Bitter Apple works by tasting *BAD*! The problem with spraying directly in/on a ferret is that it is very potent and provokes a very strong negative reaction. I once used it directly to separate 2 hobs who had broken out of their cages and were determined to do each other in. The reaction was quite unpleasant to watch, and I would never do it except to prevent serious harm. Also, spraying could get it in their eyes, which would be very painful. I had much better luck teaching a biter that ferret necks don't taste so good by first spraying a bit on my fingers, then petting the back of the bitee's neck. This allows you to control how much the fuzzy is getting and where. The biter gave up after a week or so. Good luck! Rob McNish and the Gang at McFerret Acres [Posted in FML issue 1946]