Porcupines' quills, or spines, take on various forms, depending on the species, but all are modified hairs coated with thick plates of keratin, and embedded in the skin musculature. Old World porcupines have quills embedded in clusters, whereas in New World porcupines, single quills are interspersed with bristles, underfur, and hair. Quills are released by contact or may drop out when the porcupine shakes its body. New quills grow to replace lost ones.
- Approximately 30 quills per bag