Trailing Porcupine at Dunby rd
Porcupine trail heading towards the camera. Note the urine along the midline, and the trail leading right to the base of the Hemlock tree and then turning away.
The Earth Tracks tracking apprenticeship had been trailing a few different species when I ended up a little ahead of the group. I was following a clear Coyote (Canis latrans) trail when I came to another trail in the snow. This new trail appeared to come from a hill to my right, crossing over the Coyote trail and then meandered through a small low spring fed clearing where while mostly covered in snow, some spots were open shallow puddles with Watercress (Nasturtium officinale) growing. On the other side of this patchy wet area, there was another hill thick with wide trunked Eastern White Cedar (Thuja occidentalis) and Eastern Hemlock (Tsuga canadensis) where the trail led upwards. I knew who this new trail belonged to pretty much right away due to the oscillating midline that ran through the length of the furrowed trough in the snow. Other clues were the trail width, which averaged out to about 15 cm (5⅞ in), and the occasional spotting of urine that was sprinkled intermittently along the run. This was the trail of the North American Porcupine (Erethizon dorsatum), a common fixture in the forests of Dunby rd.
I had been thinking a lot about Porcupines over the previous few days. We had encountered some chews on a Tamarack (Larix laricina) with one of my adult programs at the Guelph Outdoor School, and had followed a trail through a lowland Cedar forest along the Eramosa River. Porcupine ecology had been front of mind and I had a few questions already before following this new trail, and of course they were renewed with each new finding. When folks from the apprenticeship decided that we should follow and focus on the trail more fully, I was all in.
I took some measurements of the strides of the Porcupine, and they came in with an average of 21 cm (8¼ in), which was pretty much average based on some of the books and what I have seen so far tracking Porcupines. Most of what I could make out on the trail appeared to be a direct register walk, with the hind feet landing in the spot where the fronts had just been moments before, though I did find a lot of the trail to be nondescript due to the fluffy loose snow. The trail seemed to both meander and appear like the Porcupine was going someplace specific. If I were to interpret the trail in my limited understanding, it would be that the Porky knew the forest, but was also looking for something along the way; A new tree? A conspecific friend, family member or mate? According to Donna Naughton’s tome Natural History of Canadian Mammals (2012), the Porcupines breeding season is between September to November, with a possible second heat, if the first was unsuccessful, stretching the season to December, possibly even January. With this broad period of time to be mating, it could’ve been that the indivdual we were following was looking for a mate, but they may well have also been just looking for something to eat.
According to Porky researcher Uldis Roze (1989), Porcupines tend to choose a preferred tree species and stick with it. Maybe it’s a Hemlock, or a Cedar. Maybe Sugar Maple (Acer saccharum), Trembling Aspen (Populus tremuloides), or American Beech (Fagus grandifolia). It appeared to Roze when observing the trails of a few different individuals that they appeared to have preferences, and these preferences were distinct among the individuals. For example, one Pricklepig (another common name) only tasted and fed on 17 Beech trees along their trail though the trail also encountered 37 Sugar Maples, 27 Hop Hornbeam (Ostrya virginiana), and 6 White Ash (Fraxinus americana). Another individual’s trail recorded a year later counted 7 Sugar Maples singularly fed on in a line that also included Red Maple (Acer rubrum), Striped Maple (Acer pensylvanicum), Mountain Maple (Acer spicatum), Hop Hornbeam, Beech and White Ash. These two individuals appeared to demonstrate individual taste and preference for specific species in their given habitat. Perhaps the Porc-épic (french common name) I was trailing was looking for their favorite flavour in the forest? The trunk in the photo above is of a Hemlock tree, but I wish I had noted every tree they had stopped to investigate.
I continued along following the trail and with most of the rest of the crew ahead I figured I could take it slow and inspect whatever I came across. Lucky for me, I came across a small narrow woody object in the middle of the Gaag (Ojibwe name, pronounced “ga’awg”) trail. When I bent to look, I realized it was scat!
The scat appeared different than I had seen in person before, but similar to some images I have found online and on some study calls. To my eyes it looked like three pellets stuck together with a mucousy coating. When I looked close at the content it looked like disorganized masses of pale brown wood chips. I didn’t take any notes but I remember the scat being about a 1 cm (⅜ in) in diameter. I don’t remember the length of the whole string, but from my photos I would guess at 7.5 - 8 cm (3 - 3⅛ in). I didn’t smell the scat, but I wonder now at if it would have helped me to identify the contents better?
I carried the scat with me as I walked along in hopes to show the rest of the group. I left the trail I was on, noting first where it went, and then sped up then to meet up with the group. Turns out everyone was just ahead of me staring up into a Hemlock tree where a Porcupine was resting in the upper branches. I didn’t really pay attention to this Porcupine much because the group mentioned that the trail I was just following led to another tree, a very large Maple a little ways down the hill. I had noticed this tree as the trail I was on previously was leading toward the Maple rather than the Hemlock where the group was standing. I handed off the scat and made my way towards the Maple.
The Maple was pretty large. Very tall with a fairly wide trunk. There were a couple of Tinder Polypores (Fomes fomentarius) growing above a large hole in the trunk, with a lot of human tracks around the base. In the snow just in front of the hole there was a pile of Porcupine scat which appeared stepped on by boots and compressed into the snow a little. I took some photos of the scat in the tree cavity and then turned on the front facing camera, reached my phone in and pointed it upwards. The first shot was dark and blurry, but once I turned on the flash I was not disappointed.
