Looks like you may have used a training acronym. For those unfamiliar, here's some of the common ones:
BAT is Behavior Adjustment Training - a method from Grisha Stewart that involves allowing the dog to investigate the trigger on their own terms. There's a book on it.
CC is Counter Conditioning - creating a positive association with something by rewarding when your dog sees something. Think Pavlov.
DS is Desensitization - similar to counter conditioning in that you expose your dog to the trigger (while your dog is under threshold) so they can get used to it.
LAD is Look and Dismiss - Marking and rewarding when your dog sees a trigger and dismisses it.
LAT is Look at That - Marking and rewarding when your dog sees a trigger and does not react.
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> We've tried to curb the attitude with praising good behavior and giving stern "uh-uh"s to bad episodes.
The first thing to note is that verbally scolding your dog is going to have very little affect here. This is not a productive way to address reactivity or aggression. These behaviours stem from stress and fear. Scolding your dog for being stressed and fearful is not going to reduce that stress or fear.
You don't mention what kind of terrier your dog is, but as u/adaneko mentioned, there are breeds of dogs that are known to be prone to dog selectivity as they mature, and certain terrier breeds are among them. Every dog is typically more dog-social or dog-tolerant as a puppy, and it is normal for that to change as they mature. So, a dog-social puppy may become a dog-tolerant adult, or a dog-tolerant puppy may become a dog-selective adult, and so on. This is within the range of normal. Part of your role as owner is managing your dog and setting them up for success, rather than simply scolding what may be a fixture in their adult temperament.
Obviously, it is not ideal to have your dog lunging and snapping at other dogs. Think about what your dog is communicating here. He's uncomfortable. He's stressed. He doesn't like having a dog in his space. With that in mind, you should not be taking your dog to dog parks any more - for the most part, dog parks are really only appropriate for very resilient dog-social dogs. Your dog is clearly communicating that, in certain cases, he is stressed and uncomfortable being around other dogs. You need to respect that. It is too risky for your dog to be interacting with strange dogs that he may snap at. You do not know the history or triggers of other dogs at the dog park. Your dog could end up seriously injuring another dog, or being seriously injured by one that does not respond well to being snapped at.
You also need to stop greeting other dogs on leashed walks. This is recommended even for dog-tolerant dogs. Leashed greetings are stressful because they reduce your dog's ability to use polite body language when greeting another dog. Leash reactivity is incredibly common. If you're on a leashed walk and you see another dog approaching, cross the street or indicate to the other owner that your dog is not friendly and avoid each other as much as possible. This is your responsibility as an owner of a leash-reactive dog.
> I want to curb the behavior but any chance I get he becomes so aggressive that he bites and latches on.
I'm unclear on what you're describing here - are you saying you put your dog in situations where he has to interact with other dogs, because you want to work on the behaviour, and he has ended up biting other dogs? This is extremely inappropriate. You should not be doing this. If your dog has escalated to repeatedly biting other dogs, he needs to be wearing a muzzle when he's outside your house and you should be avoiding other dogs as much as possible. Biting is a stressed dog's last-ditch effort to get out of a situation they are extremely uncomfortable in. You need to stop putting your dog in these situations.
Head over to r/reactivedogs. Check out their wiki and read through everything there. I would especially recommend picking up a copy of Behavior Adjustment Training by Grisha Stewart.
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There's a book on it.
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