I have a 2.5 year old small crossbreed (pug, chihuahua and assorted terrier according to his DNA results).
He is extremely alert and responds very angrily to any sound or sight of a stranger (or strange dog) approaching his home. It is a very instinctive response, when he sees or hears anything he will leap up (even when very relaxed), run to the window, stand up to peer out and shout very loudly about the situation.
I obviously lock him up when deliveries come but there have been a few slip ups (not for a long time now as I have learnt my lesson!) and when this has happened he has "gone for" people though never actually bitten, just sort of air snapped/nipped. I don't think he would hurt anybody and he is a smallish dog but I obviously would like to do anything I can to mitigate the risk further. If I take him on the street outside the house he will also try and lunge at anyone walking past but only ever on our street. Outside of our "territory" he is very friendly.
I understand that he will have learnt that his behaviour "works", in that he barks at people walking past and then they go away so it has constantly been reinforced. I have trained him to stop barking/ come back from the window when I ask but can't work out how to crack the stopping him having the instinct to do it in the first place. It seems very deeply ingrained. Has anybody had this issue and successfully squashed the guard dog instinct?
In an ideal world I would recruit lots of friendly strangers to walk past the house and ring the doorbell and then not leave and to use positive reinforcement to change his associations but in the real world I know no one he doesn't know and have no means of recruiting strangers! What are my other options?