It’s not easy being a female porcupine. You mate in the fall and are either pregnant (7 months) or lactating (4 months) for the next 11 months before you have one month’s break and begin this cycle all over again. This time of year porcupines are giving birth to one young that is covered in fur and quills and weighs about a pound. The young porcupette is born headfirst in a sac, in order to protect the mother from quill damage. Its quills are soft at birth, but harden within an hour. (Thanks to Kay and Peter Shumway for photo op.)
At least one porcupine got a jump on humans this sugaring season. A porcupine eats outer tree bark in order to access the phloem (layer of inner bark cells that transport nutrients) and cambium (produces phloem and xylem cells) layers of a tree, its primary winter diet. In eating these layers, the porcupine unintentionally cuts into the xylem, or sapwood, where water and dissolved minerals (sap) are transported between the roots and crown of the tree. Unintentionally, porcupines tap the trees whose phloem and cambium they eat. In this case, the weather had warmed up enough to cause pressure in the tree, which in turn caused the sugar maple’s sap to flow just as a hungry porcupine happened along. Soon thereafter, the temperature dropped, causing the sap to freeze, forming icicles. While they looked good enough to sample, one whiff of them told me that sap was not their sole ingredient! (They were located beneath the porcupine’s den in a hollow tree, from which urine flows freely.)
A recent exploration of some rocky ledges, a favorite winter denning site of porcupines, revealed a virtual maze of trails leading to roughly a dozen crevices where porcupines sought shelter. A look inside these crevices confirmed that porcupines leave something to be desired when it comes to keeping house. Unlike many other animals that keep their dens pristine (e.g. beavers only defecate in water, never in their lodge), porcupines don’t feel the necessity to roust themselves when nature calls. As a result, the floor of their den consists of years of accumulated scat (and urine). In some cases, the pile of scat in these ledge dens was so high that it made you wonder how a porcupine could even fit into the crevice, and indeed, in some cases, porcupines do have to dig their way out of their den. When it became aware of my presence, the pictured porcupine assumed its characteristic defense posture, exposing its quill-filled back and upper tail surface to the intruder. It needn’t have worried, as the opening was barely wide enough to get the camera into, much less the photographer!
It’s fairly obvious when there are active porcupines in the woods, as they leave all kinds of signs. The females, who often spend the day in a hollow tree or rock den, come out at night to eat (males often spend several days up in a tree), and leave very pronounced 6” – 9” trails back and forth to their feeding trees. Along this trail, in addition to an occasional quill, there are often pellets of scat as well as urine, which both your eyes and your nose can detect. Porcupines discard the tips of hemlock branches when they’re through eating the tender buds and leaves up in the canopy, and consequently the ground under a feeding tree is often littered with “nip twigs.”
Contrary to their name, fishers seldom eat fish. While they prey on a wide range of animals and even plants, their preference is for small mammals (80% of their diet), snowshoe hares and porcupines. Because fishers are well equipped to kill porcupines, and because there is little competition for them, porcupines are an important prey of fishers –up to 35% of fisher diet samples contain the remains of porcupines, as this photograph of fisher scat attests to. There is no mistaking the bumpy porcupine foot pads (and quills)!
Given the amount of time porcupines spend in trees, it’s not surprising to see that their feet are well adapted for climbing. Long, curved nails that grip the bark, as well as “pebbly” foot pads designed to prevent slipping allow this prickly rodent to climb just about anywhere it wants to. (Hind foot pictured.)
Porcupines leave plenty of signs where they have eaten the inner bark, or cambium layer, of a tree. Bark is missing on the trunk of the tree, leaving fresh, yellow wood exposed, which often bears incisor marks. An observation I have made over the years is that porcupines often de-bark around or near their hollow tree dens. Typically, if a tree den is used year after year, they gnaw off bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells. This has led me to wonder whether fresh de-barking in the vicinity of their tree den entrance might have more, or as much, to do with a porcupine’s staking out a claim on that tree than with its sustenance. I have never come across any research that even mentions this phenomenon, and would welcome feedback from anyone who has.
Typically, male porcupines spend days at a time up in eastern hemlocks, eating the tender buds and leaves of branches, while females tend to spend the day in a den, and head for nearby food at night. In the photograph, a porcupine den tree is on the left, with scat from the den having fallen on the snow below. The trail you see was made by the porcupine, as she went from her den tree to a nearby feeding tree. Usually a den is chosen within a short distance of food, as was this one. If you look closely at the uppermost quarter of the photograph, you will see a sign that indicates recent porcupine activity – nipped hemlock branches in the snow, that have been discarded by a porcupine, who’s feeding in the branches up above them. It’s much safer to remain on a large limb and pull the desired tip of a branch in to you than it is to attempt to climb out on a thin branch. Once the porcupine nips the tip of the branch off and eats the tender buds and leaves, it drops the branch to the ground below.