All 3 of mine bark at Strangers and they also growl at the same time. But I only Trained my female Abigail to do it. My other 2, the male Artie and Tiffany, their
baby that is only 8 months old only go into "Guard Dog" or Attack mode when she does, she's the Instigator! She gets them excited, they will also do it on command......"Look who's that"? or "What's that"? Our backyard is not fenced in
and we live right next door to the DogPark. There is alot of car and foot traffic all around our house so I don't mind when they do it naturally, in fact I feel pretty safe knowing they are alert!