Old World porcupines, such as the Indian porcupine (Hystrix indica), have longer spines than their New World counterparts. This species has a short tail which, as well as being covered with sharp quills, has a cluster of hollow quills. These quills are shaken in warning and produce a sound similar to that of a rattlesnake. Porcupines attack in self-defence and usually run backward toward their attacker, releasing the quills in its face.