In years when food is scarce for squirrels (such as last year when the maple trees did not produce many seeds due to a late frost), they can resort to eating bark to meet their nutritional needs. If this is happening, we recommend offering an alternative food and water source, such as nuts and seeds, to deter them from stripping the bark. Stripping bark can expose the xylem of the tree, leaving it susceptible to insects and diseases. They can also potentially girdle a tree and cause long term damage.
Research indicates that bark stripping has a higher occurrence following a "mast year" where trees produce a bumper crop of fruits and seeds, which may correlate with a higher population of juvenile squirrels. Here is an excellent article from Ohio State University about bark stripping.
EATING TREE BUDS
tree trimming to protect young squirrels
Amy Grewe, Certified Arborist & Co-Owner