Fox Squirrel and Gray Squirrel
This squirrel is throwing himself into
the game of birdseed thievery.
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Most people don't pay much attention to tree squirrels. That is, until they decide to feed wild birds. Squirrels love the birdseed, particularly the meaty sunflower seeds. This might be fine if they weren't so greedy: "Yum, plenty of seed, so easy to get at, and all mine, mine, mine."
It's expensive to feed squirrels. Eventually, on behalf of our pocketbook, and the birds who aren't getting their fair share, the war of the humans and the squirrels commences. We try a method to keep the squirrels away, then another and another. We move the bird feeders here and there. We try baffles and wires and water spray. Embarrassingly, the humans lose at every turn. Anyone who's tried to outwit squirrels and has failed (which means most of us) will agree that squirrels seem smarter than humans! You have to admire their intelligence and determination. And, don't they seem to enjoy the challenge? The squirrels who keep challenging you are probably the Eastern Gray or the Eastern Fox, those most commonly found in a backyard wildlife habitat.
Squirrels are rodents belonging to the scientific order, Rodentia (row-DENCH-ee-uh), the largest group of mammals. This is a group of gnawing mammals who all have chisel-shaped teeth in common. To some people, squirrels look like big rats. They aren't rats, but, being rodents, they are related. Mice, beavers, prairie dogs, chipmunks and porcupines are members of this group, too.
Squirrels fall into one of three groups: tree squirrels, ground squirrels and flying squirrels. Flying squirrels, who seem rather exotic, don't actually fly. They glide. They have a fur-covered membrane that extends from ankle to wrist on each side of their body. By spreading their legs wide, they're able to glide from a higher perch to a lower one. They reportedly can glide the length of a football field from a 50-foot-high perch. Like other squirrels, they can also run on the ground and dash through trees.
In contrast to flying squirrels, who tend to be nocturnal, ground and tree squirrels are active during the day (diurnal). Ground squirrels spend their time on the ground and live in burrows. The most common urban squirrels are the Fox and the Gray tree squirrels, who are very similar in most respects, so the following applies to both species, unless otherwise noted.
Fox squirrels are named for the color of their fur. Their back is reddish-orange and the belly a paler shade of red or orange. Adults are 18-29 inches long, not counting the tail. The tail is about 12 inches. An adult weighs about 2 pounds.
Eastern Gray squirrels are also named for the color of their fur. Their belly is whitish, however, and in winter, the ears may be white. Their tail may be a lighter color, too. They're smaller than Fox squirrels -- about 14-20 inches long, with the tail 7-10 inches. The adult Gray weighs about 16-24 ounces.
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 southeastern part of their range. A black population of Fox squirrels lives in one small Kansas town, Marysville, and a totally white (but not albino) population of Gray squirrels lives in Brevard, North Carolina and other towns.
The Fox squirrel has 20 teeth and the Gray squirrel has 22. All squirrels have upper and lower incisor teeth that grow throughout their lives -- about 6 inches a year. The teeth would grow too long if they weren't regularly chiseled down by the rough, herbivorous diet they eat. They also habitually gnaw on things, like tree bark, and grind their teeth constantly, even when they sleep. The ears of tree squirrels are large and they have excellent hearing. Their vision is first-rate, too.
A squirrel's tail is fluffy and about the same length as his body. The tail isn't just for show; it serves squirrels in several ways: It shields them from rain, or from sunshine on a hot day when they sweep it up and over their back. It blankets them when they sleep, wrapped around their body. (As a matter of fact, the name "squirrel" derives from the Greek skia (shadow) and oura (tail): tail that casts a shadow.) The tail also acts as a stabilizer when they go airborne from branch to branch. It's something of a parachute if they fall and serves as a rudder when they swim. And it sometimes saves a life when a chasing predator catches a squirrel by the tail -- the fur, skin and some of the vertebrae will easily break off and the squirrel keeps on going. (The tail, however, doesn't grow back like that of lizards and amphibians, leading one to hope this doesn't happen too often to the same squirrel.)
Squirrels have four toes on their front feet and five on the back. Each toe has a strong claw. 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. They can leap, too: An Eastern Gray squirrel was observed leaping more than 8 feet to a platform holding seeds. With a predator in pursuit, a squirrel's hard to catch once he gets to a tree. On the ground, they can run and dodge, but they're much more vulnerable. Squirrels seem to be able to nimbly negotiate almost everything (think of telephone lines). However, they do fall sometimes. One extremely lucky squirrel fell 100 feet without injury.
