I want to clarify something. I asked if you had the puppy with you at the dog park because dogs will sometimes act differently when they have a pack member there -- dogs CAN differentiate between humans and dogs, so a pack in this sense is canine. When a dog is out and about with a canine pack member they can act differently.
This is one of the reasons having the first dog well-trained before adding a second is sound advice. Socializing and training needs to be done individually. But when you have a second dog, it should be done BOTH indivdually and together.
Once upon a time, an elderly couple had a dog named Cujo. It was a German Shepherd Dog. The old people did not train the dog, nor did they walk the dog, and their daughter who had her own dogs, sometimes took the parents' dog, Cujo to the pet store for grooming and such.
One day the old lady told her daughter that the old dog, Pip, an English Setter, was in need of a bath. So the dutiful daughter made an appointment for the old boy, and brought the young adult GSD along.
Because the daughter had been around the block a few times, she took the old dog in by himself and handed him over to the bathers. She then went outside for the huge GSD.
She walked him up and down the aisles, he saw dogs of all shapes and sizes. He saw children. He saw men, women, fat people, and thin. Dark people, light people old people. And the daughter was soon very tired. And her two hours were up, and instead of walking out to the car to put the GSD in, she went and picked up the other dog with the GSD. And wouldn't you know it some Great Pyranese dog just happened to be coming in for his turn with the bathers, as she was trying to get the old dog and the young dog out of the salon area. The young dog suddenly went Cujo on the Pyranese.
As the daughter wasn't quite that tired, she managed the situation without anyone getting bitten, but it was an eye-opener for sure. The dog was NOT like that around ANY dog before. And, after the Pyranese the dog was reacting to every dog he saw. The only difference -- well there were two differences: one was that the old dog was now with them, and the other was that the young dog and been thoroughly aroused, so his endorphins and testosterone levels (oops, he had been fixed since he was 4 months old), well his flight or fight mechanism was all the way over in the ON position.
The daughter never took Cujo and Pip together anywhere again -- walked them together through a store to be groomed, etc. And the next time she was out with Cujo, he had no problems with dogs of any sort.
While it is possible that the Evil GP stared down Cujo, and got him into an altered state, it is also possible that a dog might not act the same when there are other canine members of the family present, unless they are have excellent faith in their handler and are condtitioned to walking with other pack members.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC