Multiscale Habitat Selection and Road Avoidance of Elk on their Winter Range

Abstract

Roads are a prevalent, ever-increasing form of human disturbance on the landscape. In many places in western North America, energy development has brought human and road disturbance into seasonal winter range areas for migratory elk. In this population, I studied individual habitat selection relative to road proximity at two scales to quantify factors influencing among- and within-home-range selection of winter range. Further, I sough to evaluate predictions from the risk-disturbance hypothesis when studying fine-scale movement and selection response to roads during winter. I outlined availability extents for 107 individual elk-years based on observed fall migration distance, and with a minimum convex polygon around winter telemetry relocations. To model the response by elk to road disturbance, I fit a resource selection model to each elk-year, and examined population-level and individual variation in the movement response. In addition, I evaluated the relationship between inferred selection at the two scales and the functional response in selection. In addition, I used integrated Step Selection Analysis (iSSA) to evaluate four alternative hypotheses regarding the influence of roads on space-use behaviour across 175 elk-years of elk telemetry data, and I quantify both population and individual variation in responses. Road proximity and crossing were used to evaluate these behaviours, which offered a rare comparison between two common measures of roads. Roads had a ubiquitous influence on elk across scales. Elk, individually and as a population, avoided roads when migrating to their winter range and within this home range. Individual elk that avoided roads more strongly relative to the population did so at both scales of analysis. Our results thus support bottom-up habitat-selection patterns, where the underlying behaviours are not scale-dependent. Further, I demonstrated, for the first time, how iSSA can be used to marry movement analysis in a refined approach to habitat selection. Elk responded to roads as they would natural predation risk. Elk selected areas farther from roads at all times of day with avoidance being greatest during twilight. In addition, elk sought cover and moved more when in the vicinity of roads. Road crossings were generally avoided, but this avoidance was weakest during daytime when elk were both moving and closer to roads. Energy development is transforming landscapes in western North America with the proliferation of roads, which I show is having substantial and multifaceted negative effects on elk behaviour across multiple scales. Consequently, any new road construction or increases in existing road-use intensity would have detrimental effects on migratory elk populations by restricting space-use.