It's been a really long time, my GSD is going to be 5 years old in 2 months.
I can't recall when he started barking at noises but he was 16 months old when he showed real protectiveness and made these 2 crackheads back away from us. He really stepped up and became a guard dog when he was 4 years old. When he is out in the yard he makes sure everyone knows that he is there and that it is his yard. He puts on a really good show and people that don't know him are scared of him but he is actually a total sweetheart and great with people.
My Dalmatian puppy started barking around 5 months of age but when he is out in the yard he would kind of stay back and bark, now he stands next to Sinister and barks/raises his hair and acts like he would do something but again, he is extremely sweet and great with people.
Sinister ~ 5 yr old black male GSD 3.11.09
Draco ~ 9 mth old male Dalmatian 6.30.13