A common problem on the fox-boards that new fox owners mention is that their kits play too rough and bite too hard during play. This is a very common problem in canines of any sort (domestic dogs included), so I figured I'd make a posting on how we broke Gizmo of it.
We had a bigger job teaching Gizmo to play gently than most new pet owners do, for the same reasons that we had an easier time socializing him. Because he was bottle-fed and raised away from his littermates, they weren't there to do the preliminary teaching on how to play nice, so when we got him he didn't have any of the starting bite-inhibition that most new puppies had.
We had to start from scratch.
With Gizmo, I first tried bitter apple to discourage rough play. ...Only to discover that he loved the taste of it, and I might as well have been trying to discourage him with BBQ sauce. To even phase him a little bit, I had to squirt a bit of it directly in his mouth, which I really wasn't comfortable with doing.
What seemed to work pretty well with him was yelping like a wounded litter-mate. Whenever he would bite down hard enough to cause pain, I'd let out a high-pitched yipe like I had been terribly wounded. On the first two or three nips, I let out a shrill yelp. After that, I would "scruff" him (grab him gently but firmly by the loose skin on the back of his neck), look him in the eye, and give him a short, sharp growl. Usually that would stop the too-rough play right there.
Scruffing isn't painful for them, and it's very similar to what a vixen in the skulk would do to correct a kit that's playing too rough. The goal here, both from the yelping and the scruffing, is to play to their natural social instincts.
If scruffing doesn't work, then I'd get up, walk off, and completely ignore him for five minutes. And ask any Gizmo, being ignored is the worst thing ever.
Something else we did when Gizmo was little was to used a sturdy oven-mitt to wrestle with him with. We'd "fight" with him with the mitt on, and then suddenly pull the mitt away and hide it behind our back with a firm but gentle "Stop.", and go to pet his ears with the other hand.
If he stopped being an "attack fox" and let us rub his ears, we said "Okay!" and the mitt came back and he got to fight with it some more. If he ignored the "Stop" command and went after the hand with no mitt, the game immediately ended, and I walked off and ignored him for a good five minutes.
He learned very quickly that to keep playing, he had to stop roughhousing when we told him to (I've always been impressed at how quickly he grasps things like this--much faster than any dog I've known.) Plus, the oven mitt gave him a very clear signal that "this is an okay thing for you to nom on when we play"--a shrill yelp whenever he happened to bite above it got him to focus his "attacks" only on the glove.
It was nice because with such a clear, visual signal that it was time to rough-house, we didn't have to worry about him spontaneously pouncing on and trying to nom on new people. We eventually phased out using the glove, but to start with it was a godsend. Not only was it a good learning tool for him, it helped up our confidence about our ability to handle him.
He's gotten pretty good about it, but I won't lie and say that this was 100% effective--if we're playing without the oven mitt, he still sometimes gets over-excited and nips too hard, but generally a yelp of pain from me is enough to get him minding his manners again.