Does he bite?

There was a hound dog laying in the yard. An old man in overalls was sitting on the porch. "Excuse me, Sir, but does your dog bite?", the tourist asked.
The old man replied, "Nope."
So the tourist stepped out of his car. The dog ran over snarling and growling and bit him on his arms and legs. As the dog was dragging him away the tourist was flailing around in the dust and yelled, "I thought you said your dog didn't bit!"
The old man replied, "Ain't my dog."