ENERGY REQUIREMENTS OF MULE DEER FAWNS IN WINTER

Maintenance energy requirement of tame mule deer (Odocoileus hemionus hemionus) fawns of similar age and body weight was determined under winter conditions in north central Colorado by subjecting test groups to 4 levels of energy intake. Twenty-five digestion trials were carried out to evaluate the experimental diet in 2 winters. In the 1st winter 3 lots of fawns were used. The 1st was fed ad libitum, the second 75% and third 50% of the pretreatment ad libitum intake. In the 2nd winter one lot was fed ad libitum and another was fed 25% of ad libitum. A linear regression of metabolizable energy intake and corresponding body weight gain or loss indicated that the maintenance requirement was.158 kcal of metabolizable energy per WUO.'Vday in 2 winters of study. J. WILDL. MANAGE. 43(1):162-169 Energy requirements of wild rumi- nants in their natural environment are poorly understood. Quantitative deter- mination of range carrying capacity for deer is dependent on knowledge of sea- sonal energy needs and seasonal supplies of energy in range forage. With mule deer this knowledge is especially critical in areas with cold winter climates. Heat conservation and compensatory adjust- ment of caloric intake in relation to cold stress are important factors in determin- ing the capacity of forage to maintain deer.