PHYSIOLOGICAL-RESPONSES OF YELLOWSTONE BISON TO WINTER NUTRITIONAL DEPRIVATION

Because nutrition is critically related to other aspects of bison (Bis on bison) ecology, and the winter ranges inhabited by bison in Yellows tone National Park (YNP) are ecologically diverse, it was important to determine if nutritional deprivation differences occurred among winte r ranges. We used chemistry profiles of urine suspended in snow to com pare nutritional deprivation of bison from january to April 1988 on 4 sampling areas of 3 winter ranges in YNP. Declining (P < 0.001) trends of urinary potassium: creatinine ratios in bison on all 4 sampling ar eas indicated progressive nutritional deprivation through late March. Concurrent increases (P less-than-or-equal-to 0.001) in mean urea nitr ogen: creatinine ratios from late February through late March in 3 of 4 areas suggested that increased net catabolism was occurring. Diminis hed creatinine ratios of sodium and phosphorus reflected low dietary i ntake of these minerals throughout winter. Mean values and trends Of U rinary characteristics indicated nutritional deprivation varied among 3 winter ranges in YNP. Continued physiological monitoring of nutritio nal deprivation, along with detailed examination of other aspects of t he bison's ecology, will provide greater insight into the role of ungu late nutrition in the dynamics of such a complex system and improve ma nagement.