DEAR JOAN: We have two family dogs -- an 11-year-old yellow Lab and a 5- or 6-year-old flat-coated retriever. They're great friends, take daily walks together, sleep together, play and wrestle together. They are the sweetest pets you could ask for.

However, over the past nine months or so, the flat coat has become aggressive toward the Lab after meals. He takes a little swipe at him, won't let him in the house, and then when they are in the house, he gets all whiny and barks until someone pays attention to him. We've worked on this issue and seem to have a handle on it.

Learning to get along.
Learning to get along. (Michael Chritton/Akron Beacon Journal)

Lately though, the flat coat has attacked the Lab out of the blue. He dives on him, starts biting his face to the point where it draws blood and has to be separated by my wife or I, which takes serious effort. The attacks frequently happen while we're all sleeping, the Lab on our bed, the flat coat in his bed in the middle of our bedroom. He wakes up, then launches onto our bed and dives on the Lab.

We'll swat his nose, then throw him out of the bedroom and close the door. It may not happen again for a week or two, but when it does, it's the same story. We're thinking perhaps a soft muzzle for sleeping is the answer but would appreciate your advice.

My wife feels this behavior may be directed toward her as the flat coat continually wedges himself between the Lab and my wife or repositions himself for the "better spot" on the couch or bed when Lab is there.

Doug and Dom Gotelli

Bay Area

DEAR DOUG AND DOM: Aggressive behavior in dogs is never random or without reason. The key is finding the trigger, and it's not always easy. In this case, however, I think you've already found it.

It sounds as if the flat coat is jealous of the attention the Lab gets. Why it suddenly occurs to him in the middle of the night, I have no idea. When you have dogs fighting over anything -- food, a toy, their human -- it's best to remove the object of the dispute.

I consulted expert dog trainers, and they say first of all, you need to get the Lab off the bed. Allowing a large dog to sleep in your bed is not a good idea. The dog may decide it is his bed, elevating his "pack" position.

I'd get the Lab his own bed, and I'd put both of them in another room. If you're worried about them fighting in the night, then put them in separate rooms, but not your bedroom.

Whatever you did to work on the earlier behavior, keep that up, but if the dogs should get in a fight again, throw a blanket over them to disrupt it. Remain calm and show that you are in control. Dogs take their cue from you, and if you are excited and agitated -- I know I would be if I awoke to fighting dogs in my bed -- then the dog will think he should be excited and agitated, too.

Don't put the flat coat out of the room. That could leave the altercation unresolved, resulting in the fight starting again when they are together. Calm everyone down and then separate them if you're worried.

The last piece of advice is to take the flat coat to the vet for a checkup. Judie Howard, a well-respected Bay Area dog trainer, says the behavior you describe is very unlike a purebred flat coat. They remain puppylike for most of their lives and are not known for aggressive actions. Make sure there isn't a physical problem that is somehow triggering it.

Contact Joan Morris at jmorris@bayareanewsgroup.com. Follow her at Twitter.com/AskJoanMorris.