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Porcupines Staying Warm Inside & Outside of Dens

If you’ve ever set eyes on a porcupine den, be it in a hollow tree or rocky ledge, you know that protection from the elements, especially cold temperatures, appears limited. While there is slightly better thermal protection in a rock den as opposed to a hollow tree, neither has any insulation, other than the ever-accumulating bed of scat on the floor of the den, and the entrance is wide open. Even so, porcupines save an average of 16% of their metabolic energy by occupying their dens instead of open terrain, due primarily to the shelter from wind that it provides. In addition, porcupines have two layers of fur which insulate them so efficiently that the outside of their bodies are approximately the same temperature as their surroundings, minimizing heat loss.

Porcupines do venture out of their dens and spend between seven and twelve hours a day outside, without the protection of wooden or rock walls. How can they survive this environment? When outside the den (usually when feeding at night), they are often in conifer stands, and a coniferous habitat provides the same energy savings as a den. Eastern hemlock, which is a preferred winter food, has needles layered so thickly that porcupines don’t lose a great deal of heat to the open sky. The trunks and foliage of hemlocks also re-radiate at night some of the energy they absorb in the day.

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3 responses

  1. Sounds like near perfect adaptation. I feel concern about the decline of eastern hemlock due to wooly adelgid and its impact on the many species that depend on them. Any thoughts?

    January 21, 2016 at 3:42 pm

    • Hi Eliza,
      I think your worries are warranted. Cold weather is a deterrent to its presence in northern states but with global warming, we could well see an invasion in the not too distant future, and that spells disaster for porcupines, among other living things.

      January 23, 2016 at 11:20 am

      • We already are seeing vast stands turning brown and dying back. Sad, sad!

        January 23, 2016 at 10:32 pm

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