Tubby is my watch cat too. Quite often I will see him sitting by the long window that is next to the front door - surveying his territory, as I like to call it. If he sees someone walking in the street or a yard guy or something, he will start growling too. It was so funny the first time Terry heard him do that, because Terry didn't know that cats growl. He thought something was wrong with Tubby.

However, I have to note that as soon as the "invader" comes in the door, all growling is abandoned and rubbing up against and begging for pets is the new "protection" offered. Unfortunately I think if anyone ever broke in the house, Tubby would just follow them around looking for pets as they walked away with the house.