Seeing bark stripped from trees? How to tell if it was caused by a porcupine

Tree with porcupine damage
Tree with bark stripped away by a porcupine. Photo: DNR

Have you seen trees with large areas of their trunks stripped of bark? It could be bear or beaver damage, but what if the removed bark area goes up to nearly the top of the tree, higher than a bear or beaver would go in search of tasty bark or bugs? It’s true that fox squirrels and gray squirrels strip also bark from trees, and so do raccoons, but don’t forget about another forest dweller: the porcupine.

If you see bark striped from a tree, strips hanging from limbs, and perhaps piles of the stripped bark at the base of the tree, you might have seen the work of a hungry porcupine. And you can especially suspect porcupine if there are convenient branch “seats” for the animal to be perched on as it strips the bark, and eats some of the bark and licks and chews at the sugary wood surface beneath.

Porcupine are present in both eastern and western Washington. We don’t see the animals very often – but if you get out into the forest often enough, you will see their damage frequently.

Porcupine commonly climb up trees and strip the bark. They cause wounds and serious injury to the tree if they girdle the tree by removing the bark all the way around the circumference of the trunk. They tend to like fairly thin bark and like to sit on a branch or in a crotch where they can feed leisurely. They eat a variety of plants, including the bark and foliage of conifer trees. It’s particularly easy to strip the bark from conifer trees in the spring when the bark is relatively lose and pliable.

While porcupine can damage healthy trees, the biggest source tree damage in Washington State, especially in young trees, comes from black bears. The Washington Forestry Protection Association estimates that a single foraging black bear can peel bark from as many as 70 young trees a day. Trees between 15 and 25 years — especially Douglas-fir, western hemlock and western red cedar — are  popular targets because of the sweet layer of the trunk that animals can find just under the bark. The damaged trees can die but in doing so also become home to the many species of wildlife that take shelter and build nests in diseased or hollow trees.

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