Squirrel tooth marks are small and look like narrow scratches where the animals have removed the tree’s bark. / Photo Credit: Linda Williams, Wisconsin DNR
By Linda Williams, Forest Health Specialist
Linda.Williams@wisconsin.gov or 920-360-0665
If something chewed the bark off your tree, how would you go about determining the culprit?
Quite a few animals can damage bark on trees, from deer and bears to rabbits and mice. But the damage from squirrels and porcupines can look very similar, especially from a distance. So, how can you tell the difference?
Porcupine teeth are larger than squirrel teeth, and they leave larger scrape marks as they remove tree bark. / Photo Credit: Linda Williams, Wisconsin DNR
In northern Wisconsin, porcupines will often feed on conifers such as spruce and red pine, although they can also feed on many hardwood species. Porcupines can strip large areas of bark off the tree and will scrape the tender and tasty cambium and inner bark from the tree. When feeding on trees with thicker bark, large pieces of bark will be dropped to the ground below the tree.
Gray squirrels will do similar damage in late winter as they remove tree bark. They prefer maples, which have a sweeter cambium and inner bark than some other tree species. Squirrels will also remove bark and drop it to the ground, but the pieces of bark will be smaller — usually the size of a nickel or quarter.
Both porcupines and gray squirrels can be found feeding in the tops of trees, although damage can sometimes extend all the way to the ground.
Look closely at the teeth marks on damaged areas of the tree. Porcupine teeth are larger and will leave scrape marks that are about 1/8-inch wide, while squirrel teeth are much smaller and leave tiny grooves only about 1/16-inch wide.
Porcupines remove large chunks of bark and drop them to the ground as they feed, as shown on this red pine tree. / Photo Credit: Linda Williams, Wisconsin DNR
If you’re noticing unacceptable levels of damage, there are a number of online sites that can provide ideas for control or prevention of squirrel or porcupine damage. Or, you can reach out to your local wildlife biologist for ideas.