After the fight I mentioned that maybe we could test out gating Lincoln in the kitchen by himself while we're both out and having the other 2 separated too (a 3 way split) and see what happens. I'm wondering if Lincoln can't see him/us come home (but can hear the truck, it's pretty loud) he might be inclined to simply lay down and wait because he can't see him out the window. And if he's not around the others, it won't cause tension with excitement. He got offended when I mentioned it, so I dropped it.
I think separating when you're not home to manage is your best option. I wouldn't trust Lincoln out with the other dogs when you're not there - it sounds like it was a bad fight and the more times the behavior is practiced the more it's going to happen. When you are home you can work on doing things with Lincoln when your OH gets home(I know he's not your dog but your OH seems completely disinclined to work on this so it's probably going to fall on you
).
We have a similar issue (excitement triggering a fight) in our house. What we've done is set up a system where we call each other before we get home. EVERY. SINGLE. TIME. That way we can either separate the girls, or set up the situation to be managed.
My management system goes like this:
- Matt calls to let me know he's on the way home.
- I make sure that I have treats somewhere near me (I usually keep a stockpile in the end table). I try to make sure that none of the dogs know I have them, I don't want it to be a bribe, I want to reward them for the right behavior.
- When Matt's car pulls into our cul de sac everyone goes on alert. In the beginning this point is where I started stuffing treats into Mu (who is the attacker in this situation). We're at the point now where I can wait until Matt actually gets in the door to reward her. If she's acting really antsy I will click/treat for looking at me before he gets to the door.
Using this method we've gone from a near certain fight to almost no fights ever (for this particular situation). For us it had the added benefit of desensitizing Mu to trucks pulling in and out of the cul de sac, which was another trigger.
My dream goal that will probably never happen? When Matt gets home and/or someone knocks on our door all the dogs go straight to their mats and stay there. I currently don't have ONE dog that will do this (although Mu will stay in one place as long as its near me) so this is really a pie in the sky goal.
I hope this helps! It's a sucky situation but if this is the only area you've had fights in and you've only had the one it should be pretty easy to manage.
ETA: I forgot to mention - in the beginning of us working on this I was actually contributing to the fights. The dogs would alert to something in the street and I would get SUPER anxious. Which they picked up on, which made them more stressed out, which caused a fight. The biggest thing I did to help this was to SHUT UP and take deep breaths. When we go through our routine I generally don't say anything at all. I focus on rewarding at the right time and taking deep breaths. I don't know if this is an issue you'll encounter but I thought I'd mention it because it took me forever to figure out what was happening.