Not all boy rabbits spray, and there really isn't a particular age when they start doing it. I've had some that weren't a problem with it, and others for whom it was like a hobby! There was one Jersey Wooly buck that I had, I had to make sure that everything that went on the grooming table before him was a buck. If he smelled doe smell on the mat, sure as shooting he'd write "Ziggie was here" across the front of my shirt! I remember one Holland buck that seemed to take delight in spritzing me when I came around with the feed bucket. He did grow out of it, finally. Young bucks are worse about it; I usually put my young males in cages that are closer to the ground just to make sure they can't shoot me in the eye.
The gender confusion is so common, rabbit breeders have a joke about getting visited by the "sex change fairy." And though a good eye and experience helps one make fewer mistakes, I have seen some very, very experienced rabbit breeders getting razzed for putting a young buck in a young doe class (all in good fun, of course, 'cause we've all done it)!
