Do you feed squirrels in your yard? Would you rather be feeding birds? Across the nation, little battles rage between people and the squirrels that empty their 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!
The most common thieving squirrels in the U.S. are the Eastern Fox Squirrel and the Eastern Gray Squirrel. You’ll get to know them here, but we can’t promise it will teach you how to outsmart them! Both species are native to the eastern half of the U.S. but have been introduced into western areas.
The Eastern Fox and the Eastern Gray Squirrels are rodents in the scientific order, Rodentia (row-DENCH-ee-uh), which is the largest group of mammals. They’re in the family Sciuridae and suborder Sciurinae, which includes tree squirrels, ground squirrels, chipmunks and marmots. Their genus is Sciurus.
“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 was similar to today’s flying squirrels.
Today there are 10 subspecies of the Eastern Fox Squirrel and five subspecies of Eastern Gray Squirrels. They’re known as tree squirrels because they live mostly among trees, as opposed to ground squirrels, which live primarily on or in the ground.
Eastern Fox Squirrels, Sciurus niger, may have been named for their reddish-orange hair and bushy tail, resembling that of a fox. They’re the largest tree squirrels native to North America, 18 to 29 inches long (45.7 to 73.7 cm), not counting their tail, which is about 12 inches long (30.5 cm). They weigh about two pounds (0.9 kg).
Eastern Gray Squirrels, Sciurus carolinensis, are predominately gray, but 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. They’re about 14 to 20 inches long (35.6 to 73.6 cm), plus a 7- to 10-inch tail (17.8 to 25.4 cm). They weigh about 16 to 24 ounces (0.5 to 0.7 kg).
Some extreme color variations occur 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 few other places. And a totally white (but not albino) population of Eastern Gray Squirrels lives in Brevard, North Carolina, and other towns. Both species molt (shed) their hair twice a year, in spring and fall (hair on the ears and tail may molt only once a year).
Squirrels’ eyes are large, set high on their head and slightly to the sides. This gives them a wide field of vision.
They have four sets of long touch-sensitive whiskers called vibrissae on their face. The vibrissae help squirrels feel what’s around them in the dark and are of particular benefit to their babies, which are born blind, but have whiskers.
There are four sets of vibrissae: alongside the nose, one above the eyes, one below the eyes and one under the jaw. Females have an additional single hair on each nipple, eight in all. Also, squirrels’ forepaws, just above the wrists, have sensitive hairs.
Squirrels have 20 teeth. Their four orange-tinted front teeth (incisors), two uppers and two lower, grow continuously throughout their lives, about 6 inches a year. They must be kept to a correct length and properly aligned, so squirrels constantly gnaw on tough things, such as tree bark, and they 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 cause a squirrel’s death, either by penetrating its skull or jaw, or by keeping it from eating altogether.
A tail for all seasons
Their long, fluffy tail is like the squirrel version of a Swiss Army Knife, providing what they need for multiple purposes! When they sweep it up and over their back, it’s a slicker when it rains and an umbrella on a hot, sunshiny day. It covers them when they sleep and provides a blanket of warmth in cold weather.
The tail acts as a stabilizer when the squirrels go airborne between trees or branches. If they fall, it’s a mini-parachute, and it’s 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).
The tail is also a communicator. Its position signals a state of mind. Depending on its position — held straight up, straight back or curled over the body — it indicates fear, anger, annoyance, aggression and other emotions.
Tree squirrels have hairy feet with four toes (sometimes called fingers) on the front and five toes on the back. Their claws are long, curved and extremely sharp. Their ankles are double-jointed, which enables them to turn 180 degrees. This, combined with strong hind legs, helps them move nimbly up and down trees. They can negotiate just about anything, and leap up to 8 feet (2.4 m). (They do fall sometimes — one lucky squirrel fell 100 feet (30.48 m) without apparent injury.)
On the ground, they’re fast and can quickly dodge from predators, too, but they’re still vulnerable. Once they get to a tree, they’re much harder to catch.
Squirrels have well-developed senses of smell, taste, hearing, eyesight and touch. Their most important one is smell, for finding food. They can detect a buried nut under a layer of snow. They also use their sensitive vibrissae for touch, like a cat does.
How smart are squirrels? Very — just ask anyone who’s tried to keep them off of bird feeders! They can defeat the best efforts of people to keep their feeders from being raided. Squirrels develop strategies to outwit even complex mechanisms. They’re also relentless; it takes a lot for them to give up.¹ A 2015 study² of Gray Squirrels showed they’re quick learners and capable of adapting their behavior to gain access to food. Other research shows they seem to be able to interpret the intention of others — pretending to cache nuts when they know they’re being watched, but then hide them elsewhere. Here’s an entertaining example of squirrel smarts
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 often, other than to congregate at bird feeders. Neither of the two species is territorial, but there’s a dominance hierarchy. They establish it by showing aggression; for instance, nipping another squirrel or by chasing it away.
