Sounds like maybe your puppy is starting to mature. He might be asking other dogs for a little respect now. You'll need to step up your leadership and let him know that that type of behavior isn't part of the game.
Hondo Von Dopplet L Bauernhof "Hondo"- GSD
Lilie's Tug McGraw "Tug" - Golden Retriever
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Lonestar Pivo - Texas Blue Lacy
Ashe - Barn Cat
Katie / APHA