Do you feed squirrels? Would you rather be feeding birds? Across the nation, little battles rage between people and the squirrels that steal from their feeders at warp speed. We try first one method and then another and another, with the squirrels usually the victors! The most common of the thieving squirrels in the United States are Fox Squirrels and Gray Squirrels. Both are native to the eastern half of the United States but have been introduced into western areas. Much of what follows applies to both squirrel species. Where there are differences, it will be noted.
|Eastern Fox: S. niger|
|Eastern Gray: S. carolinensis|
The Fox Squirrel (or Eastern Fox Squirrel) and the Gray Squirrel (also known the Eastern* Gray Squirrel) are rodents in the family Sciuridae. Their suborder, Sciurinae, includes other tree squirrels, as well as ground squirrels, chipmunks, and marmots. There are 10 subspecies of Fox Squirrels and five of Gray Squirrels.
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. Gray Squirrels prefer dense stands of trees. The two generally don’t share the same habitat, but when they do, they don’t interbreed. They 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.
The earliest known squirrel fossil, which looks similar to today’s flying squirrels, is 47 to 33 million years old. That places it in the Eocene Epoch when Earth was covered by forests.
The Fox Squirrel is typically brown-grey to brown-yellow to brown-orange, with a brownish-orange underside. But, it has the most variable coloration of any squirrel in the world, with subspecies that produce dazzling exceptions. Some small cities, including Marysville, Kansas, have an all-black population. There are Fox Squirrels with a patterned dark-brown body, or a black face with a white nose, or other variation. Whatever the color, they all shed their hair twice a year, summer and fall.
The Fox Squirrel is the largest tree squirrel native to North America. It’s 18–29 inches long (46–74 cm), plus a tail length of 8–13 inches (31 cm) and weighs 1.1–2.2 pounds (31.2–62.4 g).
The Gray Squirrel is predominately what its name announces–gray–although some have a brownish tinge. Its belly is whitish, and sometimes its tail may be a lighter color, too. In winter its ears may be white. An exception among Gray Squirrels is an all-white (not albino) population in Brevard, North Carolina and a few other cities.
The Gray Squirrel is considerably smaller than the Fox Squirrel, at just 9.1–11.8 inches long (23.1–30.0 cm), plus a 7.5–9.8-inch tail (17.8 to 25.4 cm). It weighs about 14–21 ounces (400–600 g). Like the Fox, it sheds its hair twice a year, in spring and fall.
There’s a beautiful an all-black mutation of both the Fox and Gray squirrels that inhabits some areas of the Midwest and Northeast.
Tree squirrels have small, upright ears and their mouth is located slightly on the underside of their face. Sensitive whiskers dot their muzzle, as well as other areas of their face. Large, black eyes are set high on the head and slightly to the sides. This gives the squirrels a wide side-view but prevents them from seeing directly in front.
They have 20 teeth. Four of them–orange-tinted front teeth (two upper and two lower, called incisors)–grow continuously, about 6 inches (15 cm) a year. That might conjure up the impression of terrifying, potentially five-foot-long teeth, but we don’t see that because they “file” them. Squirrels regularly gnaw on tough surfaces like wood to keep their teeth at a proper length and alignment. To do otherwise means death because eventually, they can’t eat or become grievously injured.
Another interesting thing about the incisors is that the front surface 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.
A tail for all seasons
Their long, fluffy tail is like the squirrel version of a Swiss Army Knife, having multiple uses! When they sweep it up and over their back, it’s a slicker when it rains. On a hot, sunshiny day it’s an umbrella. It covers them when they sleep and provides a blanket of warmth in cold weather. The word “squirrel,” in fact, comes from Ancient Greek skiouros, meaning “shadow tail.”
Their tail acts as a stabilizer when a squirrel goes 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 (it doesn’t grow back).
But, that’s not all! It also communicates. Fear, anger, annoyance, aggression, and other emotions are conveyed by its position, whether its held straight up, straight back or curled over the body.
Speed and agility
Squirrels have hairy feet. Four toes (sometimes called fingers) are on the front. The back feet, which are longer, have five toes. Their claws are long, curved and extremely sharp and their hind legs are strong. Their ankles are double-jointed, which allows them to turn 180 degrees. All in all, these critters can perform some pretty fancy footwork. On the ground, they’re fast and can quickly dodge away from predators. They can run at up to 20 miles per hour (32 km) and leap up to 8 feet (2.4 m). (They do fall sometimes, and one lucky squirrel fell 100 feet (30.5 m) without apparent injury.) If they must swim, they can, and do it well.
The squirrels have well-developed senses of taste, hearing, eyesight, and touch. They also have such a keen sense of smell they can detect a buried nut under a layer of snow.
Their sense of touch is assisted by sensitive whiskers (vibrissae) on their face that help them feel around in the dark. There are sensitive hairs on the forepaws, just above the wrists, and females have a sensitive single hair on each nipple, eight in all.
