although there hasn't been an incident t since we returned home from summer vacation the end of July, there was one yesterday in the yard. I have 7 fenced in acres,,had let them out together( I have a 3rd male Rottie mix) because they were mildly barking at some far off critter. I held Gracie back,,as I always do so Roma wouldn't feel threatened , and let them all out . They branched out separately like they always do. I got on a phone call so wasn't paying attention to them, couldn't have seen them anyway from the house with the trees. 15 minutes later, they all came back, roma and Pancho went straight into the pool, Gracie was the last to appear, covered in dirt and mud( we have a baseball field in our yar and it had just rained). The others weren't dirty, just panting more than usual but figured it was from chasing a squirrel or rough housing with each other. gracie was panting the most, I hosed her off, then noticed a couple punctures around her neck. I took her inside and examined her further,,she had a very raw bruised neck, a dime sized hole in the side of her neck, and multiple punctures. I called the vet who,happened to be open late last night, took her in, where they shaved all her spots and closed the big one with 4 staples! This is the second time she has required staples from Roma. Since I didn't see it happen, my guess is they had a squirrel treed way back in the yard, and roma was frenzying over it( she has been lucky to,catch one twice that fell after failing to make the leap to,a better tree) and she saw gracie as a threat. I don't know if the male got into it, I doubt it, because he usually just stands there when the females go at it. gracie never starts it nor fights back. I am just sick about it. I had been so good about supervising them, and they were getting along fine, seemed to really love each other. My dilemma is, I have had Roma since she was a puppy, came from the rescue I am very involved in, and her sister Gracie,,was returned to the rescue at 18 months, I fostered her,,and adopted her. I was thinking if anyone has to be rehomed it would be Gracie, since she came late. My husband adores her and is mad at Roma. My male, Pancho is very bonded to Roma, tolerates Gracie, is just starting to almost like her. I have asked for the advice of a trainer, she basically,says it is instinctual for Roma to want to eliminate Gracie when prey is involved. Since the incidents are so rare, it would be impossible to set it up, and correct Roma If she is going to attack. I am also talking with the president of the rescue about what the best solution is. I love them both, and Gracie had some trust issues when she came to me, I worked so hard with her to prepare her for adoption, then ended up not being able to give her up. Advice please?