Every once in a while, tree squirrels enter structures and cause damage. Common pest species include the gray squirrel (Sciurus carolinensis), the red squirrel (Tamiasciurus hudsonicus), the flying squirrel (Glaucomys spp.), and the fox squirrel (S. niger). They can be differentiated from ground squirrels, such as the 13-lined (Ictidomys tridecemilineatus) and the California (Otospermophilus beecheyi) species, because the latter group lives underground and have shorter, less bushy tails.
As their common name implies, tree squirrels tend to inhabit wooded areas and build their nests in trees, but as people expand their settlements into these areas, the squirrels frequently establish themselves in attics and garages to store food and find shelter. Around buildings, they often gnaw on the exterior and interior walls and timbers, on cables and electric wiring, and on any items that may be in storage. They may also:
- Be noisy in their activities.
- Bite if cornered.
- Cause ectoparasite problems to occur in nesting areas.
- Damage trees, gardens and ornamental plants.
- Short out electric power transformers during their activities around power lines.
Most tree squirrel species have two litters of young per year, in early spring and late summer. Some flying squirrels may produce only one litter per year. The number of young varies between three and eight squirrels, depending on the species.
Tree squirrels are most active in early morning and late afternoon. They feed on nuts, seeds, buds, leaves, bulbs, bark, insects and fruit. They frequently store their food in outdoor caches.
Most squirrels are protected game animals, so consult with local game conservation offices to obtain any necessary permits. Avoid violating any fish and game laws during control programs.
The first step in managing tree squirrels is to determine how they are entering the structure, and then make every effort to exclude them. Pay attention to utility lines, drainpipes, uncapped chimneys, ivy and other ornamental plants that cling to the house, and attic or basement vents and windows in disrepair. They will sometimes gnaw straight through the exterior of buildings, such as cedar-shingled homes, to gain entry. Seal all existing openings with sheet metal or 0.5-inch hardware cloth.
Prune all overhanging tree limbs back at least 10 feet. Squirrels can be kept from climbing trees by placing a 2-foot-wide metal band around the tree trunk, 3 to 4 feet above the ground, although this may not be aesthetically acceptable in many cases.
When screening, repelling and removing tree limbs do not solve the problem, trapping may be necessary.
Truman’s Scientific Guide to Pest Management Operations, Seventh Edition, available for purchase at MyPMP.net/shop