Why Squirrels Are A Sapling's Biggest Enemy (And How To Stop Them)

A squirrel's diet typically consists of nuts, berries, seeds, plant shoots, and garden vegetables. They eat the new growth on the tips of trees and branches, as well as the bark, and when their traditional food sources aren't available, they feed on insects, young birds, and even eggs. Squirrels chewing new growth on trees is rarely fatal, and most trees can tolerate some bark stripping if it's not much more than a quarter of the way around. The tree is at risk when squirrels chew the bark on a branch or the trunk all the way around, girdling it and exposing the underlying tissue. When this happens, the sap stops flowing, which can be fatal to saplings.

Making sure your trees are healthy provides them with defenses against damage caused by gnawing squirrels and other conditions that may be attacking your tree's bark. There are a lot of theories, but little scholarly research about why squirrels do this. Since it frequently happens in winter, the squirrels could be looking for food or hydration from the sap. One study suggested that the rodents are in search of calcium. A squirrel's teeth grow continuously, so one theory is that they gnaw bark to grind them down. Some believe squirrels may gnaw simply out of restlessness or stress. Overall, the consensus seems to be that it's just something squirrels do. 

You can distinguish squirrel damage by the piles of twigs on the ground under the canopy. Vole, mouse, and rabbit damage will look different. The twigs will be about eight inches long with a handful of leaves attached, and the cuts will be at an angle if they're the work of squirrels. Rabbits chew around the base of the tree because they can't reach the branches. Vole and mouse damage will be below the snow level in winter. Since mature trees rarely succumb to the damage left by squirrels, you probably won't need to take any action unless it's extensive. However, if the damage has gone too far, it may be too late to save the tree. Saplings are far more vulnerable, even to minor damage.

As anyone who has battled squirrels at the bird feeder can attest, physical barriers are the most effective way to combat the rodents. This can include tightly-woven wire fencing placed far enough away from the sapling's trunk to keep squirrels from reaching it. Keep in mind that if the animal can jump from the top of the fence to the tree, the fence is useless. Metal sheeting wrapped around the trunk and branches is another option. Neither method is aesthetically pleasing, but they will protect the sapling until it reaches a stage where the damage is survivable. Other options include installing motion-detecting sprinklers that come on when a squirrel is near or trapping the animals and moving them out of range of the sapling. Typically, a squirrel's home range usually spans between 1 and 100 acres.