Do you feed squirrels in your yard? Would you rather be feeding birds? Across the nation, little battles rage between humans and the squirrels that empty bird feeders at warp speed. We try first one method and then another and another. We move the feeders here and there. We try baffles and wires and automatic water sprayers. Anyone who’s tried to outwit squirrels and failed (that would be most of us) will agree that their intelligence and persistence are frustrating. It wouldn’t be quite so bad if they would share. But, no, it’s all “me, me, me.” They seem to enjoy the challenge, too — we can almost hear them sniggering as we hang the latest “squirrel proof” feeder!
Much of this article pertains to all tree squirrels in general, but we’ve included specific information about the Eastern Fox Squirrel (Sciurus niger) and the Eastern Gray Squirrel (Sciurus carolinensis) — they’re the most common species in urban neighborhoods. Both species are native to the eastern half of the U.S., but have been introduced into western areas.
Squirrels are rodents belonging to the scientific order, Rodentia (row-DENCH-ee-uh), the largest group of mammals. The squirrel family is named Sciuridae and includes tree squirrels, flying squirrels, ground squirrels, chipmunks, marmots and prairie dogs. “Squirrel” is derived from the Greek skiouros, meaning “shade tail,” a reference to their habit of covering their back with their tail. The earliest known squirrel dates back to the Eocene Epoch, 47 to 33 million years ago and is similar to today’s flying squirrels.
Eastern Fox Squirrels are the largest tree squirrels native to North America. They may have been named for their reddish-orange hair color and bushy tail, resembling that of a fox. Eastern Gray Squirrels are, as their name says, predominately gray. They may sometimes have a brownish tinge. Their belly is whitish, and in winter the ears may be white. Their tail may be a lighter color, too.
Some extreme color variations can be seen in both species, often particular to the region in which they live. For instance, a population of dark-headed, gray-backed Fox Squirrels lives in the Southeast. A black population of Fox Squirrels lives in one small Kansas town, Marysville, and a totally white (but not albino) population of Eastern Gray Squirrels lives in Brevard, North Carolina and other towns. Both species molt their hair twice a year, in spring and fall (the hair on ears and tail may molt only once a year).
Eastern Fox Squirrels are 18 to 29 inches long, not counting their tail, which is about 12 inches long. They weigh about two pounds. Eastern Gray Squirrels are about 14 to 20 inches long, plus a 7- to 10-inch tail. They weigh about 16 to 24 ounces.
Tree squirrels have a long, fluffy and very useful tail. When they sweep it up and over their back: It’s a slicker when it rains. It’s an umbrella on a hot, sunshiny day. It blankets them when they sleep. The tail acts as a stabilizer when they go airborne between trees or branches. If they fall, it’s a mini-parachute, and a rudder when they swim. It can save a life when a pursuing predator catches a squirrel by the tail — the fur, skin and some of the vertebrae will easily break off and the squirrel can keep on running away (it doesn’t grow back).
Eastern Fox Squirrels have 20 teeth. Eastern Gray Squirrels have 22 teeth (an extra molar on each side), which is more than any other squirrel species.
The squirrels’ four front teeth (incisors), two upper and two lower, are orange-tinted and grow continuously throughout the squirrels’ lives, about 6 inches a year. They keep them filed down to a correct length and properly aligned by gnawing constantly on tough things, such as tree bark, and even grind their teeth when they sleep. The front surface of the incisors is covered by hard enamel, while the back surface is dentin, which is softer. As a consequence, the back surface wears down faster than the front, producing chisel-shaped teeth. The gnawing behavior is imperative — overlong teeth will eventually kill them by penetrating their skull or jaw, or keep them from eating altogether.
Tree squirrels have hairy feet with four toes (some call them fingers) on the front and five toes on the back. Their claws are long, curved and sharp. Their ankles are double-jointed, allowing them to turn 180 degrees — this, combined with strong hind legs, helps them move nimbly up and down trees. On the ground, they’re fast and can run and dodge from predators, but they’re vulnerable. Once they get to a tree they’re much harder to catch. They can negotiate just about anything, and leap up to 8 feet. They do fall sometimes — one very lucky squirrel fell 100 feet without apparent injury.
Range and habitat
Eastern Fox Squirrels and Eastern Gray Squirrels are native to the eastern half of the U.S. Both species have been introduced into western areas of the U.S. and either one may live in your yard. They generally don’t share the same habitat. Eastern Fox Squirrels spend much of their time on the ground and prefer woodlands next to openings. They’re tolerant of prairie-type environments. The Eastern Gray Squirrel, on the other hand, prefers dense stands of trees. (There are Western Gray Squirrels (Sciurus griseus) also inhabiting the western states, but they’re shy and prefer forests at higher elevations.
