Figure 1 Eastern Gray Squirrel.
- Identify common squirrels in the northeast.
- Understand squirrel biology and characteristics important for resolving conflicts.
- Demonstrate the ability to educate clients about management options for squirrels.
- Identify various risks involved with squirrels in and around homes.
Squirrels cause economic losses to homeowners, and are a nuisance to people with birdfeeders. Squirrels chew on soffits, eaves, and electrical wires. They may nest in attics or chimneys. People who feed birds often lose seed, and feeders are damaged by squirrels.
Fox and gray squirrels are usually classified as game animals. Flying squirrels are often fully protected as non-game wildlife. Red squirrels may be unprotected in some states. Check with your state wildlife agency to determine the legal status of squirrels in your area.
In this chapter, tree squirrels are divided into 3 groups:
- large tree squirrels, including the eastern gray squirrel (Sciurus carolinensis) and fox squirrel (Sciurus niger);
- small tree squirrels, including the red squirrel (Tamiasciurus hudsonicus); and
- flying squirrels, including the southern flying squirrel (Glaucomys volans) and northern flying squirrel (Glaucomys sabrinus).
Eastern gray squirrels (Figure 1) typically are gray, but have some variation in color. Black individuals are common in northern parts of their range. Local populations of white gray squirrels are found in upstate New York and other localities. White gray squirrels are not albino. They have gray on the back of their heads, necks, or shoulders. Fox squirrels typically are orange-brown, but color varies greatly from all black to silver gray.
Red squirrels are red-brown above with white under parts. They have small ear tufts and often have a black stripe separating the dark upper color from the light belly.
The most distinctive characteristics of flying squirrels are the broad webs of skin connecting the fore and hind legs at the wrists, large black eyes, and the distinctly flattened tail. The 2 species of flying squirrels that occur in the northeastern US are very similar in appearance.
Eastern gray squirrels are 16 to 20 inches long and they weigh 1¼ to 1¾ pounds. Red squirrels are considerably smaller. They are 10 to 15 inches long and weigh ⅓ to ⅔ pounds. Flying squirrels are 8 to 12 inches long.
Eastern gray squirrels are found throughout much of the eastern US and often are abundant in both urban and rural areas. Red squirrels are a more northern species that are found throughout most of the northeastern US. The ranges of the 2 species of flying squirrels overlap in the northeast.
Health and Safety Concerns
Squirrels chew on electrical wires, and that may cause building fires. Squirrels may also nest in chimneys creating a fire hazard. If left long enough, squirrels can weaken rafters due to their gnawing.
Gray and fox squirrels are vulnerable to several parasites and diseases. Ticks, mange, fleas, and internal parasites are common. Squirrel hunters often notice bot fly larvae, called “wolves” or “warbles,” protruding from their skin, especially before frosts. The larvae do not impair the quality of the meat, and are not known to harbor diseases dangerous to humans. The droppings of flying squirrels have been associated with murine typhus.
General Biology, Reproduction, and Behavior
Gray squirrels first breed when they are about a year old. They breed in early January, and a small percentage (maybe 10% of adult females) breeds again in mid-summer. Younger squirrels often breed only once during their first season. The gestation period is 42 to 45 days.
During the breeding season, noisy mating chases take place when 1 or more males pursue a female through the trees. Gray squirrels have about 3 young per litter. At birth they are hairless, blind, and their ears are closed. Young weigh about ½ ounce at birth, and 3 to 4 ounces at 5 weeks. At weaning, they are about half their adult weight. Young begin to explore outside the nest about the time they are weaned at 10 to 12 weeks. Typically, about half of the squirrels in a population die each year. In the wild, squirrels over 4 years old are rare, while individuals may live 10 years in captivity.
Tree squirrels rear young in leaf nests (Figure 2), tree cavities, and may use chimneys, attics, or soffits (Figure 3).
Individual home ranges vary from 1 to 100 acres, depending on the season and availability of food. They often seek fruit- and nut-bearing trees and cornfields in the fall. Tender buds of maple trees are favored in the spring. During fall, squirrels may travel 50 miles or more in search of better habitat. Populations of squirrels fluctuate regularly. When population numbers are high, gray squirrels may experience mass emigrations, traveling in large numbers across the landscape, where many individuals die.
Gray squirrels typically occupy any woodlot with mast-producing hardwoods. They also are common in cities, especially in and around parks. Red squirrels prefer mixed-hardwood and conifer forests. Flying squirrels, being more arboreal (tree-dwelling), are most common in areas with large, mature hardwoods.
It is important to distinguish the different types of food storage used by squirrels. Gray squirrels scatter cache, which means they store individual acorns or other seeds in different areas around their home range. Red squirrels, store food in one place. It is not uncommon to find trash-bag-sized piles of conifer cones stored by red squirrels inside attics or gutters, or in piles at the base of a tree.
Gray squirrels typically feed on mast in fall and early winter. Acorns, hickory nuts, walnuts, and a variety of fruits are favorite fall foods. Nuts often are cached for later use. In late winter and early spring, they prefer tree buds. In summer they eat fruits, berries, fungi, corn, and cultivated fruits when available. Squirrels may chew bark from a variety of trees in early spring.
Flying squirrels have similar diets, except they are the most carnivorous of all tree squirrels. They eat bird eggs and nestlings, insects, and other animal matter when available.
Voice, Sounds, Tracks, and Signs
Squirrels emit a variety of sounds including churrs, barks, and squeals. Churrs express anger, barks act as warnings, and squeals occur when a squirrel is terrorized or in pain.
Tracks of squirrels commonly are often observed in mud, soft soil, and snow (Figure 3).
