At what point does territorial behavior tend to begin?
I'm confused on how to "diagnose" my dog on this.
Bailey can easily see through the house windows that face the driveway. If anyone drives up, he's barking. (It's a long gravel drive, it's easy to hear the gravel crunch, easy to see the headlights -- no one just randomly drives up my driveway.) If he sees someone walking down the road, he's barking. (This rarey happens, as the road is far off, but occasionally does occur.) If we're outside and a car pulls up the drive, he's on alert and barking. (By on alert, I mean, wide stance, tail up, ears up, no hackles up.)
This behavior only occurs at the house. For example, I often run into the convenience store and leave him in the car. He just sits there. He isn't frantic, he doesn't bark, he does nothing... but just sit there and look around. Granted, no one has ever approached the car that I am aware of, and I'm often looking out at him as I'm in the store, but he is really the picture of calm in the car.
What's going on?