*sigh* Well, here goes...
Lately, Riley has been acting aggressively with other dogs he sees on walks. He wasn't always like this, it's just picked up in the past couple of months or so. Honestly, I should have given more attention to it, that's my own fault. The thing is, we go to the dog park at least once a week and he's fine with the dogs there (except he'll growl if another dog tries to take his ball). Then, at the Irish Festival a few weeks ago, he totally FREAKED out on this other Irish Setter. The dog walked over and was just sniffing Riley, and Riley growled and began baring teeth. I don't know what's brought these changes on, but I'm thinking his age has something to do with it (he's 2 1/2).
Lately I've really been cracking down on this and taking him on more walks versus off-leash play sessions (he's fine off leash, seems to be more aggressive when on leash). When a person with a dog comes in our view, I ask him to sit and give him lots of treats and try to keep his attention on me. This usually keeps him from freaking out, but he's still constantly looking past me and staring at the other dog. I bought a spray bottle and set it on mist and just today began giving him one spray when his body goes rigid at the sight of another dog. Is this the right idea?
The thing is, I'm confident that were he to meet any of these dogs at the dog park, he wouldn't freak out so much. He hates it when other dogs invade his personal space, such as jumping on him, but he doesn't bark/whine at them then. Does this classify as leash aggression?
I've also considered the possibility that he's developed a thyroid condition. Irish Setters are prone to it, and his stomach has a large section that has very sparse fur and dry skin (it's always been that way), and his coat has little feathering on his stomach and abdomen (though that could just be his coat genetics). One of the symptoms of hypothyroidism, however, is weight gain and obesity, and Riley is a thin and very fit dog. He had the T4 test run once before at the vet, but the results showed that his levels were only very slightly low.
I guess I just need some advice. Do you think this could be related to a thyroid condition? Or is it exclusively a behavioral issue? Also, am I taking the right steps to curb this behavior?
Sorry this ended up to be so long....thanks for any help!