This is my dog.
She’s a sweetheart, but like most bird dogs she’s been bred to be rather – um – inquisitive. And thanks to that curiosity, last week she wound up looking something like this:
Astra met a porcupine. And it did not want to play with her.
Porcupines are one of the largest rodents living near my house in New England, second in size only to the beavers that keep themselves to themselves in the pond down the road. Not that I’ve ever seen a porcupine in the flesh myself – they’re mostly nocturnal, and I don’t go stumbling around our woods at night. But at this time of year, the porcupines are out looking for love. Searching for potential mates in the crisp fall air leaves them awake and active at odd hours, raising the chance that they’ll run into a potential predator (or an exuberant housepet).
Fortunately for them, porcupines have a phenomenal defense mechanism. Their backs are covered with quills -- more than 30,000 of them – long, hollow tubes armed with wicked barbs. One pat with a paw, one playful nip, and your dog looks like a pincushion.
A quill’s anatomy makes it a formidible weapon. Quills are modified hairs, and they’re shed easily when they’re touched. But where your own hair is made of a thin and flexible strand of keratin, a quill arranges its keratin in a tube, making it stiffer by the same principle that makes the tubes in a bicycle frame sturdier than cables containing the same amount of metal. Run your fingers over your head, and you can feel your thinner, more compact hairs bend away. Tubular quills resist bending, and where your hair is pushed away at a touch, a quill is likely to push back.
And pushing back usually means pushing in. The end of a quill doesn’t just have one barb at its tip: it’s covered with tiny overlapping barbs that point backwards like rows of wicked teeth. Those barbs tear into skin like a serrated knife blade, concentrating penetration forces at each tiny point to shred through structural proteins. It sounds violent, but probably makes a cleaner cut than a smooth blunt quill could. But it makes the quills something of a challenge to remove. Pulling a quill backwards spreads out its barbs and anchors them firmly in flesh. And the barbs’ cutting action means that embedded quills can continue to migrate through the quilled animal’s body.
Which is why I didn’t take the time for a real photo of my dog plus quills. We were at the vet 10 minutes after her accident. Our vet had them out in about 15 minutes. And we'll be walking on leash until porcupine mating season is over.
Cho et al. 2012. Microstructured barbs on the North American porcupine quill enable easy tissue penetration and difficult removal. PNAS: www.pnas.org/cgi/doi/10.1073/pnas.1216441109
Johnson et al. 2006. Porcupine quill injuries in dogs: A retrospective of 296 cases (1998–2002). Can Vet J. 2006 July; 47(7): 677–682.
Vincent, J. F. V. 2002. Survival of the cheapest. Materials Today 5: 28-41. http://www.sciencedirect.com/science/article/pii/S1369702102012373