AN EVALUATION OF SNOW-URINE RATIOS AS INDEXES OF UNGULATE NUTRITIONAL-STATUS

We monitored trends in urea nitrogen : creatinine (UN:C), cortisol:cre atinine (Co:C), and allantoin:creatinine (A:C) ratios of snow-urine sa mples from 5 free-ranging female elk (Cervus elaphus) in Yellowstone N ational Park over a three-winter period to determine their potential a s indices of nutrition or nutritional stress. UN:C ratios indicated th at elk were nutritionally deprived during winter, but values did not v ary significantly among winters despite interannual differences in win ter severity inferred from snowpack measurements and declines in calf: cow ratios. The UN:C ratio appears to be an insensitive indicator of n utritional stress over a wide range of nutritional conditions. Co:C ra tios demonstrated a significantly different linear trend during each w inter, but we were unable to interpret these trends because they were hot related to interannual differences in indices of nutritional stres s. A:C ratios demonstrated a consistent, seasonal, parabolic pattern o f nutrition, with lower values occurring in midwinter and higher value s in December and April. There was also a significant year effect, wit h lower values occurring during the hardest winter and higher values d uring the mildest winter. Hence, trends in A:C ratios were sensitive, interpretable, and consistent with variations in winter severity and d igestible energy intake, suggesting that this metabolite warrants furt her scrutiny.