I imported a dog 5 years ago from a reputable breeder in Slovakia. It is a small kennel and the dogs receive a good deal of attention from the breeder and his family. They also do some foundational schutzhund work so the are obedient and have great starting bite work. My guy (Wolfgang) has been a gem since day one. Very stable around kids and other dogs. All he cares about is being close to me and my family and the ever important ball. He has always barked during any protection work and will bark on command but for the past 5 years he has never once barked outside of those conditions. Not at the door bell, the mailman, other dogs barking at him, not a peep. I was at first disappointed as part of having a GSD is the security of that nice loud and deep bark when someone comes on to your property. After a few years I got use to the fact he would not bark even at a stranger entering the house. He would stop them with an intense stare that meant business, but not a single woof. A few months ago, now into his 5th year with us and all environmental conditions being the same, he started "alarm" barking. If someone is near or on the property when we are in the house. He doesn't go crazy, he lets loose a short cycle of some very authoritative barks and stops when I tell him. Over the past months this has been consistent. Not barking to much but just enough to alert us and others he is protecting. I have to say I like the change. I have no idea why it came about but it came on in the perfect dose. I feel for those who have barkers that are excessive. I have hope for those with a non barker that even an old dog can teach himself a new trick. BTW he is quite pleased with himself about the situation and once he short volley is over he turns to me and give that " I did good look".