Does walking and climbing softly while carrying 30,000 barbed quills imbue porcupines with their steady manner?
LOOKING UP during a winter wander, I often spot our Buddha of the East, the slow and placid porcupine (Erethizon dorsatum), gazing calmly down from a treetop. In a world with no tires, highways or people, porcupines might well grab life by the tail and rest on their quills. They are amazingly adapted creatures.
The second largest rodent native to North America—after beavers—porcupines waddled north from the South American tropics at least 2.5 million years ago. Presently distributed from coast to coast and north to the tree line, porcupines have yet to reach Newfoundland, Prince Edward and Cape Breton.
An average adult porcupine weighs 4.5 to 7 kilograms, measures 75 centimetres long, lives for 15 years and swims well, with its buoyant quills, so reaching islands may be just a matter of time. Unable to see well beyond a few metres, they nevertheless are able to detect movement farther afield; their senses of touch, taste and smell are better refined.
Porcupines climb up trees head first, and descend tail first, but they lack agility. That clumsiness sees them falling out of trees, in spite of having strong claws and bare soles that are roughened with small knobs for a better grip. A study of porcupine skeletons that appeared in National Wildlife magazine in 1994 revealed that 35 per cent had healed bone injuries commonly associated with falling.
Any discussion about porcupines that neglected their quills would prove, well, pointless. They are equipped with five types of hair (including quills, which are considered a kind of hair modification). Those types of hair include bristles on the undersides of the tail for support while tree climbing; guard hairs that shed rain and snow; thick fur that insulates them from the winter cold (this fur is shed as spring arrives and grows back in the fall); whiskers that aid their sense of touch; and 10-centimetre-long quills on their back and neck, which can be raised to impale potential predators.
As some rural dog owners may already know, each quill is stiff, cylindrical in cross-section, and has a spongy core. Tips are needle-sharp and equipped with dozens of microscopic, backward-pointing barbs. When these barbed quill tips penetrate the skin of a hapless aggressor, the quills can go only one way—off the porcupine and into the victim.
Quills lost in skirmishes are re-grown in a matter of weeks. Their nose, throat and belly lack quills, a fact that a few predators use to their advantage.
These “reverse pincushions” have several natural enemies capable of penetrating that formidable armour. The fisher is one, a dark, two- to five-kilogram weasel-like animal that attacks by darting repeatedly into the porcupine’s face, delivering eventually mortal wounds. Other natural predators include bobcats, cougars and coyotes.
As a biologist I have learned first-hand about quills. When they penetrate, the quills’ spongy core absorbs body fluids, expanding to make the barbs flare. With each muscle contraction, the barbs drive the quill farther into the victim’s body. Tail quills are shorter and easily disappear under the skin.
Painful but unseen, one tail quill migrated from inside my hand to emerge from mid-arm a week later.
Quills rarely cause infection, something that probably evolved so porcupines wouldn’t die from their own impalement. Its flailing tail hits many curious first-timers—dogs, deer, beaver, foxes, owls and coyotes. Some learn, some don’t, others die.
In winter, porcupines like to den in a hollow tree. These are easily identified by the pile of droppings around the base. Most of the feeding takes place within 100 metres of the den site. Imbued with an uncanny ability to detect trees that offer more nutrients, porcupines use their large upper and lower incisor teeth to gnaw into and consume the inner bark and young twigs of eastern hemlocks, balsam fir, tamarack, white and red pines, eastern white spruce and red spruce. If the bark removal rings the trunk, the tree is girdled and it dies. However, the damage is typically restricted to a small percentage of the available trees and is rarely mortal. The unusual, twisted shapes that evolve as trees recover from the damage are often helpful to other wild species—for example, producing limbs that birds use for nesting.
In spring, the swelling buds of trees and their flower parts are eaten first; leaves are sought later as they emerge. Porcupines switch foods and trees as the affected trees react to their attack by producing bitter tasting tannins (compounds) in their leaves.
Porcupines also have a penchant for salt and, ironically, sometimes attack tires for the road salt smeared over them. This salt craving has some animals chewing into cabins, gnawing furniture and tools, even consuming plywood for its glue. In the wild they locate and avidly chew bones and antlers for their mineral content.
Most rodents are litter-prone, producing babies en masse; after maturing at the age of three, female porcupines bear only one youngster a year for the rest of their lives. Breeding occurs in the fall, really ramping up when the female climbs up a tree and emits loud sounds like those made by cats. Other noises include moans, screams, grunts and barks. This attracts males, and soon brutal fights erupt. Eventually a winner emerges, a suitor for whom she climbs down the tree. Mating occurs when she willfully arches her tail up and out of the way. Consent is an absolute must in the delicate issue of porcupine intimacy!
Baby porcupines are born in the spring. They are well-developed, with eyes open and black fur concealing quills that harden in a matter of hours after birth. The youngster stays with its mother, nursing for up to 130 days until it’s left on its own shortly before the fall breeding season.
I once shared time and space with a porcupine at my home in Pomquet, NS, while it grazed on the lawn on spring evenings. One day the neighbours came to visit when I was away. Thinking it was the right thing to do, they chased my friend away. On the ground, a porcupine’s slow-motion habit can erupt into a clumsy gallop. My prickly lawn buddy never came back.
A human friend has since befriended her local porcupines. After dark, they clamber up onto a planter outside her kitchen, taking apples carefully from her hand through an open window. Interestingly, they will eat organic apples, but refuse sprayed apples unless the skins have been peeled off. Now really! Who’s smarter here?