When we think of scary cats, we are likely to imagine the typical “Halloween cat.” We usually see him from the side with an arched back and his fur standing on end. The ears are flattened against the back of the head, the corners of the mouth are pulled back to bare the teeth, the whiskers are drawn against the side of the head, and the nose is wrinkled. These cats can look pretty scary.
And that’s the point. Cats that display this posture are usually in a frightened and defensive mode and are merely trying to look bigger and more threatening to the opponent. Turning sideways with the back arched presents the largest view of the cat’s body. Arching the back is usually accompanied by the hair standing on ends, called piloerection (pil is Latin for hair), especially on the back and tail. This is the same thing as the goose bumps that you experience when you’re frightened or cold. Piloerection is caused by constriction of tiny muscles at the base of the hairs and helps to make an animal appear larger.
Cats are able to arch their backs because their spines contain nearly 60 vertebrae, twice as many as humans have. Cats are very flexible; their lifestyle includes plenty of stretching and relaxing to encourage this. The cat’s daily routine includes a precise and complex stretching exercise. Watch your kitty when he first wakes up. He will likely stretch his paws in front of him, elongating his body with his rump and tail in the air. Then he will pull his back up into a high arch. He isn’t feeling threatened, of course; but he is keeping himself in shape so that he can assume the posture when he needs it.
Cats aren’t the only members of the animal kingdom that use this ploy. Several animals assume a defensive threat posture when they feel threatened. For example, the cobra snake raises the front part of the body and spreads his neck into a hood; mammals, including the dog, raise their hair or fur; lizards inhale air and hold their breath; and fish erect their fins and intensify their colors.
All of these behaviors make the animal appear larger and more threatening and are all meant to cause a potential competitor or predator to look elsewhere for a smaller and less daunting victim.