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Porcupine Digestion

1-18-17-porc-img_3485Porcupines are herbivores, and as such, possess micro-organisms which digest the cellulose in the food that porcupines consume. These microflora, primarily bacteria, are located in a pouch called the caecum, located at the beginning of the large intestine. One of the most essential nutrients for porcupines is nitrogen, and their winter diet of bark does not provide enough to sustain them. Thus, most porcupines depend on reserves they build up in the summer and fall, and in so doing, lose weight during the winter.

One might wonder why porcupines don’t simply increase the amount of bark that they eat in order to get the required amount of nitrogen. The reason is that the process of bacterial digestion of cellulose is relatively slow – it takes two days for food to pass through the porcupine’s digestive system. If it were to pass through any quicker than this the bacteria would not have enough time to properly digest the bark. (Source: The North American Porcupine, by Uldis Roze)

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7 responses

  1. Laura

    Fascinating! I have always loved these animals and love learning more about them.

    January 18, 2017 at 7:45 am

  2. Arlene

    A couple of years ago, porcupines were eating the cedar shingles on my house. This was despite the fact that I live in the woods surrounded by a variety of native trees!

    January 18, 2017 at 7:46 am

  3. Postans, Maryann

    Hi Mary-

    As far I know, nitrogen is not stored in an organism like fat is. Your body takes in nitrogen and makes proteins (ex. muscle) and DNA but it can’t take it in to store it like glycogen (carbohydrate) or fat (triglycerides). Protein is a terrible energy food, but it sounds like your article is saying it is stored as energy. There is also something in the recesses of my memory about how the liver breaks down any excess amino acids (building blocks of proteins) that carry the nitrogen. I am in the middle of exams otherwise I would research it all for you.

    I will research more when I have time.


    On Wed, Jan 18, 2017 at 7:27 AM, Naturally Curious with Mary Holland wrote:

    > Mary Holland posted: “Porcupines are herbivores, and as such, possess > micro-organisms which digest the cellulose in the food that porcupines > consume. These microflora, primarily bacteria, are located in a pouch > called the caecum, located at the beginning of the large intestine” >

    January 18, 2017 at 8:03 am

    • Thank you, Maryann! Perhaps I misunderstood Roze’s assertion. According to him porcupines can’t sustain their weight in winter due to the lower level of nitrogren in tree bark compared to their summer diet. He stated that they survive because of their summer/fall “reserves”, but perhaps (?) he wasn’t saying it was necessarily the nitrogen in the reserves that kept them alive…

      January 18, 2017 at 8:33 am

      • Elizabeth

        Mary, I’d recommend getting in touch with Uldis Roze himself if you want answers. Some years back I had a question about albino porcupines and had a lovely little email correspondence with him. Very nice fellow, and quite helpful. I don’t have contact info., but found him before by looking online. (I see he has a Facebook page.)

        January 18, 2017 at 10:34 am

      • Just emailed him! Thank you!

        January 18, 2017 at 1:05 pm

  4. Kathie Fiveash

    So interesting how different herbivorous animals manage the cellulose problem. Big ruminants multiple stomachs to handle the digestion of cellulose. Their size makes it possible for them to carry that extra weight of organs and still be able to flee big predators. Snowshoe hares (and I think other rabbits too) are small prey animals, and have to be able to run fast from predators. They can’t carry around extra weight, and they handle cellulose by passing their waste through the system twice. The first time through, the poop comes out dark and wet and jellyish, and still has a lot of the nutrients in it. They eat that first poop right away – I think they may pass it mostly next to their scrapes – and redigest it. The second time through it comes out as the dry, grassy-looking little pellets we think of as rabbit poop. It sounds like porcupines basically pass the cellulose through their guts very slowly. Having a different predator avoidance strategy – their quills – they don’t have to worry about the extra weight, and can move more slowly through the forest. I wonder what other strategies are out there!

    January 18, 2017 at 9:54 am

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