A porcupine is a type of rodent native to parts of Asia, Africa, North and South America and Italy. Porcupines tend to live in temperate climates and are characterized by their coat of spikes or quills. In fact, their name makes reference to this feature, as porcupine is derived from Old French porc d'espine, meaning "spiked pig."
There are 330 species of porcupine, and they may be brown, grey, or, rarely, white. Porcupines have tails measuring about eight to ten inches (20-25 cm) and a round body weighing anywhere from 12 to 60 pounds (5-27 kg). Most are slow-moving, but some varieties in the Americas are agile climbers. There are two basic types of porcupine: the so-called Old World and New World varieties, characterized by the hemisphere to which they are native. The two branches of the porcupine family are actually not closely related, and their quills are not inherited from a common ancestor, but rather an example of convergent evolution, meaning both groups developed the trait independently.
Old World porcupines are mostly terrestrial, meaning they live on the ground, and are quite large. The Crested Porcupine of North Africa and Italy is the fourth largest rodent and can weigh as much as 60 pounds (27 kg). New World porcupines are much smaller, and many varieties live in trees. One exception is the Common Porcupine of Alaska, Canada and the Northern United States, which is terrestrial and weighs up to 40 pounds (18 kg). The two branches of porcupines also differ in that Old World porcupines have quills grouped in bunches, while New World porcupines have individually attached quills. Neither variety of porcupine can throw their quills, although it is a common misconception that they can.
The quills of porcupines are modified hair shafts that evolved as a defense against predators. While the porcupine shares this trait with the hedgehog, the two animals are not to be confused. Unlike the porcupine, the hedgehog is not a rodent, but an insectivore.