Fecal indicators of nutritional status of wild ungulates are less cons
trained than blood or urine analyses. Thus, we assessed the potential
for fecal nitrogen concentration to predict winter dietary quality for
Rocky Mountain bighorn sheep (Ovis canadensis) in Wyoming. Dietary ni
trogen concentration and percent in vitro dry matter digestibility inc
reased linearly with increases in fecal nitrogen concentration for han
d-plucked diets of wild sheep on 4 winter ranges and for tannin-free d
iets fed to 3 penned adult female bighorn sheep (2 were 1/8 mouflon [O
. orientalis]). A linear regression developed from field samples gathe
red in 2 winters accurately predicted winter dietary nitrogen concentr
ations using fecal nitrogen levels from other winters. Fecal nitrogen
concentrations differed (P < 0.0001) among 7 winter ranges. Our data s
uggest that fecal nitrogen concentrations < 1.3% may identify winter d
iets that are deficient in protein and energy for bighorn sheep.