FWIW, from Field and Stream:
Not quite sure if the track you're on belongs to a buck or doe? Look for yellow snow. Does stop and squat to urinate, leaving their mark behind an imaginary line connecting the back of the rear hoof prints. Bucks often whiz on the move, dribbling urine as they go. When a buck does stop to urinate, he shoots a yellow hole into the snow a little forward of that line. Bucks are also more likely than does to defecate on the run, leaving a line of pellets. –B.V.