My 20 month old beagle - Poppy - has been displaying agressive behaviour towards golden retreivers - no other dogs. She regularly plays with her best friend Lucy & other dogs, this is fine until a golden retreiver joins in, then & she goes mental. She launches herself at them barking but not baring her teeth. It looks vicious & again toinght we have had to leave the dog park in disgrace. She hasn't had a bad experience with this breed & hasn't displayed agression towards any other type of dogs. I have had her since 8 weeks old & thought I had socialised her properly - really do not know what to do.