The porcupine is a rodent that is covered in sharp spines. These spines are used to protect the porcupine from predators. When a predator tries to attack a porcupine, the porcupine will turn its back to the predator and raise its spines. The spines are so sharp that they can easily penetrate the skin of a predator. This makes it very difficult for predators to kill porcupines.