Saturday, November 14, 2009

Porcupines: Armed and Dangerous

At the mention of the word “porcupine” most of us conjure in our minds the image of a medium-sized brown animal covered with long quills. But beyond this, I’d be willing to say that the average person knows very little about our second largest rodent, a relatively shy animal with poor eyesight, little muscle tone, and a fondness for salt. So, I thought I’d look into the cultural and natural history of the porcupine and see what interesting tidbits I could come up with to expand the average person’s knowledge of this denizen of our Adirondack forestlands. What I found was really quite interesting.

Sure, we could talk about the size of this mostly nocturnal animal (10-20 lbs), what it eats (herbivore), and where it lives (the woods), but that’s all pretty boring information – dry facts. How about something more interesting, like just how porcupines defend themselves?

Even today it seems that the majority of people still believe that a porcupine can throw its quills. While I can throw a porcupine’s quills, it is simply untrue that the porcupine can. It has no thumbs…how would it be able to pick them up? But seriously, a porcupine’s quills (which are essentially modified hairs) are well-lodged in its own skin and are held in place by connective tissues. The biology and physiology of these tissues are pretty amazing, as demonstrated by Dr. Uldis Roze of Queens College.

Dr. Roze pondered on just how much force it took to pull porcupine quills from a glove of his (courtesy of a porcupine he was trying to capture). Then he wondered how much force it took to pull quills from a porcupine. In the end, his research revealed that in order for a porcupine to release its quills, the animal must first feel it is being threatened. If the animal’s quills are merely pushed against something (let’s say for example the porkie rolled over in its sleep and brushed against the side of its tree cavity den), the quills remain in place in the porkie’s hide, the connective tissues flexing and letting the root-end of the quill press into the porkie and then back out. However, if the animal feels its life is at risk, it raises its quills. The normally flexible connective tissues beneath the skin now stiffen up. When the quills make contact with an outside surface (Rover’s snout, for example), they are forced inwards on the porcupine with as much force as they are forced into said snout. As the quills press into the porkie, the now inflexible connective tissues break, allowing the quills to be easily released from the porkie’s skin, pulling loose as Rover backs away in surprise.


But wait! There’s more.

Humans, as we know, are rather deficient when it comes to the world of smell. Our olfactory functions simply do not stack up to those of many of our other travelers on this spaceship we call Earth. Anyone with a dog can verify this. But even humans, with our lowly noses, can distinguish another trait of the porcupine: its warning scent.

It turns out that porkies, like most animals, would prefer to avoid a fight. After all, if you can scare away your enemy before it engages you, your odds of survival greatly increase. So, when a porcupine feels threatened, it raises its quills and turns its back to its would-be adversary. Located at the base of its back is a patch of skin sprouting specialized quills. These quills have more surface area than the regular quills do and one of their functions is to disseminate pungent odor molecules into the surrounding air. This odor is described by Dr. Roze as something like “the smell of a goat or perhaps an exotic cheese.” Apparently it is quite distinctive, and any animal that has no previous experience with porcupines may learn the hard way to associate this odor with pain. I imagine it works as a pretty good deterrent, in a once-burned-twice-shy fashion.

I also discovered, in my research, that porcupine quills tend to fluoresce a bit in the dark. Unfortunately, that was all I could find about this phenomenon – it exists. I’m sure someone somewhere must have studied it, but so far that information is not available on-line. The only thing I found in relation to this is that this fluorescence can make dyed quills (such as those used in many native arts, like the quillwork basket in the photo) a little more brilliant than expected.

I don’t know about you, but my curiosity in the porcupine has definitely been piqued. I have only seen about three live porcupines in my life (four, if you count the one we had at the zoo where I worked). Since roadkilled porkies are more common, I may pull over the next time I see one and take note of its porcupine traits. Will it have the pungent odor? Can I distinguish the specialized odor-dispersing quills? Maybe I can get some good photos of its pebbly-textured heel pads (an adaptation that helps the animal climb trees). Or maybe I’ll simply collect its quills, find some natural dye recipes, and add them to my collection for making quillwork art.


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Ellen Rathbone

Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.

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