Both the Eastern Gray Squirrel and Eastern Fox Squirrel have home territories of a few acres, where they spend their entire lives. You may have several squirrels living in your yard in overlapping territories.
Eastern Fox Squirrels and Eastern Gray Squirrels are primarily solitary animals. Adults will sometimes share a den in cold weather and females share a den with offspring while raising them, Otherwise, they don’t interact very often, other than to congregate at bird feeders.
Neither Eastern Fox Squirrels nor Eastern Gray Squirrels are territorial, but there’s a dominance hierarchy. They establish it by showing aggression; for instance, nipping another squirrel or by chasing. Young squirrels chase each other in a playful way, which helps them develop coordination and strength, which they’ll need for survival.
Eastern Fox Squirrels are diurnal, active in the daytime and sleeping at night. Eastern Gray Squirrels are crepuscular, mostly active in early morning and late afternoon. They rest in the afternoon, sometimes in a day nest, or they may just lie atop a tree branch. They’re generally early to bed, usually curling up in a tight ball well before sunset.
Tree squirrels are at their most active in the fall, when hints of coming cold weather ignite a need to find and bury winter food. At this time, they begin to eat more, too, packing on fat to help carry them through the winter. They don’t hibernate; in very cold weather they will sometimes spend several days curled up in their nest. Squirrels are very clean, daily spending time with personal grooming. Should their nest become contaminated with parasites, they move.
Tree squirrels protect themselves first by running — by one account as fast as 20 miles per hour. If they must swim, they can — and they do it well. Often they simply remain motionless to avoid detection, with their coloring blending into the background. If all else fails, they’ll claw and bite their attacker. Another strategy is to keep a vertical object between themselves and a predator. Perhaps you’ve seen this maneuver yourself when approaching a squirrel who’s clinging to a fat tree trunk. As you move around the trunk, the squirrel does too, so the trunk always stands between you.
How smart are squirrels? Very, just ask anyone who’s tried to keep them from bird feeders! Here’s an example — a squirrel using its teeth to lift the pop-up head of a lawn sprinkler to get water.
Eastern Fox Squirrels and Eastern Gray Squirrels are very vocal. Have you ever been the target of their scolding: a loud, staccato, clucking sound accompanied by a flashing tail and “get outta here” stare? They scold each other similarly, but have other forms of communication, too, including barks, whistles and, in the case of the Gray Squirrels, a quacking sound. Their vocalizations are used to warn of nearby predators, in courtship, and in territorial displays. Other calls announce when the danger is passed. Infant squirrels being fed or touched by wildlife rescuers are known to produce a purring sound, presumably something they would also do in the wild while being tended by their mother. They may also make a loud shrieking sound when startled or frightened. Teeth chattering is a sign of aggression. Learn more about squirrel-speak here and here.
Tree squirrels also communicate through scent marks they leave on branches. Their sweat glands, which leave a distinctive odor, are located on the bottom of their feet (on a very hot day, a squirrel walking across a sidewalk might leave damp paw prints.) They also scent branches with their urine or anal fluids to mark their territory. One research study has shown that squirrels can identify a relative by the scent trail.
Another method of communication is with tail-flashing, which indicates alarm. If the disturbance or danger is great, it’s accompanied by vocalizations to warn other squirrels of danger.
Tree squirrels spend a lot of their life on the ground, either seeking food — young shoots, buds, berries, fallen nuts and fruits, fungi, corn — or tending to food. Although considered to be herbivores, they supplement their diet with a small quantity of insects, bird eggs and even nestlings, mostly while raising their young, but also if struggling to find enough food. In late summer and fall, they bury nuts to serve as food stores through the winter. Favorite fall nuts include acorns, hickory nuts and walnuts.
In winter, squirrels dig up nuts as they need them. The nuts aren’t buried all in one spot and while it’s possible they remember where some of them are buried, they may just smell them. The nut one squirrel digs up might well have been buried by a different squirrel. It’s through this practice of caching nuts that squirrels help to reforest areas, as more nuts are buried than are retrieved. Next time you’re digging in your garden and find a buried nut, you’ll know it isn’t there by accident. It’s this behavior that’s also behind the holes we sometimes find in the disturbed soil of our flowerpots, planters and lawns.
