Territorial behavior in dogs can lead to aggression, not only to the Dog's family but also to children and members of the public. This behavior can be an attempt by the Dog to establish its Pack Leadership over its Human Pack. This behavior is more likely to be exhibited in an entire male Dog than a female Dog although it sometimes does occur.
This behavior must be thwarted by one carer exhibiting Pack Leadership over the Dog's inappropriate aggressive and intimidating behavior, in a firm, educated and respectful manner.
Allowing the Dog to physically come up to our level when it is young, for example, getting up on the bed or lounge, is giving the Dog permission to be on the same psychological level as we are.
In Dog language, this is sending a message to the Dog that they can be equal, and if you like, the Pack Leader.
There are many Dogs, that by allowing them to share our beds and lounge will have no adverse effect on their behavior at all, but, to some, it is a clear message of approval of inappropriate and territorial behavior.
Many Dog owner/companions blame bad temperament for their Dogs unacceptable behavior. In most cases, this is merely a cop out for someone who is uneducated in Canine behavior and who is having problems educating and disciplining their Dog.
Steps to make sure this territorial behavior doesn't escalate and eventually become a threat if you have a Dog that is displaying territorial tendencies.
Establish an area within the bounds of the household that is solely for the Dog. A bed or chair that is only for the Dog is the ideal situation. Close enough to the Human Pack, so that the Dog does not feel isolated. Use this area for the Dogs bed, resting area and comfort zone.
Do not become complacent and allow the Dog to share your furniture.