Hemlock for lunch

Hemlock for Lunch, from the Undiscovery Channel.

Think of the North American porcupine (Erethizon dorsatum) as a really fat, irritable, slow-moving squirrel. (The irritable part isn’t absolutely certain, but that’s the gist of the genus name, Erithizon.) Like squirrels, porcupines are rodents at home in the trees, with an affinity also for subterranean excavations. But while tree squirrels have evolved to eat and hoard nuts, porcupines are attuned to the leaves, twigs, and bark of trees. On our mountain, they seem fondest of conifers (hemlock, white pine, and Norway spruce), chestnut oaks, elms, and fruit trees, roughly in that order, but we’ve seen them in other trees as well. In warmer months, they may graze on herbaceous plants — there’s little that’s consistent about porcupines. Though generally nocturnal, you can find them out in the middle of a sunny day, too. I suspect they don’t always sleep too well. I hear them moving around under the floor at all hours.

For creatures that spend so much of their time in trees, porcupines have remarkably poor vision, relying instead primarily on their sense of smell and hearing. They certainly don’t look like they belong in the trees, especially when they climb out on a thin branch that bends under their weight. Watching this one today made me think of a trained bear on a unicycle — it just didn’t look natural. But their claws and the rough soles of their feet, together with their tails, seem more than adequate to any arboreal challenge.

I’ve often half-jokingly referred to them as my totem animal, but I don’t think I’m quite as strange as a porcupine — at least, not yet. Porcupines are legendary for their taste for salt, and have been known to eat tool handles, boots, snowshoes, or automobile tires encrusted with road salt. They also sometimes take a shine to radiator hoses and brake linings, and the glues in plywood are like porcupine crack.

Porcupines are fond of the dark insides of things, be they hollow trees, logs, or rock shelters, and will on occasion share sufficiently large shelters with other porcupines, each keeping a studious distance from the others. Though they’re quiet much of the time, they can make a lot of different noises when irritated or aroused. Mating season — late summer and early fall — brings out their full repertoire of coughs, grunts, whines, wails, and moans. Love-struck male porcupines are also said to perform elaborate dances, culminating in a spray of urine over the head of the female.

That may sound a little bizarre, but let’s face it: we’re talking about creatures who are fiercely solitary for most of their existence, and who spend way more time communing with the wind in the treetops than with others of their own kind. Oh, and there’s the matter of the 30,000 hollow barbed quills covering their bodies. That should be enough to make almost anyone a little strange, one would think.

Believe it or not, though, a coat of easily removable quills is a practical enough defensive strategy to have evolved twice. New World and Old World porcupines, like New World and Old World vultures, are not closely related, and resemble each other because of convergent evolution. It would be nice to say that similar ecological niches summoned them into existence — which was the case with vultures — but in fact it is only the New World porcupines that have a close affinity with trees. Many South American species actually have prehensile tails.

Porcupines have two main enemies here in Pennsylvania: people, and the large weasels known as fishers, which are quick enough to dart in, flip them over, and attack their unprotected bellies before they can react. We’ve found a number of dead porcupines around the mountain since the return of the formerly extirpated, reintroduced fishers some five years ago, though it’s possible that bobcats have also killed a few. Fishers are just as solitary as porcupines, and have huge territories, so the death of a fisher two weeks ago on a small road a half-mile from the base of the mountain was probably very good news for our porcupine population — and bad news for the trees that, for whatever reason, have the misfortune of attracting porcupines year after year.

The poor eastern hemlock (Tsuga canadensis) in the above video is one such tree. It’s one of the few hemlocks in the upper half of the hollow, and as such gets more than its fair share of attention from the conifer-loving porcupines. It’s undergone such radical pruning over the last couple of decades, I’m amazed it’s still alive, but hemlocks can take a long time to decide to cash in their chips. They’re not, however, the sort of tree to sprout a bunch of new branches in response to pruning, so this particular tree has simply become more and more skeletal, with vestigial tufts of needle-bearing twigs at the ends of most of its branches. Judging from the appetite of the porcupine I watched feasting on it today, this winter might well be its last. Porcupines can consume up to a pound of cellulose a day. This is said, by the way, to make them smell like old sawdust, though I admit I’ve never gotten quite close enough to one of them to see if that’s true.

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Don’t forget to submit tree-related posts to the February 1 edition of the Festival of the Trees by January 30. Here’s the call for submissions. Ash laments that he has yet to receive any bark rubbings.

19 Comments


  1. Impressive! I was particularly surprised to see him sever the thinner branch and eat it “out of hand”, all while hanging on to another, none-too-thick branch. Did he finish the branch he cut off, or are they prone to leaving half-eaten branches lying around?

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  2. Yeah, that surprised me a little, too. You can see him/her sizing it up and deciding the best place to sever it. I’ll have to go back and see if s/he ate it all, and post an update. They are messy eaters.

