The Manx cat (formerly often spelled Manks) Manx language: kayt Manninagh is a breed of cat with a naturally occurring mutation of the spine which shortens the tail resulting in a range of tail lengths from normal to tailless. Many Manx have a small stub of a tail but Manx cats are best known as being entirely tailless; this is the distinguishing characteristic of the breed and a well-known cat body-type mutation.