You have to be strict with him from the get-go. I got my boxer as an adult but i've helped raise brothers dogs who both went through nipping stages.
What we did when they bit, was yell "NOOOO" and tap them on the bottom of the mouth.
Our secret was the "no" part. Don't be afraid to yell it
I think the trick is being consistent and letting them know that biting is not acceptable behavior.
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tie - 12-year-old flashy brindle male
Newman - 2 Year Old flashy Brindle male
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