9th International Deer Biology Congress

AUTHORS: Matthew M. Hayes and Kevin L. Monteith – Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology, University of Wyoming and Haub School of Environment and Natural Resources

ABSTRACT: Throughout the western United States, mule deer and elk populations have been in a state of flux for the past century. Following overharvest during the westward expansion and colonization of the continent, populations of these species have recovered from historic lows, but more recently, researchers and managers have struggled to understand their disparate population trajectories. While elk populations have been increasing and are regulated largely by female harvest, mule deer populations have declined or been stagnant, despite minimal or non-existent female harvest and millions of dollars invested in recovery efforts. Researchers and managers have studied the dynamics at play between mule deer and elk populations, however that work often was independently focused on a single species as opposed to how their sympatric existence may affect each other. In an effort to quantify the potential for direct competition between mule deer and elk, our ongoing research is focused on understanding how shifting movement patterns, and habitat use affect these two species, and whether direct competition causes constraints on individual performance. To examine potential direct competition, we are using fitness-based metrics measured in the spring and fall of each year, coupled with movement patterns and habitat selection of these sympatric ungulates in a typical high-desert ecosystem in western Wyoming. We hypothesize that when mule deer and elk move into close contact with each other in both temporal and spatial dimensions, that mule deer will respond by shifting their patterns of movement and habitat use while elk will show no discernible alterations to movement or habitat use. If mule deer are altering their behavior in the presence of elk, we further expect that there will be decreases in fitness-based metrics for mule deer with little or no change in elk fitness metrics. Our continuing work will elucidate the degree to which direct competition and niche partitioning are structuring mule deer and elk populations through fitness-based metrics. Our results will have profound implications for the management and conservation of these iconic species and may lend insight into their disparate population trajectories.