I understand your fears. Yes some pits are fine, but any large dog coming at a yorkie is like
It would be the same if we took our yorkies into a room that some one had their pet mice or rats running around you just would not do it. Not all yorkies will kill a rat but you just don't know. To me it's the same thing (size difference is about the same too) Yes I agree with others you need to talk to the new neighbours
