My sister's German Shepherd dog had puppies almost 2 years ago (my sister has both parents). She has both parents, and 3 of the pups (1 male, 2 female) living at her house - one of the female pups is mine, but currently I am not able to have my pup live with me, and yes my "pup" is almost 2 and i still refer to her as a "pup". Every chance I have, I am at my sisters to spend time, train and play with my pup. Sometimes I am able to take the other 2 pups outside to play with us and sometimes I am able to get the parents out as well. Ever since the pups were a few months old, the mother would periodically attack my pup. Thankfully, there has not been any serious injuries. The mother has attacked the male pup once and left a scar under his one eye, and also attacked the other female once or twice as well. It is only my pup that the mother attacks most often.
My sister thought my pup gets attacked because she is very energetic and more excitable than the other 2 pups. The number of attacks has decreased, but the most recent ones were completely unprovoked. My pup would just walk in the living room from another room and the mother would attack. I took my pup to a park to play for a bit and when I brought her home, the other dogs were happy to see her and were sniffing her. My pup laid on her back in a submissive position and when the mother dog came over, she attacked my pup. I was right there at the time, so i was able to grab the mother dog to keep her from biting at my pup more than she already had. Again, skin was not broken, but the fur on my pup's throat was wet where the mother had tried to bite at. I also would like to mention that my pup has never tried to fight back. Once she is able to, she runs and hides from the mother dog, then tries to avoid being in the same room as the mother for several days after.
My sister and I both have asked several trainers about the mother dog doing this to just one pup and no one can explain why she may be doing this. Four of the five dogs are spayed/neutered only the male pup is not neutered. The mother dog is the dominate one (obviously) and my pup does not try to challenge her in any way. I was told that dogs do not wait to get "even" with another dog should the other dog do something the first dog did not like. Since I cannot live with my pup right now and I shower her with attention when I am with her, is possible that the mother dog could be jealous and would attack out of jealousy? Even with that said, there are times when no human is around my pup and she is just chewing on a toy or just laying down with nothing hear her and she gets attacked. So it is difficult to say what sets off the mother to make her attack.
Does anyone have any ideas? Like I said, I have asked several trainers and have even mentioned it to my vet and no one is able to give a reason. Thank you.