A few years ago my friends' dog got nailed by a porcupine. We wrapped her in a blanket and pulled a dozen quills out of her mouth and muzzle, but we missed one in the roof of her mouth. We discovered it a few weeks later when it came out by itself... on the other side. The quill migrated all the way through her muzzle and emerged point first.
Porcupine quills have microscopic barbs that do more than make them stick in the skin of an attacker; they cause the quill to work itself deeper into the victim. Porcupine researcher Uldis Roze noted similar experiences with migrating quills, including one that worked its way through his arm. Roze was astonished - not by the quill's action, but by what didn't happen. There was no infection. Curious, he investigated, and discovered that quills possess antibiotic properties.
Porcupine quills are coated with fatty acids that give the quills a greasy feel.
Extracts of quill fatty acids strongly inhibited the growth of six bacterial strains.
Roze suggests that porcupines benefit from antibiotic properties because they commonly quill themselves. Although porcupines are good climbers, they seek precarious places because they favor the leaves and buds at the ends of branches and the tops of trees. Roze examined 37 porcupine skeletons and found that one-third had suffered fractures from falls, and he commonly saw falling-related injuries in porcupines he studied. Roze suggests that quill antibiotics may limit self-injury suffered in such falls.