Aggressive Aussie

Question
I have a 5 year old Aussie neutered male and have done a ton of training w/ him, positive reinforcement/some clicker/tricks etc.  Very motivated and quick learner.  However, he barks intensely and nips/bumps certain people - mainly young men (all my sons' male friends) and my father in law (in my apartment only - not at his house any longer - we worked that out w/ peanut butter :-)), men with hats, black men.  Has nipped a few of people through their pants and broken skin.  Fine with women.  Fine with most adult men who come in my NYC apartment, as long as I crate him when the bell rings and let him out only after he's lying down in the crate and the person is in the living room.  I can't keep making excuses or relying on "management" - have to work harder to reduce his fears.  Was thinking about gradual classical conditioning using a muzzle.  Any thoughts?

Answer
I think that's a fine idea as long as you don't get your hopes up that it will work in all situations - there may always be that one instance of a novel stimulus that will trigger a poke, even if you think you've worked hard on most of the situations he will be expected to encounter at home.  Just remember to acclimate him to the muzzle gradually before you begin to work with him.  There's a nice article on www.morrco.com about how to do that, and I like the muzzles they sell, too.  Avoid the metal ones with an Aussie that "pokes", as the metal muzzle can hurt the "victim" almost as much as a nip.  I would use a basket muzzle and use squeeze cheese as the reinforcement, since you can poke the nozzle through the muzzle or put some in using your fingertip.  If you use a cloth muzzle, it's easier to reward the dog, but I find that most Aussies can still deliver a nip with one on, so that would just be for leashed work at a distance from the "scary thing".  

The good thing about muzzle work is that YOU relax more, too, which means that your fear is not feeding into the dog's anxiety.  Do have your dog's thyroid levels checked, too, as some dogs exhibit aggressive behavior if that's out of whack.  It may not eliminate the problem, but it's better to know, and treat, just in case.  (Have the vet send the sample to Michigan - Google on "Dr. Jean Dodds" to see why.)  

You may be able to make this better, but, sadly, there are some dogs that do require lifelong management.  But, muzzle acclimation can enable you to have company or be in public without fear of a lawsuit!  The muzzled dog is the safest dog on the block, so don't be afraid to have your dog wear one whenever he's in the company of men.  Just make him love that muzzle first!!!:-))