Hedgehog quills are made of keratin, which is the same material as human hair and nails. The spines are around 2-3cm in length and an adult hedgehog has between 5,000 and 7,000 spines on its body. Hedgehogs shed their spines over time, with new ones growing in to replace them, just like our hair. Hedgehog spines are used purely defensively, and they will give a nasty jab to anyone who tries to penetrate the balled-up hog.