Redirected aggression maybe.
I had a couple of bitches at my place that would have killed each other. They would fence fight, down and up, and after coming away from the fence, the one would grab a squeeky toy and squeek and shake the heck out of it. Once she grabbed a young male pup -- not hers. I was right there and she let go immedieately, but at that point I realized the fence fighting had to stop and put up a large tarp so they could not make faces at each other.
I think it was misplaced or re-directed aggression.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC