Issue 6, May 29, 2009


We have received a number of calls concerning damage by squirrels to trees. Damage primarily consists of the bark being stripped off of one to three inch diameter branches for one to several feet. Typically, the bark is removed from the entire circumference of the branch, girdling it. At the edge of the removed area, one can detect arcs that are about one-quarter inch wide cut through the bark to the sapwood. These correspond to the size and shape of the squirrel's front teeth. The girdled branch dies. Damage typically occurs during the winter, but can occur at any time of year. Typically, hardwood trees are attacked with maples appearing to be the most common.

Twig clipping is commonly caused by squirrels at this time of year. Twigs that are one or more feet long and about one-quarter inch in diameter are bitten through and fall to the ground. Caused by rodents with large front teeth, clipped twigs will have a clean, angled cut, similar to that made by a hand pruner. After several days, the ground may be littered with a hundred or more twigs. This usually causes little damage to the large trees that are typically attacked.

Typically, gray squirrels are the culprits, although this same damage can be caused by fox squirrels or pine (red) squirrels. Gray squirrels are usually gray or black, although white squirrels, albinos, are common in Olney, IL and are occasionally seen elsewhere. Squirrels build twig and leaf nests on tree branches and also nest in branch forks and trunk cavities. Each squirrel will have a home range of about one acre. Squirrels feed on nuts, seeds, buds, leaves, bulbs, bark, insects, and fruit.

Although bark and twigs are food for squirrels and some damage will occur if squirrels are present, large amounts of damage are usually caused by one individual. Squirrels are also creatures of habit, causing damage to only one or a couple of trees when many similar trees are nearby. For this reason, removing the individual squirrel or restricting access to only one or a few trees is likely to be successful.

Squirrels can be live-trapped using nutmeats, sunflower seeds, fresh orange slices, sweet corn, or oatmeal for bait. Because squirrels are protected game animals, consult the Illinois Department of Natural Resources for the necessary permits before removing squirrels. Although trapped squirrels can be released at least 5 miles away, humanely killing the squirrel is usually recommended. A high percentage of relocated mammals die, and they disrupt the home ranges and ecology of the residents of the same species in the area where they are released.

Squirrels can be excluded from a tree by attaching a two-foot wide band of sheet metal around the trunk at least six feet off the ground. Attach the metal with encircling wires held together with springs to allow tree growth. This is only effective if there are no nearby trees or buildings to jump from and reach the tree. Repellents such as Ropel, thiram, or capsaicin can be applied to the bark to provide protection.--Phil Nixon

Phil Nixon

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