Setting aside any medical reason for the problem
What you are dealing with is "Resource Guarding."
Resource guarding is a natural dog function. Not wanted but normal. Think of a dog scavenging for food, his survival depends on retaining food.
This is also a largely self rewarding behavior. Dog growls people/dogs back off dog is rewarded even if the encroachment is only temporarily thwarted.
If the techniques are working then the growling and threats should be less prevelent now then when you start.
We are working through this problem applying firm discipline (using techniques from the Dog Whisperer). The techniques are working, we are committed to fixing this problem,
If not the techniqes are not working. There are some real problems with trying to solve this problem with force.
1. the tough (personality) dog learn ye who applies the most force wins not a good thing.
2. the soft (personality) dog learns growl and threatening leads to punishment it wants to avoid so it stops threatening and growling. Great you would think! Not really the desire to retain the object has not changed. It is not uncommon for such a dog to skip through that ritualistic dispay meant to thwart any attempt to take the object and jump right to biting without warning. I have aquired such a dog through rescue and had to reteach her to grow and such because that is far safer than a dog who bites first.
1. If all you had was dog - dog aggression I would say what's the big deal. Unless the incidents were increasing in frequency and/or intensity I would not be that concerned. The other thing to keep in mind is rarely does this behavior come out of the food. Unless the dog was given a reason to now guard its food. One must consider the dynamics of the whole situation, Is blame to be placed on the dog who growls to protect his or the dog that is pressuring him to give it up? When it comes to dog-dog aggression it takes two to tango and you can't let one off the hook.
2. Dog - human agression is a different mattter. There become a much larger liability issue. The basic concept to change an aggressive behavior is to change the dogs perpective on what is likely to happen when a human approaches him when he has food. If the dog feels the nedd to guard it is likely he feels the human is a threat to take his food. If on the onther hand if the dog thought the approach of a human even though he had food was to give him something even better he is less likely to be defensive.
Getting into detailed steps on how to accomplish this no in the scope of the limited space of this forum. Also because factors that can't be known unless observed it is alway best to consult with a hands on behaviorist to help you through the problem. Any online, fax etc help is capable of beinging seriously hampered because it is reling on your input. Often being part of the dynamic involved you miss or missinterpret key aspects of the situation which can severely hinder a sucessful out come.
Some resource you may want to investigate
FIGHT! A PRACTICAL GUIDE TO THE TREATMENT OF DOG-DOG AGGRESSION
by Jean Donaldson has chapters devoted to dealing with dog - dog resource guarding.
MINE! A GUIDE TO RESOURCE GUARDING IN DOGS
by Jean Donaldson deals with resource guard by dogs from humans
Food Bowl Exercises
includes rehab exercises
book review of both books recommended above
Book Review Fight! by Jean Donaldson
"Written for the dog trainer or well-read dog owner, Fight! "is about dogs who fight with, lunge at and don't get along with other dogs." Donaldson functionally classifies interdog aggression into six categories based on the treatment approach best suited to correcting each.
Tarzans, as the name implies, are starved for interspecies social contact and have the kind of boorish social skills that lead them to hurl themselves at other dogs and start fighting at initial contact. Dogs with play skills deficits, by contrast, are able to greet and play but tend to get carried away and begin fighting as things overheat. Bullies are similar, except that they tend to single out specific dogs to torment, while playing appropriately with others. On the other hand, proximity sensitive dogs would prefer to avoid social contact altogether and may reactively or proactively aggress to maintain social distance. Resource guarders aggressively defend food, toys, locations, or people from other dogs. Lastly, compulsive fighters don't appear to engage in normal social behavior and have a genetic predisposition to fight. Not surprisingly, dogs may present with multiple types of interdog aggression, and classification may be confirmed or disproven as one observes the dog's response to treatment."
Book Review Mine! by Jean Donaldson
"Anal retentive to a fault (and I mean that as a compliment in this context), Donaldson does an excellent job of breaking down forms of resource guarding behavior into detailed, progressive increments. In order to teach a dog to accept having its mouth opened, for example, she lists 60 separate steps - beginning with touching the dog's rump for a single second. It takes 27 steps before one even touches the dog's head.
Clearly, this is not a book for someone who wants a quick fix to their problem. It requires a food-motivated dog and an extremely dedicated and talented owner with the patience and perseverance to apply the technique."
[ March 13, 2006, 07:02 PM: Message edited by: Mikey T ]