I have a male lab mix that is almost two years old. I got him when he was three months and he was already neutered. It is likely that part of his mix is with pit bull as most of the other dogs at the shelter I got him at were. He has a problem with spontaneous bouts of aggression towards other dogs. Let me start by saying he seems to love other dogs he gets incredibly excited to play with any other dog. Whines if he is somewhere where he can see another dog and not play with them, never barks or growls as he is approaching other dogs on leash etc. He usually plays for awhile doing normal acceptable behavior chase some light wrestling etc. Eventually however he'll become interested in toys, which I have now completely taken away because they cause problems. This play usually takes place outside though so he will find literally any object a stick, a piece of bark, clump of grass, you name it and he'll treat it as a desirable object. Then the problems start if he ever relinquishes this object and the other dog even trots over to smell it he comes barreling back growling and getting aggressive wrestling bitting. If hes holding onto the object and the other dog finds his own or even seems to be poking around in the dirt or by the fence at something that could be a similar object same story. Sometime when hes been playing for a while with dogs and they are all tired and just lying around he will go get an object and just plop it down within distance of the other dogs and lay down slightly removed from it and wait for one of the dogs to even come in the direction of it and same story aggression. The behavior is particularly frustrating because he seems to be obsessed with other dogs and want to play with them so badly and does for a while but will eventually exhibit this behavior. He is never aggressive towards humans beyond the normal someones at the door bark/growl until I see who it is even if its someone I don't know and hes happy. I can feed him and approach and pet him as he eat etc. I will say that this behavior normally takes place in his own yard which makes it slightly more understandable but still unacceptable. He still does similar things when we go to public dog parks though. Many of the dogs that come to play hes known for over a year now is still ecstatic to see them but eventually gets aggressive. Most of what I've read seems to say that this is an instinctive behavior and there is little you can do and merely suggest for this particular dog no toys or objects which is essentially impossible in a big backyard or just not letting him interact with other dogs. I don't like this solution for many reason and was hoping for some advice on how to curb this behavior what to do when he does do this etc. Thanks in advance sorry for the long post.