I'm new here and need some advice. I want to know if it is possible to re-socialize a dog that has recently become more dominant and potentially dog aggressive? I have done a bit of reading, and it seems relatively common that dogs go through behavioural changes at around her age, 18 months, but I want to ensure that this is not permanent. She used to play and interact with other dogs really well, and went to dog day care at least once a week since she was 6 months old. She has always played roughly due to her size (large), but recently she has started growling, getting her hackles up and batting smaller dogs with her paws. She hasn't bitten, but that may be because I haven't given her the chance as I remove her from the situation when this happens. She has always been insecure (was petrified of almost everything as a young pup) and been a bit of a challenge to get her to focus on me (although food is always a winner!). I have worked really hard on her training and exposure to different places, people, situations as she has grown up and now is generally great on walks through busy places etc. Also taken her to puppy school and dog obedience classes. However her behaviour seems to have gone down hill since we moved to Australia from NZ in March. We moved in with another older dog. She is great with the other dog, although they seem to have developed their own territories- she outside, him inside, where one is more dominant over the other. We often walk them together and they really enjoy each others company. We also have a friends dog that Bree gets along really well with and they have play dates once a week. George (other dog in the house) is generally fantastic with other dogs, and I would like to be able to take them together to the dog park again, but I just don't trust Bree at the moment so wonder whether taking her on a muzzle might be a temporary solution? I would like her to get the interaction, without the worry. We are going to further dog classes at a dog club and she is fine there as I distract her with food and only allow her to interact with the other dogs when she is calm. Basically I want to be able to take her out and about without any hassles like avoiding other dogs etc. I don't have the money to pay for a dog behaviouralist (uni student) and am prepared to put the time into her to get where I want to be with her. Help!