Barrier (behind fence, window, on leash) This category is often called Barrier Frustration because even though it can look very intense, it does not mean that the dog will, if given the opportunity, engage in an aggressive manner. This type of “aggression” simply put, happens when a dog cannot get to what they want and that frustration builds which causes the dog to get even more ramped up and the behavior intensifies. It is often seen paired with Redirected Aggression. Some dogs may display this when wanting to greet other dogs or people on leash and when restrained, throw a tantrum by barking, pulling to the point of choking, looking like a hooked fish on a line, and/or nipping or fully biting the handler or leash (there are also usually underlying issues of entitlement and Leadership/Pack Structure issues).
In certain high drive breeds, this ramped up mental state, even though wasn’t started because of aggression, it can often turn into aggression quickly because of genetics (predisposition to aggression).
Health (chronic conditions such as an ongoing ear infection or poor hygiene) Health should always be a consideration when looking at behavioral issues such as aggression. Something as simple as an ear infection can look like social aggression or depending on severity, could look like fear aggression because when someone goes to pet the dog they are aggressive. It could simply be that the dog has enough chronic pain that it’s easier to just keep people away from their head. This behavior can also apply to feet (nails being too long), or even something more subtle such as hip dysplasia.
Medical (conditions such as hypothyroidism, neurological, or genetic) From a percentage point of view, most aggression issues do not stem from medical issues, but they do exist. Hypothyroidism is one such medical condition that can cause aggressive behaviors. When diagnosed properly, it can be treated fairly successfully, but usually there is still other issues that have to be addressed through a training and management plan. The biggest issue when dealing with hypothyroidism is getting a proper diagnosis. The tests that the average veterinarian runs for this, is not sufficient to pick up on the markers unless there are other clinical signs when the issue becomes more advanced after years of cumulative damage. If one feels this may be a possible reason their dog is aggressive, I encourage you to look into HEMOPET and Dr. Jean Dobbs and have your blood work sent there. They are one of the only facilities capable of running an in-depth test.
From my experience when dealing with this as a potential cause, we are looking into it because, we have done training and/or an assessment and variables such as Leadership/Pack Structure, entitlement, breed variables (Dobermans are predisposed to this), cohabitation, etc. have all been addressed and we are still having aggressive episodes. The reason I say episodes, because a lot of times that is what it is, episodes of aggression and not a constant state of mind or personality. They are often seen/described as their ramp up is being very manic and is triggered by normal interactions that may not have been an issue when done for years. The “snapping” out of it is usually just as quick and manic as if nothing happened. There is of course varying degrees to the behaviors depending on how long the medical condition has been affecting the dog.
Resource/Object (beds, couches, people, toys, and even affection) Resource guarding a lot of times is the final straw for people to seek help. Resource guarding can take on many different triggers, but they all stem from the same state of mind, ENTITLEMENT and an unclear understanding of what the rules, boundaries as structure are for that particular situation. Reshaping the relationship to reflect one of mutual respect and that the owner/handler is a fair leader who will PROVIDE life’s essentials instead of the dog being ENTITLED to them, is where a lot of understanding is needed in order to address this type, or other aggression. In order to address this issue properly, one needs to understand dog culture and how that shapes a dog’s understanding of their interactions with us unless we put in the time to teach them otherwise.
Resource guarding areas of rest such as human furniture (chairs, couches) and beds, is one of the leading causes of children getting a bite by the family dog. The damage done goes up depending on the breed. Too often people look into this area of aggression after the fact instead of putting in steps to minimize it from ever happening from day one.
Resource guarding of food is a separate issue discussed in Food Aggression.