I have a five year old male chihuahua, Dash. I also have a two year old female, Sissy. Neither of them have been spayed/neutered. Dash is actually going for his surgery tomorrow. We've had Dash since he was about 9 months old, and Sissy came to live with us when she was about 8 months. Dash has been giving us some behavioral problems, and it is starting to worry me. He had been growling at all of us when anyone would pick him up. This led me to believe he was hurt, however, he is not showing any symptoms to anything. And Dash only snapped every once in a while. Then last Thursday, my daughter accidentally left our door open when both Sissy and Dash darted out the front door. Dash nipped at a neighbors pants when the neighbor started stomping at him and Sissy, then the neighbor tried to squish Dash under his feet (Dash is only 4 lbs.). Since then Dash has been extra mean, he has bitten me and my fiance. I have no idea what has gotten into him. He used to be very loving, but now I am starting to fear him. We are going to the vet tomorrow to get him neutered, and I am hoping his aggression levels come down. Has anyone else experienced this with their dogs? And did the aggression go away? I miss the way my boy used to behave. I do not want to have to put him down because of his aggression. He has too many years left to live!