Aggressive Behavior - Bernese Mountain Dog

My dog did something very similar when he was young. It was like his brain just slipped and fell out. It usually involved flailing, funny noises, barking, growling, and all sorts of other weird things. Ripping holes in me when playing was not uncommon.

You may want to consult a trainer just to make sure that this is PLAY (inappropriate play, but play nonetheless) and not real aggression. It could also be frustration, which dogs sometimes exhibit as barking, growling, and snapping their teeth. Generally harmless, they're just telling you they're frustrated in the only way they know how. It's very difficult to decide that with just a description on internet, but that would be my guess considering the dog's age.

First, let's talk about the rowdy play behavior. Barking, nipping, growling, and jumping up are all play behaviors that can be mistakes for aggression, but generally if the dog is wiggly and loose, hackles aren't up (sometimes excitement causes hackles to rise, too, so not always the best indicator), and just generally looks to be enjoying themselves they're probably playing. Humans don't always like it, so it's our job to teach them to play appropriately!

I wouldn't worry about the barking and growling much. Sometimes dogs are just very vocal when they play. When the pup jumps up on you or nips at you, however THE GAME ENDS. Drop the toy and abruptly walk away. You might go inside, step over a baby gate, into an x-pen. Ignore the dog for 10 to 15 minutes. Then, after that, try to play again. Rinse and repeat. It will take lots of time, but your dog should slowly begin to understand that certain behaviors lead to the game ending. Fun is gone. If he wants to play, he has to play the way YOU want.

Second, the aggression when disciplined. My guess would be this is not aggression, but FRUSTRATION. The dog does not understand what you want. He's jumping up, barking, asking for attention, and then you yell at him! The dog is like, "Well, what the heck, I just want your attention! I'm frustrated and I don't know what you want me to do!" So he barks and growls. He's vocalizing his frustration.

Instead of disciplining the dog after the fact, set him up for success and reward him for doing the the right thing. Note, if you're doing something like ending the game when he gets rowdy or withdrawing attention, he's likely going to bark and voice his frustration. That's fine, just ignore him. But make sure to praise him and continue the game when he calms down! Jumping up and wanting attention? Turn and ignore him until he's on all four paws and stops barking, but PRAISE HIM when he does the right thing. Set him up for success by putting away things he isn't supposed to chew on, but praise him when he chews on appropriate toys! It's so much easier to have the mindset of "I'm going to focus more on rewarding the the things I WANT the dog to do than taking every opportunity to discipline the dog for doing something wrong." The dog is happier because he is very clearly being rewarded with attention and treats for a specific behavior. It's difficult for them to understand what exactly they're doing wrong, though!

If you're training a trick or something and the dog begins barking and growling and not doing what you want, he likely doesn't understand what you're asking. You need to break it down, take a step back, make it easier for him to succeed and increase difficulty more slowly.

It also helps to remember that he's a massive dog who grew very quickly and has no idea how big and strong he is and that we're rather frail in comparison! He really has no idea that he's hurting you!