Eastern Fox Squirrels are diurnal — they’re active through the day and sleep at night. Eastern Gray Squirrels, on the other hand, are mostly crepuscular, which means they’re most active in early morning and late afternoon. Both squirrels spend their inactive time in their nest, or they may just lie atop a tree branch. They’re very clean and spend time each day on personal grooming. They generally go to bed early, curling into a tight ball well before sunset.
Squirrels are 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 lots of fat to help carry them through the winter. They don’t hibernate, even in frigid weather, but they will sometimes spend several days at a time curled up in their nest.
Tree squirrels protect themselves first by running — as fast as 20 miles per hour (32 km). If they must swim, they can — and do it well. Often they simply remain motionless to avoid detection, expecting their coloring to blend 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 experienced this maneuver yourself when approaching a squirrel that’s clinging to a fat tree trunk. As you move around the trunk, the squirrel does too, so the trunk always stands between you two.
Tree squirrels protect themselves first by running — as fast as 20 miles per hour. If they must swim, they can — and 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 that’s clinging to a fat tree trunk. As you move around the trunk, the squirrel does too, so the trunk always stands between you.
Eastern Fox Squirrels and Eastern Gray Squirrels are 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 Eastern 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 has 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. The squirrels 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 sweltering 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 their scent trail.
Another method of communication is with their tail. How it’s held says a lot. If a squirrel is flashing its tail, for example, it’s showing alarm or aggravation. If the disturbance or danger is great, it’s accompanied by vocalizations to warn other squirrels of danger. A tail’s position can also signify relaxation, curiosity or other states of mind.
Nesting and cover
Tree squirrels prefer to build a nest in a tree hollow, chimney, attic, or other location that offers cozy protection from predators and weather. Lacking that, they make 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 harden into position and are very wind-resistant.
A drey is built roughly in the shape of a sphere, about one foot or more in diameter. Inside, it holds finer material, such as grass, moss or shredded bark. The opening (sometimes two, for an escape exit) is usually on the underside and oriented toward the trunk. This configuration means the drey has a “roof” to keep rain out. In the warmth of summer, the drey might be built more like a simple small saucer. Should their nest become contaminated with parasites, they move. Eventually, dreys fall apart.
Eastern Fox Squirrels mate twice a year, in mid-December to early January and in June. Eastern Gray Squirrels mate twice a year, December to February and May to June. Mating occurs a bit later in colder climates. For both species, the gestation period is 44 to 45 days.
Mating begins with males chasing females, each one hoping to be the final suitor. Males also chase other males, hoping to drive them away. They can determine when a female is ready to mate by her scent, and they may mate with more than one female in a season.
A pregnant female prefers a nest of dry leaves in a tree hollow. 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 material she can find.
Females give birth to as many as seven (usually three) blind, deaf and mostly naked babies, each weighing about a half-ounce (14 gm). Their skin is very pink and their only adornment is their vibrissae, or whiskers, which are small hairs sprouting from several spots on their head.
In about three weeks, the infants begin to grow hair, and their ears, which were flat at birth, stand 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, which helps develop coordination and strength, which they’ll need for survival. 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 ones 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, but, more and more they yearn for a life alone. Males of both species are more likely to disperse to new territories than females.
Tree squirrels spend a lot of their life on the ground, either seeking food or tending to food. Although considered to be herbivores, they supplement their diet with a few insects, bird eggs, and even nestlings, mostly while raising their young. In late summer and fall, they bury nuts to serve as food stores through the winter.
In winter, squirrels dig up nuts as they need them. The nuts aren’t buried all in one spot, and while they probably remember where some of them are, they may just smell most of them. The nut one squirrel digs up might well have been buried by a different squirrel. It’s through this method of caching nuts that squirrels help to reforest areas, as more nuts are buried than retrieved.
Food becomes scarce by late winter. Some buried nuts haven’t been found, and other sources of food are just beginning to develop. At this time, squirrels rely heavily on tree buds and sometimes tree bark.
In addition to nuts, the squirrels eat seeds, corn, tree sap, buds, twigs, inner tree bark, fungi and osage orange and other fruits.
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 states, so either one may live in your yard. They generally don’t share the same habitat, though (when they do, they don’t interbreed.)
Eastern Fox Squirrels spend much of their time on the ground searching for food and prefer woodlands next to openings. They’re tolerant of prairie-type environments. Eastern Gray Squirrels prefer dense stands of trees.
Both species 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 raised in captivity have lived up to 18 years. In the wild, their average life expectancy is 12.6 years for females and eight years for males. Eastern Gray Squirrels live an average of 12.5 years in the wild and up to 20 years in captivity. In the case of 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.
¹ Well-positioned bird feeders and baffles, as well as some squirrel-proof feeders have proven to be effective.
² Grey squirrels are quick learners, study shows
* Top photo: Eastern Gray Squirrel. (Troydj / Wiki cc by-sa 3.0)