Today we had guests who brought over their 3 month old lab. Our 3 month old labradoodle Dunkin was very defensive. They sniffed eachother and then everything turned. Our dog was not happy. He growled and nipped and barked at the other puppy the entire time. We had to put him on a leash and hold him with us so he wouldn't go after the lab. He could not relax and acted more aggressive then we have ever seen him act. We have 2 other dogs in our family that he is always with when we go visit. Dunkin has also been to the dog park about 2 days a week since right after Christmas where he meets all kinds of dogs. I don;t know why he acted this way. Was he just being possessive of the home, since this was the 1st time another dog has been here? I am concerned. Any ideas? He starts with the trainer next week. :?