Hello Lisa, thank you for using this site to help you with your problem. My name is XXXXX XXXXX I have been in the dog field for 25 years. It will be my pleasure to help you today. Please understand that I may send an information request so that I may gather what I need to better help you with your problem.
Generally when dogs are truly protective of their owner they are silent about it and act when they feel there is a situation that warrants it. They are not likely to act out in the manner you describe when they are protective unless they were trained to be vocal about it.
Most humans mix up protection with possession. With possession the dog thinks they own you thereby warding off every other dog or human that comes near.
There is also fear aggression in which a dog will act out because they feel there is no way to get out of a situation.
Grabbing the neck /collar area and forcing a dog down is not a way to train him to stop, It is an outdated method that has been proved time and time again not to work. Humans feel that because this is how a mother dog reprimanded their pups that this is okay to do to them, when in fact it can really backfire and make situations worse. In the dog’s mind when this happens he is associating an unpleasant act with meeting another dog or person and the longer it goes on the dog may act out more and more. Then they start to act out in anticipation that coming upon another dog/human is unpleasant so they begin to try and move everyone away from them by barking and lunging to avoid that unpleasant act (the scruff grab) before it happens.
Rescue Remedy is also outdated and rarely works as you are finding out, especially for aggression in dogs. I am not aware of any real clinical studies for this product on dogs.
( the company that makes the product may have boasted about this for pets) . Either way it is not working for your dog and that is what is important
What you will want to do with this guy is daily obedience training so you can stop a problem before it starts. Get the commands Heel, leave it , sit stay, and quiet down 100% before taking him out in public again. By taking him out in public or around other dogs at this time you are setting him up to fail because you are putting him in a situation that he only knows one way to act, so over time it has become a learned behavior, a pattern if you will, and you want this pattern to stop.
As it pertains to your other dogs at home, keep them out of the situation that sets them off and for a while this may mean gating off an area for this dog until you have had the time to work with him.
Training should be done in shorter sessions but several times a day rather than one long daily training and here is why. When you train throughout the day the dog sees you as being a consistent leader. When you only train for one long period a day, the dog learns that this is just part of his daily routine and that for this time only you want him to behave whereas when you do it throughout the day the times will likely be scattered and you will be doing this inside the home and out in your yard, these scattered times begin to tell the dog that you expect him to behave all the time.
Gradually you will take the dog onto the street briefly and make sure when you see another dog coming, you give the commands. Keep him in a sit -stay and give the leave it command. You will want to do this briefly to start, possibly only a few seconds is all he will be able to handle, then release him from the command sit-stay put him in a heel and take him away from the situation before he has a chance to act out. By doing this you are setting him up to succeed. Eventually you will build up the time he is in a sit-stay until there is success when another dog passes him. Once that is done you can proceed to working on heel and leave it on the street for a walk.
There is no overnight cure for this as this behavior has been going on for a long time so he now has to unlearn it and learn a new way to act.
I am going to direct you to a site for clicker training which is a positive based method so you can get started on the commands above.
The reward value as you move to the outside world should be high to keep his attention so if you use Turkey hot dog slivers in the home and around the yard for training, when you get to the street you want to up the value to chicken slivers. ( just don’t use any human food considered to be fatty or this can cause pancreatitis) . Make sure the dog is hungry at the times you train , if he has been fed his kibble he won’t be so interested in working for you.
I would also use the NILIF training as this will help with possessiveness as well work in conjunction with the short trainings you will do throughout the day. I will direct you to a link on this as well which goes over how and why it works.
You may also want to look into any health reasons causing the aggression such as a thyroid problem. Your vet can do blood tests to see if there is a problem in that department. If the thyroid levels are off even a little it can produce aggression.
When you are at home put a harness and a short (2 foot) lead on him so if he looks like he is going to squabble with your other dogs you can stop it via the lead. At the same time you want to give your command Leave it.
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Clicker training/positive method training
video’s to see how clicker training is done, scroll down to videos http://www.clickertrainusa.com/clicker-training-videos.htm
Nothing in life is free
Training method BAT (this explains how to do it in short sessions for success