Description
Disease plays a major role in shaping wildlife populations worldwide and changes in landscape conditions can significantly influence risk of pathogen exposure which can pose a threat to vulnerable wild species. Three viruses that cause hemorrhagic disease affect cervid populations in the U.S. (adenovirus hemorrhagic disease, bluetongue disease, and epizootic hemorrhagic disease) but little is known of their distribution and prevalence in wild populations. We explored the distribution and co-occurrence of seroprevalence of these three pathogens in southern mule deer (Odocoileus hemionus fuliginatus), a subspecies of conservation concern and a harvested species native to southern California, to evaluate the distribution of exposure to these pathogens relative to landscape attributes. We found that habitat type, level of development, and proximity to livestock may affect hemorrhagic disease seroprevalence in southern mule deer. Then using movement data from 64 GPS-collared deer monitored over two years, we assessed patterns and drivers of southern mule deer home range selection and size following a two-step approach. First, we implemented home range selection functions for the wet and dry seasons to examine variation in selection and avoidance of environmental factors. We then used home range selection results to evaluate the relative impact of extrinsic environmental factors in combination with intrinsic demographic factors on southern mule deer home range size. We found that deer were present in areas with lower elevations and steeper slopes and avoided areas in close proximity to roads. We also found that deer use of high-quality forage, measured as satellite-derived normalized difference vegetation index (NDVI), and water sources varied between the wet and dry seasons. These variations in resource use, along with the intrinsic variables of sex and age, played a role in determining home range size of the southern mule deer. These results indicate that the most limited resources in the environment, water and forage, affect southern mule deer populations and highlight the importance of evaluating the combined intrinsic and extrinsic factors of home range size and composition to inform management practices.
