This is long...
In the past month, Noah (16 months) has become increasingly possessive over his treats and space towards Sherlock (20 months) and other dogs. He has always been submissive with other dogs, very respectful around them, but also enjoys their company, enjoys doggie day care, and gets very excited when we go to the dog park. He has always wanted whatever Sherlock has and bothers him until he gets what he wants. In the past month though, he has started really bullying Sherlock. Sherlock won't even go near Noah if Noah has a treat. Noah really enjoys sitting in my lap when I am in the recliner. If Sherlock even makes eye contact with Noah when Noah is sitting on me, he starts growling and whining. This has progressed to the point where if both dogs are on my bed and I am working at my desk, if Sherlock comes too close to me or makes eye contact with Noah, Noah starts growling and stares at Sherlock until Sherlock turns away or ultimately goes and hides under the bed. I'm fed up with this behavior and every time Noah does this, I make him get off the bed. Several times he goes into time out. Yesterday I wouldn't let the dogs up on my bed (where they normally sleep). Both dogs whined and cried. I felt bad for Sherlock because he didn't do anything wrong.
The worst thing was last weekend though. The therapy organization I volunteer for with Noah had a celebration event. They had doggie games, meet and greet, and a presentation. Noah was a perfect angel during the games and meet and greet. He was very nice around the other dogs and very respectful and friendly. There was a buffet of food and food was used in the doggie games and Noah was perfect. Then when we sat down for the presentation, I pulled out a bag of dog treats they gave us. A huge lab was sitting behind us and stuck his head through the chairs and onto my lap to try to get the treats. Noah was hysterical. I think he was caught off guard, but he got very angry at the lab. Very vicious-sounding growling... he didn't advance towards the lab or try to attack, but was just growling very loudly. Once I put the treats away and blocked his view from the dog it got better. But a few minutes later he made eye contact with the lab and started whining / low growling. I got up and left with Noah because I couldn't deal with this and the woman with the lab was completely oblivious.
I'm starting to wonder if something physiologically is wrong with Noah. He did have a complete blood test and urinalysis done in September and there was nothing alarming. I'm thinking about having another test done though. He has been increasingly needy / affectionate lately. He's eating/drinking normally, activity is normal. He never shows any aggression or irritation towards humans. We go to the nursing home once a week and he is so patient with all of the residents. We volunteer in the physical therapy department so they utilize him in rehab. He's only 24lbs so the residents don't put any weight on him. He just has to sit or stand in front of their walkers or chairs while they lean over to pet him, he walks down the hallway with residents in walkers or with canes. Since his behavior towards people hasn't changed, I'm thinking maybe it's not a medical issue but maybe he's having some guarding issues that I need to work through.
It concerns me that Noah is starting to act aggressively towards Sherlock. They are really close and get upset when they are separated from each other. When I take Sherlock out and leave Noah at home, Noah greets Sherlock first and licks him all over his face and is so excited that his brother is back home.