I have a problem with my dog biting. Ill give little info on my situation. . Ive recently moved back home where my childhood dogs live ( an 11 year old retriever mix and 10 year old min poodle). While livingo n my own i got a border collie from the spca (3 years old). A few months back my collie bit the retriever infront of me, i disciplined her and she seemed to understand that it wasnt acceptable. we never had another problem until today when everyone was at work, i came home and the retriever had been bitten. i dont know how to correct the behavior because im not home when it happens. any advice??