How smart are squirrels? Very–just ask anyone who’s tried to keep them off bird feeders! They develop strategies to outwit even complex mechanisms. They’re also relentless; it takes a lot for them to give up.¹ A 2015 study of Gray Squirrels showed they’re quick learners and capable of adapting their behavior to gain access to food. Other research shows they’re 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 a convincing example of squirrel smarts
Fox Squirrels are diurnal–they’re active through the day and sleep at night. Gray Squirrels, on the other hand, are mostly crepuscular, which means they’re most active in early morning and late afternoon.
Both species are mostly solitary. Adults will sometimes share a den in cold weather and females share one with their offspring while raising them. Otherwise, they don’t often interact, other than to congregate at bird feeders. Neither of the two species is aggressively territorial, but there’s a dominance hierarchy, and they’ll defend their nests and food.
The 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.
Fall is when they’re most active, as hints of coming cold weather ignite a need to find and bury winter food. They also begin to eat more, 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.
When they feel threatened, the squirrels often simply remain motionless expecting their coloration to camouflage them in their surroundings. Their safest place is in a tree, so that’s where they’ll head first if they must run.
One of their strategies is to keep a vertical object between themselves and a predator. Perhaps you’ve experienced this trick yourself when approaching a squirrel that’s clinging to a fat tree trunk. As you move around the tree, the squirrel does too, so the trunk always stands between the two of you. If caught, squirrels will claw and bite. They can also swim if they must.
Fox Squirrels and Gray Squirrels are vocal. Have you been the target of their scolding? It’s a loud, staccato, clucking sound accompanied by a fast, swishing 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 Gray Squirrels, a quacking sound.
The squirrels also vocalize to warn of nearby predators, to announce when the danger has passed, in courtship, and in territorial displays. Chattering their teeth is a show of aggression and they may make a loud shrieking sound when startled or frightened. 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 as they’re tended by their mother. Learn more about squirrel-talk here and here.
Another form of communication is with scent; they mark their territories with urine. One research study has shown that squirrels can identify a relative by their scent trail.
Nesting and cover
The 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 hollow, roughly sphere-shaped nest, constructed about 30 feet (9 m) above the ground. It’s made of thickly interwoven twigs a squirrel has just gnawed off a tree. The twigs are soft and pliable with leaves still attached, which makes them easily manipulated. When the twigs die, they harden into position, providing sturdiness and resistance to wind. The drey changes from green to brown as the leaves dry up.
Inside, a drey is lined with finer material, such as grass, moss, dried leaves, and shredded bark. The opening (sometimes two, so that there’s an escape exit) is usually on the underside and oriented toward the trunk. This configuration means it has a “roof” to keep rain out. Should it become contaminated with parasites, the squirrel moves out. In fact, it’s common for them to have one or more spare dreys. Eventually, they fall apart. In the heat of summer, a squirrel might instead construct a simple saucer-like nest.
Fox Squirrels mate twice a year, in mid-December to early-January and in June. 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 each other, hoping to drive competitors away. They know when a female is ready to mate by her scent, and they may mate with more than one in a season. They play no other role in the lives of their offspring.
A pregnant female prefers a den in a tree hollow. If she must, she’ll build a drey in the fork of a tree or other place she considers suitable. She gives birth to as many as seven (usually three) very pink, blind, deaf and mostly naked babies, each weighing about 0.5-ounce (14 gm). Their only advantage is the whiskers on their head, which they use to find their mother in the dark nest.
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 plenty of care. She spends 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. Her nest stays clean, too, because she removes the babies’ excrement.
As juveniles, the squirrels learn social skills and how to fend for themselves. They play-fight and chase each other around. This helps develop coordination and strength which they’ll need for survival. They practice mounting behavior and also groom each other.
Up to the treetops they go and down to the ground. They learn which trees offer food, the tastiest ones 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.
The squirrels spend a lot of their life on the ground, either seeking food or tending to food. Although considered to be herbivores and aficionados of nuts, they supplement their diet with a few insects, bird eggs, and even nestlings, mostly while raising their young. They also eat seeds, corn, tree sap, buds, twigs, inner tree bark, fungi, and osage orange and other fruits.
In late summer and fall, they bury nuts to serve as food stores through the winter. When winter comes, they dig them up, as needed. The nuts aren’t cached all in one spot, and while they probably remember where some are, the squirrels may locate most of them by smell. The nut one squirrel digs up might well have been buried by an another. It’s through this method of storing 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 only beginning to develop. At this time, the squirrels rely heavily, to the great frustration of tree-lovers, on tree buds and sometimes tree bark.
Fox Squirrels raised in captivity have lived up to 18 years. In the wild, females may live 12 years or more, while males die younger from various causes. Gray Squirrels live an average of six years in the wild but can live up to 20 years in captivity. In the case of both, most die before they become adults.
Predators of squirrels include hawks, foxes, coyotes, and house cats. Vehicles kill thousands, perhaps millions, a year. Some Fox Squirrel subspecies 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. Read online reviews before purchasing.
* Top photo: Eastern Gray Squirrel. (Troydj / Wiki cc by-sa 3.0)