Victoria Patrek

Master Thesis:
Fat but not happy: The Effects of Supplemental Feeding on Stress Hormone Levels in Elk

On 23 feedgrounds in Wyoming, elk (Cervus elaphus) are provided with supplemental feed throughout the winter by state and federal agencies. Brucellosis seroprevalence of feedground elk is 26% whereas other elk in the Greater Yellowstone Ecosystem display a seroprevalence of only 2-3%. The aggregation of elk during the peak transmission period of brucellosis sustains the high seroprevalence observed in fed populations. It is clear that feedgrounds provide an ideal setting for the transmission and persistence of disease; however little is know about physiological responses of elk to supplemental feeding. The conditions on feedgrounds present elk with stressors not present on native winter range, and chronically high stress hormone levels are known to suppress the immune system. In this study we investigate how supplemental feeding affects stress hormone levels in elk. We found that elk on feedgrounds had significantly higher stress hormone levels than unfed elk. We also experimentally manipulated feeding density to see if management practices could reduce stress hormone levels. Reduction of feeding density did not have a significant effect on stress hormone levels, but group size and feedground density were correlated with stress hormone levels. The results of this study indicate that higher stress hormone levels on feedgrounds may play a role in the disease dynamics.

Publications
Cross, PC, J Drewe, V Patrek, G Pearce, MD Samuel & RJ Delahay. In press. Host population structure and implications for disease management. In RJ Delahay, GC Smith, & MR Hutchings (eds.) Management of Disease in Wild Mammals. Springer-Verlag Tokyo, Inc. Tokyo