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Scientific Name: Fox Squirrel Sciurus niger

Photos by Erin Bauer of Univ. of Nebraska Lincoln

Damage to Tree Bark

Fox squirrel (Sciurus niger) and gray squirrels' (Sciurus carolinensis) damage to tree bark (called bark stripping) can be quite severe. See photo at right by Dallas Virchow.

We have recently heard from a gentleman in Pennsylvania that red squirrels (Tamiasciurus hudsonicus) also strip bark. We would love to hear from anyone who has had similar experience.

Identification of Bark Stripping

• Fox squirrels exist in the middle portion of the continental U.S.
• Gray squirrels exist in the Eastern portion of the continental U.S.
• Typically, strippings are 1/2 inch wide and three to six inches long. Other small limbs branches of one- to two-feet in length and 1/4 to 1/2 inch diameter are clipped and dropped to the ground.
• Squirrels prefer to strip branches that are horizontal, but have been known to strip trunks too. The damage can be extensive.
• Bark stripping usually occurs in late winter. But it can occur in the spring if trees don't produce mast.
• Incisor Widths--These figures encompass the range in the width of teeth between upper and lower incisors and between male and female squirrels.
  • Gray squirrel (Eastern)--1.17 to 1.74mm
  • Gray squirrel (Western)--1.19 to 2.25mm
  • Fox Squirrel (Eastern)-- 1.40 to 2.30mm

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Types of Trees Stripped

• Ash (Boise, ID)
• Atlas Cedar (ID)
• Autumn Olives (NE)
• Corkscrew Willow (OR) December, 2008
• Elm (San Mateo, CA) May, 2009 Damaged branched up to 2-inches in diameter
• Ginkos (TX)
• Globe Willow (ID)
• Hackberry (NE)
• Honeysuckle (NH) (Gray Squirrel) Winter 2008/9
• Honey Locust (NE)
• Japenese Maple (OR) December, 2008
• Linden--Small Leaf (Ontario, Canada) stripped in Mid-November, 2008.
• Maple (FL, MN, NE July, 09; )
• Maple, Japanese (TX)
• Maple, Red (NE)
• Maple, Sugar (MN)
• Oaks--various varieties (TX)
  • Pin Oak
  • Live Oak (DFW Airport, TX, June, 2009)
• Pecan (GA June, 2009)
• Poplar (GA)
• Poplar (Tulip Variety)
• Russian Olive (Milton, Ontario)
• Sycamore (NE)

Why Squirrels Strip Bark

There are essentially three theories.

1. Pregnant females often don't eat just prior to giving birth. Bark stripping may be their way of responding to the pain.
2. Searching for water (although this theory has been weakened by observing that squirrels strip bark even when during a wet spring, stripping during a dry August reaffirms this theory).
3. Searching for food by eating the inner bark layer.

Squirrels also damage trees by limb/twig cuttings

• Timing: Typically occurs in Spring (nest construction) and Fall as in (crop gathering). Pin oaks seem to be typically hard hit (Source: Jerry Pickel of PA).
• Tassel-eared squirrels use the twigs to feed on the nutrients found in the cambium and subcambium layers of pine and firs (Source: Richard Wadleigh).

Click to learn How To>> Stop Squirrel Bark Stripping