
One thing to remember is that Rotts tend to be quite 'talkative', so is it definatly 'growling?
had a girl who would mutter and mumble at loads of things - as in -hurry up and put my dish down, make a fuss of me, he (GSD) has pinched my toy etc.
Took her to Suffolk show one year and she did a meet and greet with various people - both known and not, quite a few said 'oh is she growling

' However one guy who knew Rotts was chuffed to bits 'Oh she's talking to me!!!'
Had/got total of 3 GSD and 3 Xbreed ( Cocker/Lab, Pointer/whippet & Stafford/?hound) and none of them ever made similar noises in the same situations.