Tree damage from squirrels can be severe during winter months
Although not thought of as a regular part of a squirrel’s diet, the gnawing and stripping of bark from trees can be locally common in winter months. This activity can have severe, if not fatal consequences, for individual trees chosen for this assault.
There are a number of wildlife species who utilize tree bark as a food source. Beavers cut down trees to get to the twigs and limbs. Porcupines have a varied diet, but strip bark from upper branches of trees through winter months when bark, twigs and needles make up most of their diet. Mice, voles and rabbits will gnaw the bark of younger shrubs and trees during winter. Usually mice and vole damage will be under the snow, while rabbit chomping will be above snow level. If this feeding encircles the trunk it prohibits all sap flow and the affected tree will either die or sprout from below the damage.
Many individuals think of squirrel as nut or seed eaters. It varies with species, but squirrels are a more opportunistic feeder imagined. In addition to nuts and seeds, they utilize small fruit, field crops like corn, insects, and mushrooms and are active visitors to bird feeders. Fox and eastern grey squirrels have been found to strip and apparently feed on inner tree bark as well.
(photo) Bark stripping by eastern fox squirrel in sugar maple stand, Houghton County (photo: Kirk Hammel)
In the northern regions, this bark gnawing activity is most evident in the late winter months, but there have been reports of different tree species being affected throughout the seasons. There are several theories as to why squirrels do this, but no hard evidence has been presented as an explanation.
One theory that has merit claims that they eat whatever tree species tastes good or satisfies a mineral craving caused by a dietary deficiency. As squirrels seem to prefer smaller, younger trees that support their weight, or the thinner barked upper branches of older trees, it is surmised they are simply stripping the thinner outer bark to get to and feed on the nourishing inner bark.
Stopping the squirrels isn’t a practical option in a forest setting, thus they will be persistent in this activity. If the inner bark is removed all the way around a branch, that branch will die. If the inner bark is removed all the way around the main stem of the tree the whole tree is most likely lost. A landowner may be able to protect an open-grown tree with no buildings or wires close enough for the squirrels to jump over onto the tree by ringing the trunk with a metal barrier they can’t climb over.
Michigan State University Extension offers a pest management page for assistance is identifying plant pest issues. Although identification and suggestions for remedy of some pest issues are offered; the feeding of squirrels on tree bark is simply part of nature and may well be something landowners are just going to have to adjust to and learn to tolerate.
Please feel free to contact Mike Schira via email if you have or know of any research-based insight into the bark stripping habits of our native squirrel population.