[QuickSilver]

Bummer! Thor has major aggression problems with other dogs, but at least it's fear aggression. Bottom line, he is happy when the other dog goes away.

I'm sure this has occurred to you, but has he had a bad experience recently with a larger dog? Also, what do you think he is trying to achieve? Is he protecting you? Is there something else in the park he is guarding? Is he "hunting" the other dog? Is he trying to scare it away?

Thor looks very "dominant" when he gets aggressive, but it's very clear that it's all bluster. He lunges forward, snaps, barks like crazy, but he just wants them to go away. I also feel that it's potentially dangerous. We've been working on it for years and years... sigh.

Also, dogs can easily tell if another dog is a puppy, so that doesn't surprise me that he would deem a large breed puppy unacceptable.