics, and concealment cover within patches that were used and unused by rabbits, and we quantified burrow densities surrounding patches in a GIS. Selection of used patches from available patches was largely influenced by security resources (presence and proximity of burrows, shrub height, and woody ground cover) during both seasons. Intensity of patch use was also influenced by forage availability and, consequently, differed between seasons. During winter, sagebrush is the primary forage, and greater sagebrush canopy within a patch was associated with increased intensity of use. During summer, rabbits more intensively used patches with greater availability of herbaceous forage. Elucidating how animals make choices about habitats across a diversity of spatial and temporal scales will continue to increase our understanding of the factors that govern distribution of populations and movements of individuals. By extending these concepts to hierarchical behaviors, we can enhance insights into the processes that shape the patterns of habitat use we observe.