My rottweiler is 7 years old and has been living with us all his life and just as recently as today, My father would call him over and he would reach his hand out to pet him and the dog will just start growling at him and slowly backing away like he is some kind of stranger or something. He even tried to nip a few times and I'd say my father is the master. It's like a sudden behavior change because he would call him over and be able to pet him all the time and now he will just completely ignore the call, stare at him and pant or growl over and over again. He looks nervous or something. I try the same with me and he comes over to lick my hand, ect... Like normal. My father has never done anything to scare or hurt him in any way. He is scaring me with this strange behavior. Does he sense that something is wrong with my father? Did he have a bad dream about my father? Is my dog going senial? I am very confused. Has anyone experienced anything similar or has knowledge of this behavior ?