, Gloucester, MA

January 11, 2013

Prickly companion, the North American porcupine

Dave Sartwell

---- — The North American porcupine (Erethizon dorsatum for you Latin fans) is a slow-moving, large-bodied, short-legged rodent with a waddling gait that wanders through much of the wooded areas of Cape Ann. This much maligned little fellow is actually a very important part of the natural animal kingdom that surrounds us.

Although it looks awkward when walking on the ground, it can scale trees to great heights, climbing in a very slow and deliberate manner. You can often see them high above the forest floor, precariously perched out on tiny branches that seem extremely dangerous for such a fat little fellow. They can do this because their feet are uniquely structured for the task.

At the end of their paws they have very long and strong claws. They can use these to hook into the surface bark of the trunk of a tree and draw themselves along. Once they scale the tree, it is the texture of the soles of their feet that allow them to maneuver about. The soft, pebbly-like skin gives them not only a sensitive touch, but a gripping surface that allows them to hold on.

Once in the tree, the porcupine can hold on with just his back feet, using his tail as a tripod-like prop to hold himself in place. This frees his front paws up for use in pulling leaves, twigs and nuts in close for feeding.

They feed on a wide variety of vegetable matter based on the season. In the spring they love the buds of the sugar maple tree which contain high amounts of protein. However, because porcupines don’t deal with tannins well, they abandon the maples as soon as they start to leave out. In the summer they move on to eat the cambium of sapling beech, basswood, and other similar trees that have relatively low levels of tannin. In the fall they love apples, and nuts such as acorns and beech. In the winter they forage on trees like hemlock and sugar maple.

Nitrogen is a crucial resource for their nutrients. In the winter they can survive on foods with fairly low levels of nitrogen because the high-fiber food they ingest stays in their system a very long time, allowing them time to to absorb the nutrients. However, porcupines slowly loose weight all winter because of this.

Most people do not realize that porcupines feed mostly at night. This is because the plant and leaf metabolic process produces more nutrients then. Porcupines simply get more out of their groceries when they chow down after dark.

Porcupines are very good to eat. They were often viewed as a delicacy by Native Americans and early settlers. Coyotes, bobcats and fisher still eat them as a regular part of their diet. They have survived through the years by their one really effective defense mechanism---their quills.

Each porcupine is covered by as many as 30,000 very sharp, pointed quills. Each quill has thousands of overlapping, backward facing scales that look like shingles on the side of a house. The quill is not hollow, but filled with a spongy substance that makes them very rigid and very light. The hard point of the quill drives into the flesh of the enemy. The scales lie flat on the way in, but the warmth and moisture of the flesh of the wound make the scales flare open slightly and prevent the quill from being easily removed. In fact, the muscle contractions by the victim drive the quill in even further.

The porcupine cannot throw the quills from its body, but the quills come out easily when they come in contact with the flesh of its attacker. The quills are in constant production on the body, with the porcupine losing many every day. When attacked, the porcupine can also give off an odor not as bad as a skunk, but enough to be pretty disgusting.

The underfur that covers the body is very thick, like wool on a sheep. The strands are very closely packed in the winter, keeping this little fellow warm in extremely low temperatures. It keeps cool in the summer by shedding down to the skin. Early in the fall the new fur starts to grow back in. Fly tiers use this fur in many different patterns.

The porcupine mates once a year in October or November. The female, when ready, will attract many male suitors. These males will fight with an amazing ferocity, sometimes to the death, to determine which one will breed with her. A dominant male in a region will breed many females, but the female will only breed once with the male. In fact, the male will ward off any other suitors for several days to be sure.

About 210 days later the female will give birth to only one youngster. It will weigh in close to a pound and be about 10 inches long. The porcupette will nurse up to 4 months, but will be out of the den in just a few weeks. The mother hides the youngster on the ground during the day while she sleeps in a tree.

After about six weeks the baby will follow the mother to a feeding tree where it will wait at the bottom for food dropped down from above. Over the summer the youngster slowly learns to forage and climb. By October he is left on his own.

Unlike most animals, it is the young females that will leave the area to find their own spot to live. This is natures way of preventing inbreeding.

The porcupine will grow to 30-40 inches long and 12 inches high at the shoulder. It’s tail will average between 7-11 inches long. The average adult will weigh in at about 17 pounds, but some have been found in the 40 pound class! They can live in the wild up to eighteen years.