stress and is often seen with quill erection. If these processes fail, the porcupine will attack by running sideways or backwards into predators. A porcupine's tail can also be swung in the direction of the predator; if contact is made, the quills could be impaled into the predator causing injury or death. Quills 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. Despite what is commonly believed, porcupines do not have the ability to launch their quills at range. There are some possible antibiotic properties within the quills, specifically associated with the free fatty acids coating the quills. The antibiotic properties are believed to aid a porcupine that has suffered from self-injury. Uses by humans Porcupines are seldom eaten in Western culture but are eaten often in Southeast Asia, particularly Vietnam, where the prominent use of them as a food source has contributed to declines in porcupine populations. Naturalist William J. Long reported the taste of the North American porcupine as "vile" and "malodorous" and delightful only to a lover of strong cheese. With regards to a Maine state law that restricted the killing of porcupines to keep them available as emergency game for people lost in the woods, he noted: "It is undoubtedly a good law; but I cannot now imagine any one being grateful for it, unless the stern alternative were death or porcupine." More commonly, their quills and guard hairs are used for traditional decorative clothing; for example, their guard hairs are used in the creation of the Native American "porky roach" headdress. The main quills may be dyed, then applied in combination with thread to embellish leather accessories, such as knife sheaths and leather bags. Lakota women would harvest the quills for quillwork by throwing a blanket over a porcupine and retrieving the quills left stuck in the blanket. The presence of barbs, acting like anchors, causes increased pain when removing a quill that has pierced the skin. The shape of the barbs makes the quills effective for penetrating the skin and