Dog increasingly aggressive over food

Question
Hi recently my family has been having problems with our 3 year old king cavalier spaniel poodle cross. He has always been slightly aggressive when given bones as treats but recently it has become a problem with his daily bowl of food. Recently my brother has moved in with his wife and child while waiting for their new home to come available and brought with them their cat. My dog (Scruffy) gets long very well with the cat normally and they even play and sleep together. However ever since the cat has moved in he will not let anyone go near him when eating. His food is in the kitchen and so if anyone merely walks buy he will start growling very aggressively. Bit my brother recently when being fed and I was forced to lock him in the bathroom this morning because of his behavior. He is neutered and we have tried various tactics to stop the behaviors such as feeding him outside or sitting with him as he ate and petting him. Locking him up generally causes his behavior to improve after the fact but I know it is not a solution. Please help!

Answer
The behavior you are describing is called "resource guarding" As you noted, the behavior was already there, but has gotten worse. I suspect that the addition of family members - including a child, more than just the cat (unless the cat is teashing him while he eats - not unheard of) has made him  more vigilent. I would be hand-feeding (dropping a kibble or two into his dish at a time) and doing it in areas other than the normal location for eating. If he's really guardy, you may want to step in, toss a treat in the dish and step back in the beginning. Don't put him in situations where he feels he needs to bite. And if you make a mistake and get growled or snapped at, don't try to "win" the confrontation. You must be VERY careful with the child, as RG is a reason a lot of children get bit - they don't notice the warning signs, and are likely to try to take toys, etc. Work slowly on the problem - handfeeding, doing trades, doing lots of passive leadership exercises - ask him for obedience behaviors (if he knows any) for anything he wants - food, petting, play, etc. You could really use an inperson good positive trainer to help you through this, and a good book on the subject is "Mine" by Jean Donaldson. Good luck. Sandy Case MEd, CPDT www.positivelycanine.com