Resource Partitioning and Dietary Overlap of Mule Deer and Elk in Eastern Nevada
AdvisorWeisberg, Peter J
Natural Resources and Environmental Science
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In semi-arid environments, such as the Great Basin, low productivity and frequent drought conditions increase the complexity of understanding the potential for competition, habitat selection, and dietary separation between native ungulates and cattle. I studied resource partitioning and spatial patterns of habitat use by female mule deer (Odocoileus hemionus) and female elk (Cervus elaphus) in eastern Nevada during winter, spring, and summer. I also examined dietary composition and overlap of mule deer, elk, and cattle. To assess resource partitioning and spatial distributions I used ecological niche factor analysis (ENFA) to analyze the areas used by radio-collared mule deer and elk and create habitat suitability maps for both species. I found that both species were using habitats close to dirt roads and that areas with high pinyon-juniper cover were avoided during all seasons. Nonetheless, there was selection for low-density pinyon-juniper areas and areas in proximity to pinyon-juniper. Mule deer selected for specific elevational ranges (2300m to 2500m) and areas close to springs during the summer. Elk selected for higher elevations during spring and summer. Slope and proximity to springs were also important during summer. I found that habitat use was more restricted during summer than for the other seasons for both species, but especially mule deer. My results suggest that in these semi-arid watersheds, mule deer and elk may be more restricted by availability of water and high quality forage during summer. To assess dietary composition and overlap between mule deer, elk, and cattle, diet utilization was quantified from microhistological analysis of rumen and fecal samples. I observed that that there was not substantial dietary overlap among elk and mule deer from October to December, but that dietary overlap was greatest in summer. Elk and mule deer showed greater dietary overlap than elk and cattle. I observed a slight dietary separation among male and female elk, with female elk diets having a greater graminoid component than male elk. Elk and cattle exhibited greater dietary separation in my study area that included a crested wheatgrass seeding, suggesting either that elk avoided areas of high cattle concentration (i.e. crested wheatgrass seedings), or that cattle preferred the seeded grasses and utilized less of other forage species favored by elk.