Range and habitat
The Eastern Fox squirrel and Eastern Gray squirrel inhabit the eastern half of the U.S., as well as the West wherever they've been introduced. There's also a "Western" Gray squirrel (Sciurus griseus), but he's a shy species of the West who lives mostly in the forests of mountainous or hilly regions.
The Fox and the Gray, being tree squirrels, live where there are trees. The Fox spends the most time on the ground and is the one most tolerant of a prairie-type environment with fewer trees. The Gray squirrel likes heavier tree coverage. Fox and Gray squirrels have a home territory of a few acres, where they spend their lives. You may have several squirrels living in your yard in overlapping territories.
Fox squirrel in his
Gray squirrels and Fox squirrels are mostly solitary animals. Females share a den with offspring while raising them, and squirrels will sometimes share a den in cold weather. Otherwise, they stay alone. They're most active in the early morning and late afternoon. They rest in the afternoon, sometimes in a day nest, or they may just lay atop a tree branch. They're generally early to bed, usually curling up in a tight ball well before sunset. Squirrels are at their most active in the fall, when hints of coming cold weather ignite a need to find and stash winter food. At this time they begin to eat more, too, packing on fat to help carry them through the winter. Squirrels don't hibernate; in very cold weather they will sometimes spend several days curled up in their nest.
As you may have personally experienced, squirrels can be very vocal. Many of us have been subjected to their scolding: a loud, staccato, clucking sound accompanied by a herky-jerky, flicking tail and “get out of 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 vocalizations are used to warn of nearby predators, in courtship and in territorial displays. Infant squirrels being fed or touched by wildlife rehabilitators 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.
Another way squirrels communicate is 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 his scent trail.
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 (their coloring blends in with tree bark). 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 two.
How smart are squirrels? Very. For a fun example of squirrel intelligence, watch this video on youTube.com. It shows a squirrel using his teeth to lift the pop-up spray head of a sprinkler system. The sprinkler is not operating, but each time the head is raised, it dispenses a little water, which the squirrel drinks. He repeats this again and again until his thirst is slaked.
Both Fox and Gray spend a lot of their life on the ground, either seeking food -- young shoots, buds, berries, fallen nuts and fruits -- or tending to food: They bury nuts in late summer and fall to serve as food stores through the winter. (They reportedly can smell buried nuts under a foot of snow.) Although squirrels are considered to be herbivores, they supplement their nutty, veggie, fruity diet with a small quantity of insects, bird eggs and even nestlings, mostly while raising their young.
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 and planters.
Cover and nesting
Squirrels prefer to nest in a hollow tree or other location that offers cozy protection. They have a thick coat of fur and, in winter, it keeps them pretty toasty. But, it isn't waterproof. Those leafy nests (called dreys) we see clinging to tree branches are built for temporary use. If a squirrel can't find a suitable hollow tree or other sheltered den site, especially in winter, he'll build a drey. For winter the drey is heavily constructed with thickly interwoven twigs. He creates an entrance through the side so that once inside he has a roof over his head. In the warmth of summer, the drey might be built as nothing more than a simple small saucer. The squirrels are also known to nest in chimneys, attics and other places that offer protection from predators and weather.
Depending on the climate, December, January or February is a busy month for squirrels, with much chasing up, down and across tree branches and leaping from tree to tree. It's the first of twice-a-year mating rituals. The males compete for females by trying to chase each other away. They also chase females, hoping to be the final suitor. Gray squirrel males start following a female five days before estrus (the time she is willing to mate and able to conceive.) They have a very narrow window of opportunity, as she'll be in estrus only a few hours. The Fox female, on the other hand, can mate anytime, but her mating peaks in December and June. Both species may mate again from April through June. Both male and female squirrels may mate with more than one partner.
The mother of this baby Fox Squirrel
built her nest in a Wood Duck nesting
The female prefers a den of dry leaves in a hollow tree 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. 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 just as though she'd planned it that way.
About 45 days after mating, the female gives birth to as many as seven (usually three) blind, deaf and mostly naked babies, 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. These 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. 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. (Adult squirrels are very clean, spending time with personal grooming every day. Should their nest become contaminated with parasites, they move.)
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 support them 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 gray squirrels (who are gregarious), once they have left the family group they might continue to live in their mother's territory, providing it can support the extra population. 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. Fox and Gray squirrels raised in captivity live to be about 18 years old. In the wild they live six to 12 years.
Predators include hawks, foxes, coyotes and an occasional house cat. Automobiles kill thousands, perhaps millions, a year.