I was looking for a Guardian breed and looked at the Cane Corso, American Bulldog, Dogue de Bordeaux,and then i found out about the Presa. I had gotten my female Bordeaux and wanted a much more serious dog, witch is how i chose the Presa of course. I had done a lot of homework before the decision, and then found a local breeder here who has outstanding bloodlines and takes great care of his dogs. We ended up being great friends too. I get to help at the kennels, train the dogs, its a good time. My boy does not tolerate other males either, and has also growled and circled people who ive let in the house, but that is not allowed of course, once I make a decision to let someone in, he needs to accept it. That is all recent, but can be expected since he is getting into that young adult stage. Very serious dog, not for the beginner or even intermediate dog owner. i am glad you had made the decision to fix your dogs, very smart of you.