If you stated that is happened almost immediately after you added the other JD, I highly DOUBT they were getting ready to breed.
My Jag and RT do this (but only for maybe a minute- then the RT retreats), and they are both males.. def not trying to breed there.
LOL you totally missed the joke that the people who said they where trying to breed where idoits.
The piss poor owners that shouldn't be keeping pits or any other large dogs are the ones keeping the bad rep going, maybe focus your attention towards stopping them. Offended 