To Quill or not to Quill
You may have heard about porcupines. They are dim-witted, forest-destroying pests who throw their quills and serve no useful purpose. But is this truth or fiction?
Don’t mess with me!
First, let’s dispense with the myth that porcupines1 can throw their quills like tiny spears—they can’t. They can flick their quill-studded tail rapidly back and forth, driving their needles into the flesh of a would-be predator or an inquisitive dog. Simply put, they cannot fire their quills no matter how much they may wish to.
I first experienced the after-effects of a porcupine encounter with our dog Maia. My wife, Zoe Weil, brought her and her mouthful of quills into the veterinary clinic where I worked. Hundreds of dogs with tens of thousands of quills were to follow Maia into the clinic over the years. Over time, I developed a fascination with porcupines and their ways of defending themselves.
Adult porcupines are the second largest rodent after beavers who are native to North America. They weigh on average 10-25 pounds and live up to 18 years. Porcupines are mostly nocturnal, strict herbivores with large, ever-growing, chisel-like, incisor teeth. These tools allow them to eat a large variety of plant material including the nutritious inner bark layers of trees. This habit doesn’t endear them to those who grow trees, however there is little evidence that porcupine damage has widespread, negative ecological effects. Conversely, dead trees in a mature forest provide necessary habitat for a large variety of wildlife.
Quills, quills and more quills
The porcupine’s scientific name is appropriately, Erethizon dorsatum, meaning “irritating back” since quills are topside on the porcupine and absent from their belly. Some predators like the fisher, Pekania pennanti, take advantage of this feature by attacking their underside.
Porcupines have a patch of skin on their rear end called the rosette. It has large numbers of quills and emits a strong odor. Porcupines orient the rosette toward an attacker when threatened. So, if you come upon a porcupine and she only allows you to see her rear then you are perceived as a threat.
“Life is too short to have boring hair.” – Unknown
Quills are probably their most noteworthy feature, but porcupines actually have 5 types of hair—yes, quills are modified hairs. They have whiskers on their heads for sensing their environment; long, thin guard hairs for protection and tactile information about their surrounding; fur for insulation; bristles on the underside of their tails to assist in tree climbing; and, of course, quills. Petting porcupines is possible if you pet them in the right direction (head to tail). Captive, tame porcupines seem to enjoy it, but their quills are not soft, and they can’t compete with dogs for providing a pleasurable petting experience. I don’t encourage the practice.
A porcupine may have up to 30,000 quills, each of which can easily penetrate the skin of an attacker, yet they are difficult to remove due to the reverse-pointing scales on the tips.
As an aside to people with dogs: if your dog encounters a porcupine, don’t cut the ends of the quills off in the mistaken belief that this will let the air out and deflate the quills making extraction easier. The inside of a quill is sponge-like and won’t deflate when cut. Cutting the quill will make it more likely to break off and be harder to remove.
Live by the quill, die by the quill?
Imagine wearing a coat of thousands of barbed spines—surely you’ll stick yourself by mistake during a fall, and when breeding2 or fighting. Not surprisingly, porcupines have been seen with embedded quills. However, they have also been observed grasping and removing them with their claws. If you’re covered by 30,000 quills it’s a good idea to know what to do if you stick yourself by mistake.
As additional protection against self injury, fats on the porcupine’s skin may act as antibiotics. These fats may help prevent infection when a porcupine “quills” himself.
I have found in the woods the remains of a predator with embedded quills. I’ve also seen vultures with quills in their faces. So, quills don’t offer a guaranteed deterrent, and there are some animals who prey on porcupines, including fishers, coyotes, and lynx. Porcupines are primarily arboreal which is additional protection against some predators, although fishers are very agile on the ground and in trees. They have even been reintroduced to some locations where they had previously been eliminated to serve as natural controls on porcupine populations.
Ah, the tree life!
A running porcupine is a contradiction in terms—at best they manage a fast waddle. By contrast, they are very adept in trees where they defy gravity and venture out on the smallest twigs in search of food as well as to build occasional nests. However, this boldness has consequences, and up to 30% of porcupines have been found to have healed fractures, apparently from falling out of trees.
They breed in the fall and overwinter in dens under rocks, in tree stumps or other protected sites, and their characteristic tire-like tracks can often be found in the snow leading to their dens. Pregnant females give birth in the spring to a single porcupette3 who, thankfully for the mother, has soft, flexible quills that harden within a few hours of birth to serve as protection.
The answer to the ultimate question of life, the universe, and everything is 71
1 The quills and skull were found in the woods by me or collected by our dog, Herschel.
2 Breeding while wearing a coat of quills requires careful coordination between the male and female.
3 Yes, baby porcupines are called “porcupettes”.
4 Apology to Douglas Adams and The Hitchhiker’s Guide to the Galaxy
5 See for example,