So we adopted our boy from the shelter around 6 months ago. The shelter had said he was turned in for biting but on further investigation they couldn't get him to bite and the people who had turned him in had a long history of domestic violence and assaulting the officers who responded. He has been wonderful for almost all of the six months but the past few weeks we are noticing some more aggressive behavior. We make him sit or lie down or any other sort of combo of tricks before he gets anything from us (includes food, walks, etc) and the first time I noticed some aggression was when I was making him sit to go outside in the backyard. He jumped up on my arm, crossed his paws over it and took my hand in his mouth. He didn't bite down but it wasn't friendly. I told him "too bad" and put him in time out.
Last week we were out walking and he found a nasty piece of paper towel on the ground with something on it. He started eating it so I stuck my hand in his mouth to retrieve it. He brought his teeth down on my fingers, started growling and bared his teeth at me. I yelled at him but it didn't stop until I let go of the paper. He didn't bite me enough to break the skin but was putting pressure with his teeth on my hand. I didn't know how to discipline him properly as we were 2 miles from our car so we tried to ignore him for the walk back to the car.
While he was baring his teeth at me I saw one of his top teeth was all broken so we had it extracted yesterday by the vet. When I went to pick him up, the vet came to meet me and told me about how they had to use a rabies stick on him to remove the catheter in his arm. He was apparently great all day until then and even with a muzzle he was being very vicious and aggressive and trying to bite them. I don't really know what to make of all this and the vet talking to me about how he could be dangerous scared me a bit. This is my first dog so any and all help/advice would be much appreciated. Thanks a lot!
Abram