Porcupines are rodents with a coat of sharp spines, or quills,
that defend them from predators. They are indigenous to the
Americas, southern Asia, and Africa. Porcupines are the third
largest of the rodents, behind the capybara and the beaver.
Porcupines' quills, or spines, take on various forms, depending
on the species, but all are modified hairs coated with thick
plates of keratin, and they are embedded in the skin musculature.