We have a 4 year old boxer/lab mix, Maggie, and a 2 year old golden/lab mix, Mac. Both are fixed. We had an incident this morning that I'd love to get some insight on. Let me give you some background. Maggie is our alpha, and Mac generally recognizes that. When he was going through adolescence (8-12 mos.) he occasionally would challenge Maggie over resources. His attitude was "what's mine is mine and what's yours is mine, too!". She generally let him have what he wanted for a while, but we had a few scuffles as they would both go for a toy at the same time. We worked on that by never leaving toys or bones lying around the house, and reinforced Maggie as the alpha by always feeding her and petting her first. We also worked on NILIF with both dogs but especially with Mac to reinforce our status as pack leaders. He has come SO far in the last year. He now defers to Maggie all the time, like if we put a plate on the floor for them to lick, he always lets her have first go at it and won't even approach until she's done. If we're playing fetch (we always will have two balls), he will let her get her ball first before getting his. Great. We haven't had any problems for about 8 months or so. They're normally best buddies.
This morning, I fed the dogs, and Maggie finished her food first. Mac sometimes will take a few pieces of food from his bowl and walk to the carpet to eat it. Today, since Maggie was done, she kind of hovered close by while he did this. I saw her walking toward him and told her to stop, but the next thing I knew they were going at it. My husband and I got them separated and they only have a few scratches. But this has never happened before over kibble. Mac has never displayed any resource guarding with us, my husband and I can easily take anything away from him. So I'm wondering, how do we deal with this? Today, Maggie should have left him alone, but he initiated the fight. I have read about hand-feeding to help with resource guarding - do you think I need to do that with Mac? Obviously, we need to make sure they eat separately. I already make them sit before they get their food. We probably need to work on the "leave it" command with both, especially Maggie.
So Mac's issue specifically seems to be guarding what he considers "his" from Maggie. Any suggestions on how we address this? Thanks.