The Problem of Porcupines

Illustration by Adelaide Tyrol

By ordinary human standards, porcupines have many bad habits. Besides extricating their quills from the noses of pet dogs and livestock, humans must throw out axe handles and leather harnesses chewed beyond use. Porcupines damage, and sometimes kill, trees by gnawing on them; they even gnaw at uninhabited wooden buildings. The human response to porcupines is often an attempt to eradicate them by shooting, trapping, or poisoning.

This wasn’t always so. Among Native Americans in northern New England and elsewhere, the porcupine was prized for its quills, which were dyed and used in decorative work. In winter, especially, porcupines were an important source of meat—honored, along with animals such as deer, for their life-giving qualities. Though porcupines were common in the forests, their numbers were held in check by their main predator, the fisher.

Eventually, Native Americans began to hunt fishers for their fur. Then European colonists further depleted fisher populations by trapping them and deforesting the southern part of their range. With a scarcity of natural predators, porcupines have flourished throughout New Hampshire, Vermont, Maine, and eastern Canada.

Given the porcupine’s unique defense system, it’s easy to see why most predators leave them alone. As naturalist Paul Rezendes notes, the porcupine’s scientific name—Erethizon dorsatum—translates as “the animal with the irritating back.” While they appear prickly at all times, porcupines actually have a soft brown undercoat and coarser, longer guard hairs tipped with white that cover the quills. Fully grown, a porcupine weighs between 10 and 15 pounds and has 30,000 of these hollow, tapering, barb-tipped quills. Longest on the back and tail, the quills are raised when the porcupine senses danger, pushing the guard hairs forward to form an intimidating crest.

Approached by humans or other threatening animals, porcupines prefer to scurry away and climb a tree. Failing this, they will try hiding their faces and bellies—which have no quills—and presenting their backs. As a last resort, they release as many as several hundred quills by slapping an invader with their quill-studded tails. Embedded in flesh, the barbs will swell, driving the quills in deeper and making them difficult and extremely painful to remove.

No one seems surprised to learn that porcupines are mostly solitary animals. Near-sighted, slow-moving, they make their dens in rock ledges or hollow trees close to a good food supply. In our region, hemlock is a favorite food source and the mainstay of the porcupine’s winter diet. Although they don’t hibernate, porcupines curtail their activity and their range during the winter, never venturing far from their dens. Porcupine dens are easiest to spot in winter, when there will be large accumulations of scat around the entrances and hemlocks with partially stripped branches nearby.

The sedentary winter is the gestation period for the single porcupine offspring that will be born in April or May, its parents having enjoyed an extremely brief, if sweet, courtship in late October or early November. At the age of one or two, the female will go into heat for 8-12 hours, attracting the attention of males who follow her around, grunting and humming. Once she chooses her partner, the female engages in a kind of dance with him. Standing on their hind feet, the male and female embrace, placing their paws on each other’s shoulders and rubbing noses, whining and grunting all the while. They may cuff one another playfully before eventually falling to the ground, when the female obligingly flattens her quills and moves her tail out of the way. Once they have mated, the porcupines go their separate ways—despite their previous displays of affection.

Winter might be considered their “social season,” for porcupines are likely to group together in the choicest winter denning areas. Although they ignore each other, except for teeth-chattering over disputed food, as many as 100 porcupines have been found in large rock piles, and six were discovered living in an abandoned house in New Hampshire.

Believed to chew wood and leather for the salt left in it from perspiration, porcupines also need to hone their continuously growing teeth, which may explain why they gnaw at buildings. While tools can easily be stored out of a rodent’s reach, what about the damage porcupines do because of their appetite for the bark and buds of sugar maple, birch, white pine, hemlock, and fruit trees?

People can protect their orchards and plantations with electric fencing or by installing a 30-inch band of sheet metal or aluminum flashing around the base of individual trees. Liquid repellents available at hardware stores can also be brushed or sprayed on trees and buildings. If this seems like too much trouble, maybe it’s time for a change of attitude. As a biologist once told me when I complained about cluster flies, “You just have to appreciate biodiversity.”

Catherine Tudish is a freelance writer living in Strafford, Vermont.


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