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

Abstract

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.

Habitat specialists as conservation umbrellas: Do areas managed for greater sage‐grouse also protect pygmy rabbits?

“…The most important variables included distribution of big sagebrush (Table 3). Sagebrush vegetation is central to pygmy rabbit survival as a food source and the primary structural component of their habitat, and both density and height of sagebrush have been consistently associated with habitat use by pygmy rabbits (Green and Flinders 1980, Weiss and Verts 1984, Katzner and Parker 1997, Heady and Laundr e 2005, McMahon et al 2017. Sagebrush height was not a strong predictor in our SDM, which is likely a function of variation in shrub height across the pygmy rabbit range.…”

“…comprised up to 99% of pygmy rabbit winter diets and about 50% of summer diets (Shipley et al 2006), and pygmy rabbits occurred at sites with relatively dense and tall sagebrush vegetation (Katzner and Parker 1997, Lee et al 2010, McMahon et al 2017. For example, big sagebrush (Artemisia tridentata spp.)…”

“…For example, big sagebrush (Artemisia tridentata spp.) comprised up to 99% of pygmy rabbit winter diets and about 50% of summer diets (Shipley et al 2006), and pygmy rabbits occurred at sites with relatively dense and tall sagebrush vegetation (Katzner and Parker 1997, Lee et al 2010, McMahon et al 2017. To that end, we selected variables that measured the extent of big sagebrush communities, the majority shrub canopy cover, majority percent herbaceous cover, and the maximum and majority shrub height within a 90 m neighborhood (3 9 3 cell).…”

“…Two general habitat features are associated with the year-round presence of pygmy rabbits: (1) relatively dense and tall sagebrush vegetation and (2) soil characteristics that are conducive to burrowing, such as the presence of deep, loamy soils, and features such as alluvial fans and Mima mounds (Borell and Ellis 1934, Weiss and Verts 1984, McMahon et al 2017. Two general habitat features are associated with the year-round presence of pygmy rabbits: (1) relatively dense and tall sagebrush vegetation and (2) soil characteristics that are conducive to burrowing, such as the presence of deep, loamy soils, and features such as alluvial fans and Mima mounds (Borell and Ellis 1934, Weiss and Verts 1984, McMahon et al 2017.…”

“…Although sage-grouse and pygmy rabbits are both sagebrush obligates, their resource needs likely differ at least during some periods of the annual cycle. Two general habitat features are associated with the year-round presence of pygmy rabbits: (1) relatively dense and tall sagebrush vegetation and (2) soil characteristics that are conducive to burrowing, such as the presence of deep, loamy soils, and features such as alluvial fans and Mima mounds (Borell and Ellis 1934, Weiss and Verts 1984, McMahon et al 2017. Unlike pygmy rabbits, sage-grouse shift habitat use across the year, and biologists often consider spring breeding, summer brood rearing, and winter habitats as distinct (Fedy et al 2014, Rice et al 2016.…”