Your Question: My ~3yr old Pit Bull attacked my 13yr old border collie (the queen dog). After a new small terrier had been introduced to the family, (with us for 2 months, and had become a playmate with the PB). The border collie barked at the little terrier. How do I go about defusing the dog-dog issue? Can I get it back to the more neutral situation?
Thanks for your inquiry. This is a very complex issue and has to do with pack/rank dynamics that can be tricky to sort out. If a younger dog is going after the older one it may be a sign that she's taking over. Adding a third dog may have thrown the entire pack structure up in the air and everyone is testing now. The thing is, you have to be perceived by all dogs as the leader, which would put you in the position to control the conflict in the group. If this is not unequivocally the case, it needs to be. Then we also have to sort out which of the dogs is the natural leader and reinforce that dog in its hierarchically appropriate position with preferential treatment that is apparent to all dogs. At the same time, if you've established yourself as leader you should be in a position to reprimand lower ranking pack members for inappropriate overtures and posturing towards more dominant dogs and also reprimand the more dominant dogs for any bullying behaviors.
Anyway, like I said, it's complex. If you end up with more fights you should get professional help asap!