using a prong correction for aggression can sometimes have the opposite effect you want it to.

prong corrections can amp the dog up more.

You said you had to use 3 hard corrections with the prong, what did the dog do after the first hard correction you gave him?

 Quote: Wendy Lefebvre

using a prong correction for aggression can sometimes have the opposite effect you want it to.

prong corrections can amp the dog up more.

Yep, drive,compulsion, more drive, compulsion, even more drive.

I am certainly no expert, but it would seem strange that the dog has suddenly become dangerous. Maybe there are other cues to his behavior? And maybe he is having a fear stage or is insecure about something. My dog is about the same age, but still needs TONS of work. I feel that I can never let up.

I would make sure to do some walks where he has to focus on you and not so much on what is going on around him, if you are not already. I use "leave it" a lot when I walk by someone. And BTW, I am still walking by other dog walkers at a distance (across the street) or else we sit aside in the grass to let others pass us - focusing on me and ignoring the others, this includes walkers without doggie companions as well.

I encourage Maggie to ignore other people as well as dogs. She is not to be interested in them or afraid of them either.

NOT an expert, NOT a trainer, but have seen dogs turn on their owners, so someplace in yourself(hidden from him) keep your guard up.

Time for a Vet visit.
Sudden, explosive aggression in a dog that has shown no hint of it before could indicate a lot of different health issues.

When you say he was previously territorial, what do you mean by that?

Beyond that, is it possible that he had a frightening experience with someone when you weren't around? Someone taunting him in the yard, for example?

 Quote: aaron myracle

Time for a Vet visit.
Sudden, explosive aggression in a dog that has shown no hint of it before could indicate a lot of different health issues.

When you say he was previously territorial, what do you mean by that?

Beyond that, is it possible that he had a frightening experience with someone when you weren't around? Someone taunting him in the yard, for example?

also: using a prong correction for aggression can sometimes have the opposite effect you want it to.

prong corrections can amp the dog up more.

You said you had to use 3 hard corrections with the prong, what did the dog do after the first hard correction you gave him?


Yes, I'd like to hear all these answers, too.

And I'd like to re-recommend the vet visit as well as a good trainer visit. JMO.

I would want a visit from my trainer in person and asap, and the vet visit scheduled soon. But TRAINER. "I don't trust the dog" is close to "I'm afraid of the dog;" being afraid of your dog is a deal-breaker. Again JMO.

Okay, to reply to some of your comments:
> Prong Corrections: I administered a couple of corrections in a period of about one second after yanking him back (which would be the first correction); he immediately went from attack to "normal" mode, and sat down on command. So the corrections stopped the aggression, actually after the first one, now that I think about it, and he had no issue with obeying the next command.

> Diet: What would the Vet be testing or looking for? Would it be a blood-work or something?

> Territorial: He has always barked very forcefully at any creature that steps into our yard, be it cat, squirrel, human. And if he has a line of sight and some room to run, he goes like a shot, though he has self-corrected enough to learn where the end of his line is.

>Frightened: That is a possibility, since you can never know what happens when no one is there. The backyard is entirely enclosed six feet high, and his wire kennel is connected to the back of the house, but not the fence. So there are two seperate enclosures, one inside the other. Not to say it can't happen, but someone wold have to TRY to taunt him.

> Walking: with "space" around is obviously what I am going to have to do now. But we were working on the Canine Good Citizen exam, which among other things requires the dog to tolerate strangers next to him, even touching him. Just three months ago, we participated in a charity walk with three thousand people, without any problem.

>Trainer: I have an appointment to take him for a consultation at the K9 Orlando Center; which is one of the primary K9 training facilities in Florida. My primary trainer agrees that is a good approach.

 Quote: Robert McFarlane

And if he has a line of sight and some room to run, he goes like a shot, though he has self-corrected enough to learn where the end of his line is.

Wait wait wait.

Self-corrected to know where the end of the line is?
Are you chaining this dog?

No; only when he is sitting out in the front yard, then he has a twenty foot plastic coated steel cable attached to the flat collar; But he is only out there when someone is also in the yard, doing work, washing the car, whatever. Because there is no fence around the front yard. So the first couple times when the neighbor's cat came around, he hit the end of the line. Now he knows when to put on the brakes.

Okay.
I ask, because for some dogs, tethering can cause or exacerbate aggression issues.

While I don't think the duration and sort of tethering you're describing would *cause* this issue, I do think it would be wise to discontinue tethering him like that now that there are issues.

I didn't answer your other questions because I wanted to clear this one up first.

The Vet should be considering one, whether his hip dysplasia is progressing, and whether it has progressed to a degree that the dog is in pain. You mention that he recently was with you at a marathon- it's not entirely outside the realm of possibility that if his hips began bothering him during the marathon, he associated that pain with the crowds, and is attempting to protect himself from people as a perceived source of pain.

A general Vet examination is definitely in order when a dog displays a massive change in temperament. Dogs are very unlike humans when it comes to pain, and sometimes the only indicator of discomfort or feeling unwell is a change in behavior. They will often not limp and seem quite stoic about their pain, but instead develop odd phobias because they attribute the pain to something external. Dysplastic dogs have been known to become phobic of certain surfaces, for example.

I'd also want the Vet to pay particular attention to his eyes and ears. If he's having a change in the way he perceives his surroundings, that could cause him to become fearful and thus, aggressive.