Hi everyone, so my bf and i got our first long coat gsd, we had him trained with private in home lessons and he did amazing, he learned so quickly it was great. we make sure to take him to the dog park everyday to tire him out because walking him alone does not do the trick. he was great at the park and with other dogs too. However, recently he has been getting aggressive with certain dogs, different breeds, different sizes, and with intact or spayed males. i do not understand why or from where he got this way. he himself is intact but we are looking to get him spayed/neutred soon (i say both because he has one testicle in his abdomen that never desended). Anyway for the most part he's great with 99% of the dogs, but there are a few he will always start growling at even before they enter the dog park, we leave of course. oh yes and he has become possessive with toys or sticks, he will tease other dogs with it but the second another dog tries to take it he tries to snap at them, becasue of this i make it a point to not let him have anything in his mouth at the dog park. problems is people bring their balls and toys there, its rather annoying actually becasue there is a big sign that says no toys or treats :|, but who am i to tell them what to do i guess. all i can do is be firm wit my boy, but sometimes he won't listen. we are located in the south jersey area by philly and wanted to know if anyone knew any group trainers in the area, i like our private lessons but i want to change it up. I'm open to any suggestions to, he's my first dog and up to now he has been a dream, i want to keep it this way.