Tree squirrel damage to trees: stripped bark and clipped twigs, as extension services describe it

This page reports what the official source says. It is not legal advice: ask the office named here. Rules on controlling squirrels differ by place. The University of California note below describes California's Fish and Game Code, administered by the California Department of Fish and Wildlife, and the University of Maryland note says a Maryland Department of Natural Resources permit may be needed to trap squirrels. The page describes what the sources say the damage looks like and the guards they list. It does not say what to do about any tree or animal. For protected species and nests in tree work, see the guide on wildlife and the law.

What the damage looks like

UC IPM (Pest Notes: Tree Squirrels, publication 74122, August 2016) says squirrels have a tendency to strip bark to feed on the juicy inner bark layer, the cambium, which causes injury to trees. It illustrates this with bark chewed off a branch by the eastern fox squirrel, which it calls by far the most serious tree squirrel pest around homes and gardens in California towns and suburbs. The University of Maryland Extension Home and Garden Information Center (Squirrel Damage on Trees and Shrubs, updated February 28, 2023) says that, in their search for food, eastern gray squirrels often destroy the growing tips of young trees and shrubs by stripping bark from trunks and branches, and says squirrels sometimes strip the bark off limbs.

Maryland adds a second, milder mark: squirrels clip branches and small twigs to build their nests, which litter the ground under trees. It says this seldom damages the tree and little control is necessary. Nests of sticks, leaves and shredded bark sit high in trees, and UC IPM says squirrels also nest in tree cavities and in enlarged woodpecker holes.

The University of New Hampshire Extension (Looking for Red Squirrels, November 8, 2022) describes the leavings of red squirrels in conifer forests: a stump or log covered with a pile of cone scales where they have fed, used over and over, called a midden. It says red squirrels feed on seeds of spruce, fir, hemlock and white pine, and hide seeds for winter.

What they eat from trees

Utah State University Extension IPM lists nuts and acorns, seeds, berries, tree bark and fungi as the main diet of tree squirrels. UC IPM lists a wide range of seeds such as pine nuts and acorns, fungi, insects, bird eggs and young birds in their natural habitats, and fruits and nuts in gardens, including almonds, walnuts, oranges, avocados and apples. It says squirrels can strip a tree of its crop in a short time. The University of Maryland Extension fact sheet on tree squirrels (FS 607, updated May 13, 2021) lists acorns, beechnuts, hickory nuts, walnuts, and elm and maple seeds, and says nuisance squirrels periodically damage trees as well as gardens, wires and crops.

Look-alikes

Utah State University Extension Forestry (Utah Forest Facts 038) says squirrels and other small mammals also remove tree bark, but make smaller tooth marks than the grooved marks about 5 mm wide it describes for porcupines. See the page on porcupine damage. Gnawing at the soil line is covered on the page for voles, and rows of small holes in bark on the page for woodpeckers and sapsuckers.

Guards and rules the sources list

UC IPM says it is virtually impossible to keep squirrels out of fruit or nut trees because of their climbing and jumping, though netting a single tree may protect its crop if other food is easily available, since squirrels can gnaw through plastic netting. Utah State lists a metal collar around the trunk to keep squirrels from climbing.

On the rules, UC IPM says tree squirrels are classified as game mammals by the California Fish and Game Code and can be controlled only as provided by the hunting regulations, with two exceptions. Eastern fox squirrels found injuring growing crops or other property may be controlled by the owner or tenant without a permit. For gray squirrels, an owner or tenant whose property is being damaged may apply to the California Department of Fish and Wildlife for a revocable permit. It says it is not legal to use poison baits to kill any tree squirrel species, and that releasing a tree squirrel elsewhere is illegal without a permit. Maryland describes relocating trapped squirrels with the landowner's consent, and says a Department of Natural Resources permit may also be needed to trap them.

The other animals in this group are listed on the wildlife damage to trees page.