I have a 2yr old german shepherd, ive had him since 12weks old. he is a GREAT dog. listens well, loves kids, other dogs, etc.... he is really the best dog ive had. so he is now 2, and we had our first child, she is now a month old... our shepherd now seems protective, which is expected, but now also seems irratable maybe? he is still the same loving dog to our family, but we have noticed him growling sometimes and showing his teeth on some ocations, to mainly strangers....its like hes not as friendly to introduce. is this cause the new baby? will it change? what should i do, do i punish him? even had a time a friend who he knows and seen a few times, started petting him, kind of rough, just to play a little, and he showed his teeth....he never used to do that..... thoughts anyone? thanks so much