Mammals' quills and prickles are types of hair but may be very hard and sharp. Some porcupines have quills up to 40 cm (16 in) long. A Canadian porcupine has about 30,000 quills each up to 12 cm (5 in) long. Put end to end, they would reach a third of the way up Mount Everest. When attacked, a porcupine charges backwards and sticks its quills into its enemy. As it moves forward again the quills are left behind causing serious wounds.