Dogs often display some form of aggression to some degree, this is entirely natural. Even so, as our dogs are domesticated pets, a certain level calm is to be expected.
Territorial aggression is the most common of the aggression behaviour problems – this refers to a dog that goes entirely crazy should a stranger approach their home. A dog has a natural instinct to defend its home and to mark their territory.
Here are several scenarios that might result in a dog's aggression to escalate –
[1] Aggression in a dog can be reinforced in the following situation – a courier approaches the property to leave a parcel, once dropping off that parcel he leaves. A dog might think that he drove that stranger off and this itself can result in more aggression.
[2] If riding in a vehicle, a dog with territorial aggression that's extreme often barks ceaselessly at every moving object going by. Of course, as no one is going to approach the vehicle, the dog believes he is winning.
[3] If a dog is barking at the front door (for any reason) and their owner shouts to shut him up – this can increase the level of aggression. Dog owners don’t realize that shouting at a pet is doing nothing more than to create more aggression. A dog might believe that yelling is supporting his aggressive behavior towards a delivery person or stranger.
[4] If locked up or isolated when strangers or guests are in the house – this can result in a heightened level of territorial aggression. Often able to smell the presence of an intruder, but unable to do anything due to be shut in. This can cause anxiety and stress, which leads to on to further behavioural problems.