What are the spikes on porcupines called?

The spikes on porcupines are called quills. They are modified hairs that are made of keratin, the same protein that makes up human hair and nails. Quills are typically around 1 inch long, but some can be up to 3 inches long. They are sharp and barbed, and can easily penetrate skin. When a porcupine is threatened, it will raise its quills and swish its tail to try to deter predators. If a predator does come into contact with a porcupine's quills, they can become embedded in the skin and cause pain, infection, and even death.