Food for them becomes scarce in late winter and, especially, early spring. Buried nuts are beginning to germinate or are already eaten, other food sources are only just beginning to develop, and the squirrel population may be at a peak. At this time, they rely heavily on tree buds and sometimes tree bark.
Cover and nesting
Tree squirrels prefer to build a nest in a hollow tree or other sheltered location that offers cozy protection. Lacking that, they build a “drey.” A drey is a nest constructed with thickly interwoven twigs that are still soft and pliable, with green leaves still attached. When the twigs and leaves die, they hardened into position and are very wind-resistant. Eventually, they fall apart.
A drey is built roughly in the shape of a sphere, about one foot or more in diameter, with one or two openings. Inside, it holds finer material, such as grass, moss, shredded bark. The opening(s) is usually on the underside and oriented toward the trunk. This configuration means the drey has a “roof” to keep rain out. Sometimes there’ll be a second hole as an escape route. In the warmth of summer, the drey might be built more like a simple small saucer. One drey, constructed at the very tip of a Washington Hawthorne tree, couldn’t be missed: It was topped with a purple-colored silk flower the squirrel had found. Like a ship’s flag, it waved colorfully in the breeze. Tree squirrels are also known to nest in chimneys, attics and other places that offer protection from predators and weather.
Depending on the region, December through February are busy months for most species of tree squirrels. During the first of twice-a-year mating rituals, males are busy chasing females, each hoping to be the final suitor. They use scent to determine when a female is receptive. Males also chase males, hoping to drive each other away. Males may mate with more than one female in a season. The second mating season is May to June (younger mothers often breed only once, in the spring.)
Eastern Gray Squirrels are particularly challenged. Males begin following females five days before estrus (when a female is willing to mate and able to conceive), but have a very narrow window of opportunity — females are receptive for less than eight hours. Eastern Fox Squirrels, on the other hand, can mate anytime, although their mating peaks in December and June. For both species, most births occur in Mid-March and July.
The female prefers a nest of dry leaves in a tree den or, if she must, she’ll make a drey in the fork of a tree or other place she considers suitable. She lines the drey with leaves, moss, fur and just about any other soft thing she can find.
About 45 days after mating, she gives birth to as many as seven (usually three) blind, deaf and mostly naked babies, each weighing about a half-ounce. Their skin is very pink and their only adornment is their “vibrissae,” which are small hairs sprouting from several spots on their head and neck. Vibrissae are stiff and similar to whiskers; squirrels use them for touch, like a cat does. In about three weeks, the infants begin to grow hair, and their ears, which were laying flat at birth, open up. At four to six weeks their eyes open. By the seventh week, weaning will start, and by the tenth they’re fully weaned, ready to take on the world with a lifetime supply of quick wits and keen senses.
Until then, their mother shows them lots of care. She spends plenty of time in the den, even lying on her back to make it easier for them to nurse. She’ll aggressively protect them from predators and move them one-by-one to another location, if necessary. She fusses over them by keeping them clean and free of parasites. She keeps the den clean, too, by removing the babies’ excrement.
As juveniles, the squirrels learn social skills and how to fend for themselves. They play-fight and chase each other around, they practice mounting behavior, and also groom each other. They follow their mother up into the treetops and down to the ground. They learn what trees offer food, which are tasty to gnaw on, how to crack open a nut, how to judge when a limb is too flimsy to climb and how to escape predators. They stay with their mother for several weeks after they’re fully weaned, but, more and more, they yearn for a life alone.
If these youngsters are Eastern Gray Squirrels (which are gregarious), once they leave the family group they might continue to live in their mother’s territory, so long as it can support the extra population. Eastern Fox Squirrels, on the other hand, are solitary, except when in a reproductive phase. Males of both species are more likely to disperse to new territories than females.
Eastern Fox Squirrels raised in captivity have lived up to 18 years. In the wild, their average life expectancy is 12.6 years for females and 8 years for males. Eastern Gray Squirrels live an average of 12.5 years in the wild and up to 20 years in captivity. In both species, most die before they become adults.
Predators include hawks, foxes, coyotes and house cats. Automobiles kill thousands, perhaps millions, a year. Some subspecies of fox squirrels are endangered due to overhunting and forest destruction. Mange (a skin disease caused by parasitic mites) is another cause of population decline, especially during severe winters when squirrels keep more to their nests, where the mites proliferate.
Eastern Fox Squirrel at a glance:
Appearance: Reddish or orangish above, lighter on belly.
Eastern Gray Squirrel at a glance:
Appearance: Gray above, white below
*Top photo: Eastern Gray Squirrel. (Troydj / Wiki; cc by-sa 3.0)