resource guarding Bichon

Question
We have two neutered male Bichons, aged 11 and nine years.  They get along and have both passed Canine Good Citizen classes and tests.  The 11 year old has been getting "attitude" problems; for example, pulling to go another way while on walks, waiting to be called twice for dinner, and being slow to respond to commands in general.  Recently, I gave them raw marrow bones in an attempt to help with tarter problems.  The 11 year old began to seriously guard his, and last week lunged at the 9 year old when he got too close.  Last night, when my husband tried to put the bone away before bedtime, the 11 year old seriously bit his hand.  We started a "nothing in life is free" regime right away, not allowing him on the bed even when he whined, making him sit for his leash and food, and heeling while walking.  Is there more we should do or can we no longer trust him around people and dogs?

Answer
First, remove the bones.  Tartar buildup correction isn't important given the dog's failing behavior.  Brush his teeth instead (both dogs).

Your dog is in his senior years and what you're seeing is most likely the result of some cognitive failure.  Dogs at that age, especially with the sort of excellent education you've provided them, rarely develop aggression problems; for a dog to escalate from zero aggression to actual biting, with no interim warning (aggression normally starts with a growl and slowly escalates to breaking skin) tells me he has some loss of cognition.  His bite inhibition is gone (zero bite inhibition), this doesn't occur overnight.  It is also possible he's not feeling good.  Take this sudden change in behavior to the veterinarian.  Ask for basic neurological evaluation (which may not indicate a problem, that doesn't mean there isn't one) and full blood chemistry along with overall health check (palpation of abdomen, ear check, eye check).  I have a strong suspicion the dog is either in pain physically (making him hypersensitive in all departments and less likely to 'listen') or suffering from the onset of age related loss of cognition.  If he is ill, then your remedy will be determined by the veterinarian.  If he checks out perfectly healthy (full body x-ray might also be considered although this means the dog has to be sedated, normally), Selegiline is a medication being used in age related cognitive dysfunction.  It certainly can't hurt.  Keep the dogs (BOTH of them, you can't just demote one) on your NILIF regimen: this is an excellent idea.  Keep them out of the bedroom and off the furniture.  This will help both dogs feel more secure (sounds contradictory but it does) while maintaining their relationship at status quo (not promoting the younger dog by allowing him privileges denied to the older dog.)  Meanwhile, do nothing about this dog's apparent ignoring commands.  In the weeks following his vet visit, you can go back to square one with this dog and re-teach him to respond at the first command.