Looking at my phone I could see that there was a Porcupine hiding out, tucked up inside the bole of this huge Maple. I have seen this behaviour a few times, but I always find it pretty endearing. Especially when I looked close and saw part of the heel of the Porky’s right hind showing like the bottom of my slippers at home. It was a cozy nook for this gentle rodent to pass their time. I have since read that the Winter den sites are usually pretty close to their preferred feeding trees, so finding this other individual so close to the big Hemlock with the first Porcupine made sense. Perhaps they share this den? I have read that North American Porcupines are pretty solitary, but have also witnessed many denned up in the same den a few times. I quickly got up and away from the Maple immediately and made my way back to see the other Porcupine in the Hemlock tree.
Over the past 10 years of noticing and watching Gaagwag (Ojibwe again, but pluralized this time) I have seen many instances of them hanging out in and feeding on Eastern Hemlock trees. I can relate with my own appreciation for the Hemlock trees. I love their beauty, their ecology and their taste, both straight from the tree, or especially, in tea. I find the flavour to be piney with a whisp of fruit, sort of citrusy, and warming, and I am incredibly grateful to the Porcupine for their help in retrieving the needles for my teas. I’m just piggybacking on some of the baseline behaviours of the Porky. Since the bark of the Hemlock is high in tannins, the Porcupine feeds almost entirely on the needles and twig tips which contain fewer tannins. They nip the terminal branches and pull them in, eat the leaves and drop the branch. If any leaves remain on the dropped twigs which have fallen to the ground, they are often consumed by White-tailed Deer (Odocoileus virginiana) or by weird naturalists who like to make Hemlock tea.
I had a question about the quality of the forage. Do Hemlock branches really have that much nourishment? I recognize that Hemlock needles contain high vitamin C, but that isn’t enough to survive on, especially throughout the coldest hardest season of the year. What do the Porkies get from the Hemlock? In the book “Porcupines: The Animal Answer Guide” by Uldis Roze (2012), he writes that “Winter foods available to the North American porcupine contain less protein, more fiber, and more plant defense compounds (toxins to deter herbivory) compared with [S]pring and [S]ummer foods. As a result, [P]orcupines lose body weight and deplete stored fat layers”. Imagine that! You’ve gotta eat as much as you possibly can throughout the Spring, Summer and Fall so that when Winter comes, you don’t die because the trash you eat doesn’t provide enough actual nourishment to sustain you (I feel like this between Christmas and New Years sometimes). What a rough go. But the Porcupines have an advantage though; their caecum. What’s a caecum, also spelled cecum, you ask? A caecum is a section of the digestive tract at the junction of the small and large intestines where food that has been eaten ferments and bacteria and fungi breaks down the cellulose and lignin from plant materials a little more. This fermentation process helps pull out more nutrition and energy from the roughage that the Porcupines are consuming. Humans, lagomorphs, some birds, and even Lungfish have cecums, though they are not found in amphibians. For different species the cecum are shaped and function differently. For humans they are relatively small and connected with the appendix.
So the caecum helps break down the weakly nutritious fodder a little bit more to turn it into something a bit better. That helps a bit through the toughest time of the year.
Another neat thing to look for on the twigs dropped by Porcupines is the conspicuous angle of the cut which remains on the proximal end of the twigs. This distinct angled cut with characteristic “steps” which can be found on twigs nipped by both rodents (the family which Porcupines belong) and lagomorphs (rabbits, hares and pikas). Some folks call this a 45° cut, but it isn’t always though it sure comes close. Just knowing this angled cut and keeping an eye out can help us start to narrow in on who cut the twig.
This brings up a question for me.. what are the mechanics of Porkies eating? What are the teeth doing exactly? I have read that when Porcupines are feeding on cambium on a tree, they anchor in with the upper incisors while swinging their jaw and scraping with the lower incisors. This is the method for chewing the cambium, but not necessarily for the nipped twigs. What do the Porkies do to get the angled steps of the nipped twigs? This is going to require a little more research on my end as I can’t seem to find anything as of yet. Perhaps I’ll go out in the Spring and try a sit spot beside some Porcupines and see what I can sort out.
Lastly, it seems like some of my other questions don’t seem to be answered in the literature, like does the astringency of a bark, namely Hemlock with their high tannic content, change the scent of the Gaag’s urine? Maybe the researchers just aren’t as interested in urine as much as I am, but that’s a whole other blog post.
It has been a lot of fun to reflect on Porcupines over the past month, considering the part they play on the land and how they play that part. They are large, lovely and seemingly more abundant than they have been in the past - perhaps as more forests grow back in Southern Ontario, replacing the farmland which replaced the forests originally, then we’ll see more and more of the North American Porcupine.
To learn more:
Mammal Tracks and Sign by Mark Elbroch and Casey McFarland. Stackpole Books, 2019.
Natural History of Canadian Mammals by Donna Naughton. Canadian Museum of Nature and University of Toronto Press, 2012.
The North American Porcupine by Uldis Roze. Smithsonian Institution Press, 1989.
Porcupines: The Animal Answer Guide by Uldis Roze. Johns Hopkins University Press, 2012.