Question: why are pugs tails curly?
Answer: DEAR MASON: The curly tail is the result of a spinal deviation. Vertebrae (the bones that make up the spine) are wedge-shaped, and since dogs' tails are both bone and cartilage, pug tails will have a natural curl. Breeders have turned a deficit into an asset, and the “breed standard” for pug dogs is for a curled tail.