I have a four month old Patterdale terrier called Nigel who is very boisterous and confident He has been really good up until late. The problem occurred when we started giving him pigs ears to chew in his bed. When he has one and we enter the room he starts to growl out of character. Then when I take it from him he gets really vicious and bites and I mean really vicious. I have never seen a dog do this. When this has happened I have grabbed him by the scruff of the neck and slapped him on the top of his hind legs, took everything away from him and paid him no attention (not sure if I am correct in doing this). From when we had him we have taken toys from him to try an avoid situations like this in case it happens with a kid. At night we keep him in a large cage and he is great. On walks he is good with other dogs and other people. I would be grateful if anyone could offer advice on how to resolve this. Thanks in advance.