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  3. I LOVE this porcupine!!!!
    his roly-polyness
    is quite similar to the here housed Hap
    who expands daily
    (as he, I think, waits
    for warmer weather to exercise)

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  4. No longer the hyper, wall-climbing kitten, eh? How cool do you keep your house? Maybe he’s just bulking up for warmth.

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  5. I worked at the Philadelphia zoo for a while, and the South American porcupines were one of my very favorite animals to work with… five feet long with those prehensile tails, and big squishy noses. We had special shoulder-length gloves to handle them with. We also had some tenrecs, which are another example of spiny evolution.

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  6. Is it just me or does the pace at which you are chasing the porcupine seem faster than the pace that sled was going downhill? (grin)

    Thanks for both the great sledding experience, and the experience which none of us would ever have seen had it not been for your camera capturing the spiky one. Now, I expect if we could understand Porcupine talk that the lil’ feller is saying “..a drowsy numbness pains my sense, as though of hemlock I had drunk.”

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  7. the house is kept around 50 F.
    except for this room , B.’s study, and the bedroom
    where space heaters rule
    and where HAp usually hangs out
    though he does still go out
    and freqently spends the night out
    but you’re right
    the wall climbing days are behind him
    which is not to say he doesn’t demonstrate
    that he has plenty of Asian leopard in him

    (decapitating a good sized (at least 1.5 lbs)bunny
    eating the head
    skull and all
    in about 30 seconds)
    and then the remainder of the bunny body
    including offal and fur
    in a matter of, at max,
    2 minutes

    I’m just sayin’. . .
    you know
    a predator
    with some of the wild still in him

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  8. “Love-struck male porcupines are also said to perform elaborate dances, culminating in a spray of urine over the head of the female.”

    This is precisely how my husband courted me.

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  9. Kat – Five feet long? Damn. I didn’t realize they got that big.

    Joan – Good catch. I filmed the whole five-minute chase thinking it would make amusing video, but in the end I cut it down to the last minute and doubled the speed. So no, I wasn’t really moving that fast.

    susanne – He still sounds way more energetic than me! I’m glad I let you take him – he’d have worn me out by now (and probably gotten a faceful of porcupine quills).

    David – I think she was just being funny. But yeah, the Tsuga kind of hemlock is not only not poisonous but high in vitamins, I’m heard. Like spruce and pine.

    Dana – Do tell.

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  10. Wonderful, absorbing and amazing. This creature is loveable in an almost Disneyish way, with its slow soft awkward wobbly but determined progress up the tree. I expect it to start singing What A Wonderful World in a Louis Armstrong voice.

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  11. Hi Peter and Natalie – Glad you liked it.

    David – I forgot to say that I went and checked, and found the branch on the ground with roughly 3/4 of the needles consumed.

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  12. My teenage daughter and I just watched and read this together. She was fascinated by the porcupine’s talent for climbing trees. The first time I saw it, I thought the porcupine might fall as it advanced to its lunch, but when it released its front feet in order to eat, it really was like a bear on a unicycle . . . on a high wire.

    We stopped at almost every biological term so she could explain them to her poor father. She is very jealous of your woods and weather. I think she may end up living as close as she can to nature.

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  13. Dave___

    not a day goes by
    that I don’t thank you
    for posting his photo up
    I have had over 100 cats in my lifetime
    so far
    and he is
    far and away
    the finest most spectacular
    fascinating cat
    by whom I have ever been possessed

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  14. Thanks for checking back… it’s striking how the details of an animal’s feeding habits can make so much difference to it’s ecological imprint. Some creature, perhaps smaller, that just nibbled needles off the branches in situ might well let the hemlock recover. This guy is more effective (even more human-like) in harvesting his food, and can take branches he couldn’t reach otherwise — but that’s to the detriment of the tree. I guess the leftover needles will eventually join the local mulch, anyway.

    Come to think of it, how does your land stand in terms of the long-term “soil wars”, that is, conifer needle-bed vs. earthworm mulch?

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  15. suzanne – Really? I am so glad he found a good home with you, then. Best blog post I ever wrote. (And now I’m kicking myself that i didn’t put that in the roundup of “20 Things About Via Negativa” for my fifth blog-day last month.)

    David – Well, it’s really only a matter of time before the woolly adelgid destroys all the hemlocks on the mountain – we have it in the hollow now, so very likely the next ten years are going to be agonizing ones. (The lower half of the hollow, not shown in that sledding video, contains several hundred hemlocks.) Given that, I don’t begrudge the porcupines a tree or two.

    Since this was an orchard from the 1850s on, our soils are quite overrun (overcrawled?) with invasive earthworms. Which may have a lot to do with why so many acres of woods are being taken over by Eurasian shrubs, grasses and forbs.

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  16. Oh, and for the last line of your original, they clearly smell like… YEOWW! :-)

    Reply

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