Figure 4. Tracks of a red squirrel. They are similar in structure to gray and fox squirrels. Image by Dee Ebbeka.
Damage to Landscapes
Squirrels may damage lawns or planting beds by burying or digging up nuts. They chew bark and clip twigs on ornamental trees or shrubs planted in yards (especially maples). Squirrels often take seed at feeders intended for birds.
Squirrels do not pose a threat to pets, but will consume bird eggs and nestlings. Flying squirrels are small enough to enter most birdhouses and are likely to eat nestling birds.
Squirrels occasionally damage trees by chewing and stripping bark from branches and trunks. They also eat conifer cones and nip twigs.
Damage to Crops and Livestock
Squirrels may eat planted seeds, mature fruits, corn, and grains.
Squirrels can severely curtail nut production by eating nuts prematurely and by carrying off mature nuts. In fruit orchards, squirrels may eat blossoms and destroy ripening fruit. Red and gray squirrels chew the bark of various orchard trees.
Squirrels do not pose a threat to livestock.
Damage to Structures
Gray squirrels typically gnaw holes the size of a baseball (Figure 5) in wooden structures. Holes of red squirrels are golf ball-sized, and those of flying squirrels are the size of a quarter.
Figure 5. Hole from a gray squirrel. Photo by Stephen M. Vantassel.
Squirrels often travel on power lines and short out transformers. They gnaw on wires, enter buildings, and build nests in attics. They chew holes through tubing used in maple syrup production. Feces of flying squirrels mixed with urine can cause stains (Figure 6).
Squirrels may enter buildings through uncapped chimneys and cause substantial damage. If a squirrel gets trapped in a seasonal cabin during winter, they may chew window framing and panes trying to escape. Carpets and other fabrics can be chewed and destroyed.
Squirrels may also try to nest on chimney dampers, especially in areas with few mature trees with nesting cavities. This creates a fire hazard when the stove or fireplace is first used in the fall.
Damage Prevention and Control Methods
For landowners experiencing long-standing conflicts with tree squirrels, it is helpful to use a variety of cost-effective methods to control the damage.
Trim limbs and trees 6 to 8 feet away from buildings to prevent squirrels from jumping onto roofs. In yards where squirrels cause problems at bird feeders, modify bird feeders with baffles to prevent foraging by squirrels at the feeder itself. Add a hopper to collect spilled seed and prevent feeding on the ground. Use milo or millet seed, as these small, hard seeds are less attractive to squirrels than sunflowers or corn.
Prevent squirrels from traveling on wires by installing 2-foot sections of lightweight 2- to 3-inch diameter plastic pipe. Slit the pipe lengthwise, spread it open, and place it over the wire. The pipe will rotate on the wire and cause traveling squirrels to tumble. Critter Guard® has created a device to stop squirrels from crossing wires. NEVER install wire guards on or near electrical lines. Only professional electricians and employees of power companies should handle power lines.
Prevent squirrels from climbing isolated trees or utility poles by encircling them with a 2-foot-wide collar of sheet metal 6 feet above the ground (Figure 7). Consult the local power company before installing anything on a power pole. Attach metal bands using encircling wires held together with springs to allow for tree growth.
Figure 7. A tree trunk wrapped with aluminum flashing may prevent squirrels from climbing. Photo by Stephen M. Vantassel.
Close openings to buildings with heavy-gauge, ½-inch wire mesh or aluminum flashing. Wire-mesh fences topped with electrified wires may keep squirrels out of gardens or small orchards.
No frightening devices have been proven effective, although strobe lights in attics have shown some promise.
We do not recommend the use of moth balls (naphthalene) to repel squirrels because the chemical can cause severe distress to people. This is an off-label use, and it is illegal in many states.
Ro-pel® is a taste repellent that can be applied to seeds, bulbs, flowers, trees, shrubs, poles, fences, siding, and outdoor furniture. Effectiveness varies greatly, as rodents typically are not deterred by bitter tastes. Another taste repellent, capsaicin is registered for use on tubing and equipment used to collect maple sap.
Polybutenes are sticky materials that can be applied to buildings, railings, downspouts, and other areas to keep squirrels from climbing. Polybutenes can be messy, and can stain building finishes. A pre-application of masking tape is recommended. These products are best used to stop gnawing damage indoors. They quickly become covered with dust and dirt outdoors and lose effectiveness.
No toxicants are registered for the control of tree squirrels.
Offending squirrels can be controlled using a .22-caliber rifle, or shotgun with No. 6 shot. Firearms cannot be discharged in many urban areas due to discharge regulations. Gray and fox squirrels are game animals in most states, and lethal control may require a permit. Often state regulations allow homeowners to take (kill) squirrels causing property damage. If there is any question, check with your state wildlife agency.
Gray and fox squirrels are classified as game species in most states, so trapping permits may be required from your state wildlife agency. Place traps near den holes or on travel routes. Do not rely on bait to overcome poor location of traps. Most traps will be placed off the ground, so make sure they are secured to something solid. Use at least 3 traps for gray and fox squirrels, and 5 or more for smaller squirrels. Remove competing food sources such as bird feeders.
In rescue situations, such as from chimneys or basements, consider on-site release of squirrels, provided the entrance to the structure has been secured.
Avoid translocation of tree squirrels because of the stress placed on both transported and resident squirrels, and concerns regarding the disease transmission. Many states do not allow the translocation of squirrels. Check with your state wildlife agency.
Carbon dioxide is the preferred method of euthanasia for tree squirrels. Squirrels expire relatively quickly in carbon-dioxide chambers. Shooting is also a good method for larger squirrels if it is safe and legal in your area.
Squirrel, NWCO, wildlife control, wildlife damage management