Porcupines are rodents with a coat of sharp spines, or quills that protect against predators. The term covers two families of animals, the Old World porcupines and New World porcupines. Both families belong to the Hystricognathi branch of the vast order Rodentia and display similar coats of quills, but they still are quite different and are not closely related.
The Old World porcupines live in southern Europe, Asia and most of Africa. They are large, terrestrial, and strictly nocturnal. In taxonomic terms, they form the family Hystricidae.
The New World porcupines are indigenous to North America and northern South America. They live in wooded areas and can climb trees, where some species spend their entire lives. They are less strictly nocturnal than their Old World relatives, and generally smaller. In taxonomic terms, they form the family Erethizontidae.
Porcupines are the third-largest of the rodents, behind the capybara and the beaver.