Synergistic Effects of Road Closure, Climate and Vegetation Change on Elk Counts: Implications for Management

Abstract

Increasing our understanding of the effects motor vehicles have on elk populations is vital to their management and past research has consistently shown that elk avoid roads and traffic. However, the fine-scale impact of traffic volume is rarely quantified and the environmental context experienced by elk at the time of disturbance is systematically ignored in these studies. We use an experimental design where roads are opened or closed to motorized traffic at specific times of year, and where motorized traffic has been quantified. We provide an environmental context to the study of the impacts of road closure on elk counts by accounting for climatic and vegetation changes over the course of the study. We specifically quantify the impact of road access, vegetation green-up, and snow dynamics on Rocky Mountain elk (Cervus canadensis nelsoni) counts along the main road in the Gros Ventre River drainage, WY, before and after two gates were sequentially opened to the public during the spring and early summer of 2010–2014. Elk counts increased with snow depth along the main road, and counts decreased as snow receded and vegetation greened over a 5-year period (p < 0.001). An increase in vehicle traffic resulted in a significant decline in elk counts (p < 0.001), which decreased at a rate of 1.42% for each unit increase in vehicle traffic. Our results indicate that gate closures in the Gros Ventre River Drainage decreased vehicle-related anthropogenic disturbance for elk, and that environmental variables affect elk counts and distribution further. Wildlife managers should consider both motorized vehicle traffic and the environmental context elk experience when managing road access in elk habitat.