[alaskayorkie]

I'm no expert, but it sounds like a dominance issue. Almost like Starsky is challenging Haggis as pack leader. Would you say Haggis is the alpha of the pack? He's getting older, and that's just one of the things that happens.

Deciding what to do about it is the tough part. The first thing I'd suggest is to make sure you've established yourself as pack leader. You do that by controlling their feeding schedules and toys, being first to walk through the door at walk time, etc. After that, some people advise letting the dogs work out the hierarchy between themselves. But only if there's no danger of them being seriously injured. If there are actual bites that do or could bring blood, then you have to step in and break it up.

But make sure you don't scold the aggressor. Just break it up and remove anything they are fighting over. Scolding the aggressor could just lead to resentment that the aggressor will hold against the other one later when you're not around.

Another thing, maybe the first thing, is to make sure they are all getting plenty of exercise. A tired dog is a happy dog.

But, again, I'm no expert. Behavioral issues are science, and I may be missing the point entirely. Good luck.