A bad dog

A tourist arrives at a sheepfold where he sees a shepherd with his dog near him.

“Listen, Mr. Shepherd, is your dog bad ?” the tourist asked.

“Yes, it is.”

“Does it bite ?”

“Yes, it does.”

“But I see it doesn’t bark !” said curiously the tourist.

Then the dog told the tourist:

“If so, then: Bow-Wow !”