Young dogs and first grouse, what a great combo for sure. My first dog could pick up a uncooked egg and carry it around without cracking it.
My second dog can put bite marks in rolled steel.
Never seen a setter with a hard mouth. I'm guessing that one was in a position where the pup couldn't get a good grip on the body and thus the tail was the only area she could reach. PS. Nice wood on that repro.