Some adaptations serve for defense. The Canadian porcupine is well-prepared with a large number of sharp quills, which are especially well developed on the animal's back, sides and tail. The quills can easily come off and fasten themselves to the attacker. They are very difficult to pull out. Some defensive devices enable animals to escape the attention of their enemy. The wings of the Dead Leaf butterfly, for instance, look very much like dead leaves. This makes it hard for the enemy to recognize it.