Congratulations to Wanda Rice, the first Naturally Curious reader to recognize sign made by a squirrel collecting nesting material. Many people thought it might be a porcupine at work, but porcupines, as “hellomolly” pointed out in her comment, do not leave strips of bark hanging, while squirrels do.
In the Mystery Photo, an Eastern Gray Squirrel had been shredding and collecting the thin bark of a Maple Sugar sapling to line its nest with. Gray squirrels nest throughout the year, but nesting activity peaks during their two mating seasons (December -March, and May – July). They build two types of nests – large, round, leafy nests among tree branches (dreys) and cavity nests, the latter being preferred during the colder months. Abandoned woodpeckers nests as well as natural-formed cavities provide additional protection in the winter from predators as well as the elements. (Drey broods are 40 percent less likely to survive than squirrels born in tree cavities — a hole no wider than three or four inches protects them from large predators such as raccoons.) Both types of nests are lined with soft material such as lichen, moss, grass, pine needles and shredded bark.
The effect of a squirrel’s stripping a tree’s bark depends on the extent of the damage. Usually a young tree is chosen due to the thinness of the bark and the ease with which it can be stripped. Although a tree can survive with some of its bark removed, it will die if the damage is too severe or bark is stripped off around the tree’s circumference. Stripped bark not only provides nesting material but the process of stripping the bark exposes the tree’s cambium layer which contains the nutrients and sugars a tree has produced and which squirrels readily consume. (Eastern Gray Squirrel photos by Margaret Barker Clark)
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