I have a Boxer mix that probably has some Pit Bull in it. He was a stray and I adopted him around 2 months ago and he is probably around 2 years old. He has met children 2-6 years old and we have a cat in the house and he has shown no aggression. He is nervous around men at first when they enter the house but warms up to them quickly and is very affectionate with people. He is fixed.

I've been bringing him to a local off-leash area and he plays very well with the other dogs and shows no aggression toward dogs-rarely even barks. Recently there were a couple very bad fights between other dogs (both times pit bull mixes that shouldn't be in a leash free zone). When the fights start my dog will jump at the nearest human and bark at them aggressively. It's the only time I've seen him show any type of aggressive behavior (he does want to chase squirrels and rabbits but I'm not sure if that is considered aggression).

I spoke with a friend who is a Vet and he says this is not that uncommon in some dogs and didn't think there was much you could do about it. I've stopped taking him to that park for the time being because these other aggressive dogs/irresponsible owners are putting mine in a bad situation. I was just wondering if anyone had any similar experience and if they had any thoughts.

I don't see a problem. Too bad the others are causing trouble. I hope the dog park clears up the problem and you can go back soon. In the mean time, work on your leadership with him. The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at Raising Your Dog with the Monks of New Skete For more on being top dog, see Establishing and Keeping Alpha Position, Letting your dog know you are the boss

Thank you for giving him a home. We need millions more of you.

He is a gorgeous dog. It's really is a shame that there are people out there that are irresponsible enough to bring their aggressive dogs to public dog parks like that. More than likely it is just that type of situation that makes him nervous as it doesn't sound like he is aggressive normally. Labmans advice on leadership will help to control his behavior in less than ideal situations like that should they arise. Otherwise, I think you're a wonderful person to give him a good home, and he seems like a sweetheart. The picture with the cat is so cute. If he's fine with the cat then I'll bet the squirrel and rabbit chasing is out of pure excitement:)

Well this is quite a problem for your dog and you make sure the dog knows who's boss or else he will push you around like your not leading him and other dogs will attack him and he will do so