The Bark Eater


Last week, on day one of a two-day tracking and wildlife sign workshop in New Hampshire, we came across the fresh tracks of a porcupine. Porcupines have a number of interesting adaptations for climbing trees, including long, curved nails and pigeon-toed feet, the latter being a key feature in identifying its track in the snow.I was surprised to see this sloth-like, slow-moving creature’s tracks leading out from the forest and across the middle of a large open field. It seemed to be heading directly toward a group of three apple trees in the center of the field, so I asked the instructor, “Do porcupines eat apples?”

My own experiences with this strange creature are limited to the winter seasons I spent teaching winter field ecology in the Adirondacks and living at the New Hampshire Audubon’s Willard Pond Sanctuary. During those months, porcupines could always be found in a tree—most often a hemlock—feeding on bark. In fact, the Mohawk name for the porcupine is a very Anglicized version of “adirondack” and translates as “bark-eater.” Adirondack also was a derogatory term used by the Mohawk to describe the Native Americans residing in the cold, mountainous region of northern New York.

The next day, we returned to the field and watched the bark-eater lumber across the snow to one of the apple trees, pick up a fallen apple from the ground, and, with the apple firmly wedged between its formidable incisors, climb up into the tree before consuming its snack.

Yes, porcupines do eat apples.

The porcupine has a very interesting distribution across the United States, Canada and northern Mexico. Most of its range includes coniferous forest. Not surprisingly, the animal nicknamed “bark-eater” is limited in its northern distribution to regions where trees are found, and not in the treeless tundra. However, its distribution in the United States includes some quite arid, hot sagebrush and desert shrub habitat extending through the Southwest and into Mexico.

What’s most unusual is its absence from large forested areas in the East: the entire Southeastern United States, including the Appalachians between Georgia and Virginia. They are found in New Jersey, New York and Connecticut, but not on Long Island. A colleague suggested that the absence of winter den sites in the form of rock outcrops might be the factor that has prevented them from inhabiting Long Island, but that wouldn’t explain their absence from the forested mountains of Virginia and the Carolinas.

Among the porcupine’s interesting adaptations are the stiff bristles on the underside of its tail that help grip the tree bark and aid both in climbing and descending. Once it had finished the apple, we watched the porky climb down, tail first, and it seemed to be feeling its way down and supporting itself at times with its tail.

Porcupines have what biologists refer to as a two-chambered mouth. The lips can close and seal off the mouth behind its large incisors, enabling the latter to go to work removing the outer, corky, non-nutritious bark without opening its mouth and losing heat in cold winter temperatures. This lip and mouth feature is shared with another large rodent, the beaver, enabling it grasp branches with its incisors and swim underwater with a closed mouth.

Although females generally have four nipples, field researchers report only single births in the wild. One of the leading porcupine researchers in North America is right here on Long Island: Dr. Uldise Roze of Queens College, CUNY.

Porcupines are mature at two years and can live up to 30 years in the wild. Their most well-known adaptation is their modified hairs that form long, hollow, barbed quills, 30,000 in total. These are located everywhere on their body except for the face, belly, inner portions of their legs, and the underside of their tail. When the animal is threatened, the quills become erect, protecting the porcupine from most predators.

Porcupines will not attack other animals but assume a defensive posture when threatened. They give three distinct warnings to potential predators: auditory (clacking their teeth together), visual (the white-tipped quills form a chevron across the back) and olfactory (via glands in the skin of the lower back). Once the barbed-tipped quill penetrates the skin and muscle, it can work its way deep into the body through muscle contractions.

There is one predator that specializes in preying on porcupines: the fisher. A member of the fierce, quick and agile weasel family, the fisher works on getting a good grip on the porcupine’s nose in order to flip it over onto its back, exposing its quill-free belly. Although the fisher is an adept tree climber, this feat is usually only accomplished on the ground. I once found fisher scat containing an intact quill! In some areas, fishers have made a noticeable impact on porcupine populations.

The quills have other important functions. Being hollow, they help insulate against the cold, and they enable the porcupine to float quite well. That’s something I’ve never seen: a porky swimming!

Porcupines have an interesting relationship with humans. Being very slow, easy to find and catch in the wild without special equipment, and weighing 10 to 20 pounds, some outdoorsmen used to look upon this species as an important survival food and left them alone. Others considered it armed and dangerous. And most people considered them a nuisance, noting the damage they could do to trees, plywood buildings, ax handles, canoe paddles, and vehicle tires, brake and hydraulic lines.

The latter is the result of their seasonal need for supplemental sodium, mostly in the late spring and early summer months, and is a function of their low nitrogen-high fiber diet. And that has resulted in many areas instituting bounties on porcupines.

New Hampshire did not repeal its bounty on porcupines until 1979. It was around that time when the fisher started making a comeback after its population was decimated by poorly regulated trapping and habitat loss.

It was fun to see this interesting creature and explore its winter habitat: the thick grove of eastern hemlock trees and jumble of rocky outcrops where we located one of its simple, unadorned dens, whose floor was carpeted with sweet, hemlock-scented pellets of wood: its scat.

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