One of the most common aggression problems we get in here (along with fear aggression), is what I would refer to as "protective aggression". Not aggression protecting the home or family (that's territorial aggression) but aggression protecting the dog from someone invading their "space". Again, this is all too common in Border Collies, due to 2 causal factors intrinsic to Border Collies. The first factor is the "sensitive" nature of most Border Collies. They are, on the whole, a very "soft" breed, responding easily to very soft correction (except on sheep!) and over-responding to harsh negative treatment. As a breed, Border Collies do not like to be physically manipulated or handled. They're not great cuddlers, don't like having their paws or ears touched, don't like being dragged by the collar, and don't like being restrained in any fashion (though particularly by direct human contact). Now don't write to me and tell me that your dog just loves to cuddle, doesn't mind having her feet trimmed, or all the other things. All of these tendencies CAN BE OVERCOME with early socialization and conditioning by conscientious owners. And there are exceptions to any breed tendency. One of my own dogs loves to cuddle (the rest are too "busy" to want to be bothered by it). They all will, however, tolerate any form of manipulation, by me or anyone else. This took work to accomplish -- it did not come naturally to them.
The second exacerbating circumstance is that Border Collies, in general, are stinkin' smart dogs. They learn things very quickly and it doesn't take long for them to figure things out. These 2 things coupled together can lead to a very common problem. The scenario is this: a young dog (or maturing dog) is sensitive and doesn't like being handled. Owner reaches for the dog's collar and out of instinct, the dog turns its head and mouths the owner's hand or raises a lip as a threat. The owner withdraws their hand as a reflex (it's only natural to do this -- especially if it's a child). The smart dog takes this single, small victory and learns that "if I act aggressive in any way, they back off and I don't have to be handled." The next time the dog is more forceful... and the next and the next. Pretty soon, no one can touch the dog, including the owners (don't laugh, it's so common in Border Collie owners nowadays). At that point, the dog comes into rescue.
The solution? The only solution is counterconditioning and countertraining. The dog has learned a simple lesson -- the "if I act aggressive in any way, they back off and I don't have to be handled" lesson. Our goal is very simple. The dog is to learn a new lesson -- "even if I act aggressive in any way, they won't back off and I still end up being handled." Simple to say. NOT simple to do. You have to face off an aggressive dog and ensure that you don't get bit. You have to gain physical control over the dog and then continue to manipulate them (touch their ears, their tummy, their feet, etc.) until they submit and finally give in, realizing that it's inevitable. This is not for the faint-hearted or untrained (ever see the "Crocodile Hunter" guy on Animal Planet that catches deadly snakes with his bare hands? It's basically the same thing. :-) Then you must do it again the next day, and the next, and so on. Until the dog finally realizes that aggression is no longer a solution to avoid being handled. "It's inevitable so I might as well tolerate it." They don't have to love it -- just accept it.
When we go to place this dog, the dog is now back to "normal". However, given another opportunity to resume the aggression and avoid being handled, they can quickly relearn their old habit. We teach folks the signs, ensure that they understand that they must not back off at any hint of aggression (and it WILL happen at some point in time), and teach them how to respond to this situation. It's actually pretty easy to cut a dog off at this point, if you know what to expect and what to do, but the original owners had no idea the ramifications of not catching this early. A placement of this kind will also not go to a family with any children, as it is too much to expect a child to respond forcefully to any sign of aggression in a dog. Once the owners cut off the initial hint of aggression, the dog is typically problem-free from then on.
Dr. Nicholas B. Carter