PHYSIOLOGICAL ASSESSMENT OF WINTER NUTRITIONAL DEPRIVATION IN ELK OF YELLOWSTONE-NATIONAL-PARK

During 13 January-29 March 1988, we assessed the extent of nutritional deprivation in cow elk (Cervus elaphus nelsoni) groups on the lower, middle, and upper Northern Range and on the Madison-Firehole Range in Yellowstone National Park by 4 sequential collections and chemical analyses of urine excreted in snow (snow-urine). Associated changes in elk density and calf : cow ratios also were estimated during early and late winter or spring. Decreasing (P = 0.0001) potassium: creatinine (K:C) ratios throughout winter and increased (P = 0.0001) urea nitrogen: creatinine (U:C) on all 4 areas indicated progressive nutritional deprivation and increasing net catabolism of lean body tissue, respectively. These ratios also varied among the 4 sampling areas during early (P = 0.0001) and late winter (P < 0.005). Low sodium: creatinine (Na:C) indicated low sodium availability on the Northern and Madison-Firehole Ranges throughout winter. Comparison of U:C and K:C data to those of supplementally fed captive elk and winter-killed elk permitted classification of the physiological status of Yellowstone elk relative to nutritional deprivation. Nutritional deprivation of elk across the Northern Range and at Madison-Firehole was associated- with significant (P < 0.05) declines in calf : cow ratios from early to late winter. Throughout winter, snow-urine samples with metabolite profiles indicative of severe energy deprivation and accelerated degradation of lean body tissue were most apparent in areas associated with increased elk density and/or deep snow cover.