Hedgehogs have spikes to defend themselves.
I’ve never heard of or seen hedgehogs fighting. They are not aggressive animals or predators as such, although snails, slugs, beetles and other small insects upon which they feed may not agree with that statement. However, there are some animals such as foxes which would consider a hedgehog a tasty meal, so they have to have some other way of defending themselves. A coat made of spikes is an excellent way to keep away such predators. The spikes are actually specially adapted hairs and an adult can have between 5,000 and 7,000 of them on their upper body and back. They are hollow and flexible but quite stiff, so that when the hedgehog curls up tightly into a ball it becomes a ball of hard sharp points. Each spike lasts about a year, after which it drops out and a new one grows, just like human hairs. Read more about these really interesting creatures here.