Linking habitat heterogeneity to space use by large herbivores at multiple scales: From habitat mosaics to forest canopy openings

Although habitat selection and home range size of herbivores in forested landscapes are generally related to the composition and spatial arrangement of open and forested habitat categories, it is unclear how herbivores respond to finer habitat mosaics such as more productive canopy openings within forest stands. We aimed to determine the relationships between habitat selection and home range size of 32 white-tailed deer (Odocoileus virginianus) females and spatial heterogeneity in forage and cover at multiple scales. We used GPS telemetry to delineate summer and winter home ranges and to evaluate habitat selection. We used landscape metrics to measure spatial heterogeneity of open and closed habitat categories within each home range and in three circles of radii of 1000, 2000 and 3000 m centered on each home range, and field surveys to quantify spatial patterns in canopy openings within forest stands. Deer responded to forage abundance at multiple scales during summer, as they selected peatlands within the landscape, canopy openings within forest stands, and reduced the size of their home range with increasing forbs and deciduous shrubs cover. Deer also responded to forage abundance during winter as they selected areas with high proportions of food-rich balsam fir stands to establish their home range and had a smaller home range size when the density of food sources increased. However, in areas where the proportion of food-rich balsam fir stands was less available, deer selected heterogeneous habitat mosaics to settle their winter home range. Moreover, deer responded positively to edge density of cutblocks only during winter and they did not select canopy openings during that season. Winter forage such as windblown fir trees were highly associated to edges between clear-cuts and balsam fir stands making these large openings an important element of deer winter habitat in ecosystem modified by long-term browsing. Our results emphasize the significance of considering multiple and nested mosaics of openings and continuous cover when assessing habitat selection patterns and home range size of herbivores living in forested landscapes, as the influence of spatial heterogeneity in resources varied with the constraints of seasonal environments.

► We used GPS telemetry to monitor deer habitat selection during summers and winters.
► We quantified spatial heterogeneity in forested landscapes at multiple spatial scales.
► Multiple and nested mosaics of openings and continuous cover influenced habitat selection.
► Deer responses to spatial heterogeneity varied with seasonal constraints.
► We report a mechanism that contributes to the maintenance of long-term high deer densities.