Formal training may help: My 7 month old ECS is extremely possessive of her person, her toys, her snacks, her food, her bully stick, etc. I guess it can be a problem with spaniels. Fiona has zero problem with her people taking food, socks, the kitchen scrubby, wash cloth or anything else that catches her fancy. She will give them up without aggressiveness-- albeit reluctantly and she is a little thief of the first water. However, let another dog nose around a pile of my dirty laundry or another puppy in obedience class comes around for a pet, she will growl, (I ignore it or tell her No!). She did this for the first time when she was only 3 months old. If my older beagle tries to sit next to me she will try to growl and I respond with a matter of fact "No!" and Fiona has to get off of the couch. People think that she is this soft sweet spaniel but she really has kind of a pushy, rather dominant personality with other dogs. I believe that the problem would have been much worse if I didn't spend time training her. She is very active, engaged and energetic(when asked to pick one word to describe my puppy when she was 9 weeks old, the breeder used the word "busy,") --so I funnel all of that into obedience training. Teaching her to release on command is one of my current goals. It will allow me to replace food with a toy for obedience training. It is a challenge, to say the least. The game of tug has specific rules, if they don't release the tug then you simply hold it still and the game doesn't continue until they release it and sit. Then you release the dog into another round of tugger. The idea is that the dog will figure out that they have to release the toy in order to play the game again. You probably need someone who knows just how to do this to show you and explain it better than I can. I bet it could help you.