Photo: Uldis Roze

Animals and Plants of the Finger Lakes

The Prickly Porcupine

You probably won’t see them, though you may detect signs of their presence.

Anything containing sodium and left outside overnight may be destroyed by gnawing teeth: wood siding, painted signs, truck undercarriages.  You may notice “witch trees” whose branches are stunted and twisted from years of browsing.  You might even come across the animal’s distinctive wavy track in the snow, created by a waddling gait and a heavy, dragging tail, or smell its turpentiney urine.  And if you look up while walking through the woods in the winter or early spring, you might catch a glimpse of the porcupine itself doggedly feeding on bark or buds, looking for all the world like a squirrel nest on the move.

Photo: Uldis Roze
Photo: Uldis Roze

The porcupine (Erethizon dorsatum) is the second-largest North American rodent, surpassed in size only by the beaver; it may be up to two feet long, not including the tail.  Unlike its sleek cousin, it looks permanently disheveled, as if it’s just been rudely awakened from sleep.  Nevertheless, it is exquisitely adapted to a life high above the forest floor.  Its extremely thick fur offers excellent insulation against harsh winter temperatures.  Its feet have a single footpad covered with pebbled skin much like the surface of a basketball, as well as very long, curved claws that hook into even the tiniest crevices.  On the underside of its tail are short, backward-pointing bristles that act as crampons.  Since they spend most of their lives pressed against trees, porcupines have no quills on the belly, and no external genitalia.

In contrast to the social and proverbially energetic beaver, the porcupine is nocturnal, solitary, and does everything, including reproducing, very, very slowly.  Native Americans revered the animal because it so often saved them in times of famine; it is so confident in its quills, and so slow, that it can be easily clubbed to death.  Today, the porcupine’s worst enemy is the automobile.  Many are killed each spring on highways where they congregate in order to feed on road salt.  Coyotes, mountain lions, and owls have been known to eat porcupines, but their only specialized predator is the fisher.  This weasel-like animal attacks the porcupine’s head repeatedly until it is wounded and disoriented, then flips it on its back.

The porcupine’s warning system, like the skunk’s, uses black and white, the colors most easily seen by nocturnal predators.  A black stripe runs down the length of its tail and white quills bristle from the sides; the quills contain a fluorescent pigment that makes them seem even brighter.  If an animal ignores this message, the porcupine will chatter its teeth, release a warning odor, erect its quills in all directions, and swing its tail like a mace.  The quills, which can be up to four inches long, are coated with tiny barbs; under an electron microscope, they look like the fringed trunks of palm trees.  On impact, the quills loosen from the porcupine’s skin and lodge in the attacker’s flesh, and muscle movements gradually draw them inward.  A predator may be killed by a quill that pierces a vital organ or makes it impossible to eat, but it will probably not die from infection.  Quills are coated with grease that facilitates penetration but also has antiseptic properties.  This adaptation is designed not to spare the porcupine’s predators but to protect itself.  Porcupines live dangerously, venturing out onto slender branches in order to feed; they often fall from great heights and impale themselves on their own quills.

Official maps show that porcupines are present in every corner of upstate New York, but in fact they seem to be uncommon in the Finger Lakes.  They are found regularly in the Southern Tier, including the Land Trust’s Parker, Plymouth Woods, and Steege Hill preserves, in the Connecticut Hill area, and they have recently been spotted in the town of Danby, Tompkins County.  However, there are many areas of what would seem to be prime porcupine territory that are apparently unoccupied.  Perhaps habitat fragmentation is partly to blame; the porcupine will not readily venture into open areas in order to cross from one forest block to the next.  In addition, the arrival of two new species may make life even more tenuous for the porcupine.  The fisher is making a comeback in the region, and the woolly adelgid, an invasive insect, is wreaking havoc on the hemlocks that provide food and shelter for porcupines in the winter.  The sight of a porcupine high in the trees, never common even at the best of times, may become even rarer.

This story by Jacqueline Stuhmiller first appeared in our newsletter, The Land Steward, as part of the Closer Look series.

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