HELP! 1.5YO M Neutered GSD POSSESSION AGGRESSION

[JLMooney14]

I am the owner of a young 1.5YO neutered male GSD dog named Kingston. I rescued Kingston on January 19th of 2012 from a young mother on Craigslist in NH. Kingston originally came from a breeder in NH. Although rambunctious and somewhat mouthy upon owning him, Kingston seemed to be a well-adjusted, happy puppy. I would take him to the dog park for hours on end where he would play and wrestle with both small and large dogs. However, his dominant and aggressive natured escalated as he got older, especially after he was neutered. Kingston is completely stable around adults and children. He knows basic commands such as sit, stay, paw, and can be walked off-leash. However, he has developed a severe case of possession aggression. Toys (Chuck-its, Balls, Frisbees), water and food are off limits to any dog. Kingston does not react if a human takes these objects away. However, if he is eating/drinking or playing with a toy and another dog approaches, he will immediately snap and bite the other canine. In addition, if he is mounted by another dog, the same will occur. Other than the possession aggression, he is rough with my smaller, 30LB Spaniel mix, will pull incessantly even with a pronged collar (especially towards a car he believes to me mine), and bark throughout the day at anything passing by an open window. I have tried to increase his level of exercise but his issues have not seemed to lessen. It has gotten to the point that he can no longer attend dog daycare/boarding, go to the park, or be around any dog with possessions nearby. I would hate to give Kingston up for adoption but am unsure of what to do from here. Any advice? Please let me know if you have any questions.

[Mary Beth]

If there is trainer in your area, I suggest you contact them. It does seem like Kingston has had some bad experiences like being mounted and that has triggered his dog aggressiveness. I would try to keep Kingston away from other dogs and use crates and gates inside the house so he is not in contact with your spaniel.

[WVGSD]

In the year that you have had Kingston, have you taken him to any structured training classes? It sounds like he needs some obedience training and perhaps even some changes at home such as "Nothing in Life is Free". You can Google this and learn how to change the rules at home and the pack structure to such a degree that you, the human, are the alpha.