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Porcupine Feeding Technique

12-18-13  porcupine incisor marks IMG_0150In the winter, the bulk of a porcupine’s diet is the inner bark, or cambium, of trees. The porcupine removes the outer bark (unless the tree is young or has thin outer bark and then it eats the outer bark as well) in order to reach the cambium layer, which lies directly beneath the outer bark. At this point the exposed surface is very smooth, more finely finished than the work of a beaver. Then the porcupine removes the cambium in small, triangular patches, each patch composed of five or six scrapes converging at one point, like sticks in a tepee. The point where the scrapes meet is where the upper incisors are placed and held fixed against the tree. The lower incisors scrape, making a fresh path with each scrape, as the lower jaw swivels in a narrow arc.

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16 responses

  1. Does this creature contribute to the nature of things in any way? Besides porcupoo?
    They are interesting, but …

    December 19, 2013 at 1:48 pm

    • Hi Marilyn,
      I guess when I think about an animal, I don’t usually ask what it contributes to the ecosystem; rather, I marvel at the adaptations (ever-growing incisors, modified hairs (quills), pebbly-soles on its feet for climbing, etc.) that it has. As far as contributions, if you’ve ever examined an old pile of porcupine scat, you know that many fungi thrive in it. Insects gather at fresh cuttings to drink the tree sap. Certainly their quills were used as a medium of exchange for Native Americans. Porcupines provide fishers with food (though you may not be a fan of fishers, either!). I can almost promise you that if you read Uldis Roze’s The North American Porcupine you will come away with a new admiration for this species!

      December 19, 2013 at 3:27 pm

      • Thank you!

        December 19, 2013 at 8:35 pm

      • I read the first pages of Roze’s book on Amazon – and I am about to order a copy. My attitude toward these critters came from being kept awake nights from their gnawing in the lumber pile under our camp, and the mess from their living there for ages. Otherwise I find them endearing – and now fascinating. Thank you for suggesting this book.

        December 20, 2013 at 1:52 am

      • So glad you are getting the book — it’s fantastic! Also glad you find them endearing, as I do!

        December 20, 2013 at 2:28 am

  2. Ann

    Can the tree survive this? Thanks for all the fascinating information.

    December 19, 2013 at 2:00 pm

    • As long as the porcupine doesn’t girdle (eat a ring around the entire tree, which would cut off transportation of water and nutrients) the tree, it can survive, Ann!

      December 19, 2013 at 3:17 pm

  3. And, don’t forget, a girdled tree which dies becomes a ‘snag’ and that means a lovely apartment building for all sorts of creatures–flying squirrels, nuthatches, owls. Woodpeckers and other birds love to eat the insects still residing within, and, if nothing else, a dead tree makes room for more living trees. It’s the continuity of life!

    December 19, 2013 at 4:10 pm

    • I couldn’t agree with you more, Helen. Well put! (Just put your calendar in the mail.)

      December 19, 2013 at 5:07 pm

  4. Kathie Fiveash

    I’ve seen porcupines in the winter in hemlock trees eating the branch ends. Is that a secondary food?

    December 19, 2013 at 8:37 pm

    • Hi Kathie,
      Yes, porcupines LOVE the tiny buds at the tips of hemlock branches. They go out as far as they can on the slender branches, pull the end of the branch in and nip off the tip. Then they eat the buds and drop the branch tips on the ground beneath them. I always am keeping an eye out for a hemlock with scattered hemlock “nip twigs” on the ground — a sure sign of recent porcupine activity!

      December 19, 2013 at 9:09 pm

  5. Penny March

    Do the upper and lower incisors grow at different rates? It would seem that the lower are getting more of a workout than the upper in this case.

    December 19, 2013 at 10:16 pm

    • Hi Penny,
      Good question! To my knowledge, they grow at the same rate, but I am not positive about that. They also wear against each other (top and bottom incisors) which helps keep them all filed down.

      December 20, 2013 at 2:29 am

  6. Phyllis Sise

    Do you have a mailing address for donations. I am old fashioned.

    December 20, 2013 at 1:33 am

  7. I’ve seen these scrapings and wondered what did them. The ledge ridges around us have many porcupine dens and when I see then down in the yard, usually looking for fallen apples, I tell them to move on before the dog takes an interest in them. Equals expensive vet bills and one unhappy pet!

    December 20, 2013 at 2:10 am

    • You’re right about expensive vet bills — I know all too well!

      December 20, 2013 at 2:28 am

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