|A squirrel is a small or medium-sized rodent of the family Sciuridae. In the English-speaking world, it commonly refers to members of this family's genera Sciurus and Tamiasciurus, which are tree squirrels that have large bushy tails, and are indigenous to Europe (but not Ireland), Asia and the Americas. Similar genera are found in Africa. The Sciuridae family also include flying squirrels, as well as ground squirrels such as the chipmunks, prairie dogs, and woodchucks. Members of the family Anomaluridae are sometimes misleadingly referred to as "scaly-tailed flying squirrels" although they are not closely related to the true squirrels.|
Etymologyσκιά; "shadow") and oura (ούρά; "tail"). Skiouros might be liberally translated as "That which makes a shade with its tail", or "That which sits in the shadow of its tail". The verb form (meaning "to hide or store") is first recorded in 1939.
The word squirrel, first attested in 1327, comes from the Old French ésqurial, which itself comes from the Vulgar Latin word scuriolus (squirrel), a variant of the Latin sciurus. Sciurus comes from the Greek word skiouros, a compound of skia (
Common squirrels include the Fox Squirrel (S. niger); the Western Gray Squirrel (S. griseus); the Douglas Squirrel (Tamiasciurus douglasii); the American Red Squirrel T. hudsonicus; and the Eastern Grey Squirrel (S. carolinensis), of which the "Black Squirrel" is a variant.
Unlike rabbits or deer, squirrels cannot digest cellulose and must rely on foods rich in protein, carbohydrates, and fat. Early spring is the hardest time of year for squirrels, since buried nuts begin to sprout and are no longer available for the squirrel to eat, as well as new food sources have not become available yet. During these times squirrels rely heavily on the buds of trees, in particular, those of the Silver Maple. Squirrels are omnivores; they eat a wide variety of plant food, including nuts, seeds, conifer cones, fruits, fungi, and green vegetation, and they also eat insects, insect larvae, eggs, and even small birds, smaller mammals, frogs, and carrion. In tropical areas, these foods often replace nuts.
Ground and tree squirrels are typically diurnal, while flying squirrels tend to be nocturnal -- except for lactating flying squirrels and their offspring, who have a period of diurnality during the summer.
Predatory behavior by various species of ground squirrels, particularly the thirteen-lined ground squirrel, has been noted. Bailey (1923), for example, observed a thirteen-lined ground squirrel preying upon a young chicken. Wistrand (1972) reported seeing this same species eating a freshly-killed snake. Whitaker (1972) examined the stomachs of 139 thirteen-lined ground squirrels, and found bird flesh in four the specimens and the remains of a short-tailed shrew in one; Bradley (1968), examining white-tailed antelope squirrels' stomachs, found at least 10% of his 609 specimens' stomachs contained some type of vertebrate, mostly lizards and rodents. Morgart (1985) observed a white-tailed antelope squirrel capturing and eating a silky pocket mouse.
Relationship with humans
Squirrels are generally clever and persistent animals. In residential neighborhoods they are notorious for eating out of bird feeders, digging in potted plants either to bury or recover seeds, and for inhabiting sheltered areas including attics. While many companies sell bird feeders which are supposedly "squirrel-proof", very few of them really are. Although expert climbers, and primarily arboreal, squirrels also thrive in urban environments that are largely free of trees.
Squirrels are sometimes considered pests because of their propensity to chew on various edible and inedible objects. This characteristic trait aids in maintaining sharp teeth, and because their teeth grow continuously, prevents over-growth. Homeowners in areas with a heavy squirrel population must keep attics and basements carefully sealed to prevent property damage caused by nesting squirrels. (A squirrel nest is known as a "drey", especially in Britain.) Some homeowners resort to more interesting ways of dealing with this problem, such as collecting and planting fur from pets (such as domestic cats and dogs) in attics. This fur will indicate to nesting squirrels that a potential predator roams and will encourage evacuation. Fake owls and scarecrows are generally ignored by the animals, and the best way to prevent chewing on an object is to coat it with something to make it undesirable: for instance a soft cloth or chili pepper paste or powder. Squirrel trapping is also practiced to remove them from residential areas.
Squirrels can be trained to be hand-fed. Because they are able to cache surplus food, they will take as much food as is available. Squirrels living in parks and campuses in cities have learned that humans are typically a ready source of food. Hand feeding is not recommended, however, because squirrels may carry plague or other animal-borne diseases. Even if they do not carry disease, they often have a hard time telling fingertips from food, and bites are painful. Although rare, squirrels are sometimes kept as household pets, provided they are selected young enough and are hand raised in a proper fashion. They can be taught to do tricks, and are said to be as intelligent as dogs in their ability to learn behaviors. In these cases, a large cage with ample access to water and a balanced diet with good variety will keep a pet squirrel healthy and happy. As a pet, the owner must be aware of "spring fever" at which time a female pet squirrel will become very defensive of her cage, thinking of it as her "drey" and will become somewhat aggressive to defend the area.
Squirrels are often the cause of electricity outages. The animals will enter transformers or capacitors looking for food. The squirrels are then electrocuted and cause a short circuit that shuts down equipment. Squirrels have brought down the high-tech NASDAQ stock market twice and were responsible for a spate of power outages at the University of Alabama. They will often chew on tree branches to sharpen their teeth but cannot tell the difference between a tree branch and a live power line. Rubber plates (squirrel guards) are sometimes used to prevent access to these facilities.
Squirrels were responsible for 177 power outages in Lincoln, Nebraska, in 1980, which represented 24% of all outages. Estimated annual costs were $23,364 for repairs, public relations, and lost revenue. In Omaha, in 1985, squirrels caused 332 outages costing at least $47,144. After squirrel guards were installed over pole-mounted transformers in Lincoln in 1985, annual costs were reduced 78% to $5,148.
Urban squirrels have learned to get a great deal of food from over-generous humans. One of the more common and inexpensive foods fed to squirrels is peanuts. Recent studies however have shown that raw peanuts contain a trypsin inhibitor that prevents the absorption of protein in the intestine. Dr. James K. Kieswetter of Eastern Washington University suggests using roasted peanuts instead. However, wildlife rehabilitators in the field have noted that neither raw and roasted peanuts or sunflower seeds are good for squirrels, since they are deficient in several nutrients needed. This type of deficiency has been found to cause Metabolic Bone Disease, a somewhat common ailment found in malnourished squirrels.
Hunting and food
Until recent times, squirrel meat was considered a favored meat in certain regions of the United States where it can be listed as wild game. This is evidenced by extensive recipes for its preparation found in cookbooks including older copies of The Joy of Cooking. Squirrel meat can be exchanged for rabbit or chicken in recipes although squirrel meat is more tender than the latter. Squirrels can often become prey to different dogs that have the speed and agility to catch them. Dauchsunds are among some of these. Its light red or pink flesh has only a slight game taste. In many areas of the U.S., particularly areas of the American South, squirrels are hunted for food.
Despite periodic complaints about the animal as a pest, general public opinion towards the animal is favorable, thanks to its agreeable appearance, intelligence and its eating styles and habits. Squirrels are arguably the most successful wild urban animal species. Squirrels are popular characters in cartoons and children's books, such as the works of Beatrix Potter, Redwall, the squirrel Pattertwig in C.S. Lewis's book Prince Caspian, the Starwife and her subjects from Robin Jarvis's Deptford novels, Scrat from Ice Age, Slappy Squirrel of Animaniacs, Sandy Cheeks from Spongebob Squarepants, Hammy from Over The Hedge, Benny in The Wild, Rodney from Squirrel Boy, and Rocky, Bullwinkle's partner in adventures.
Albino squirrels are thought by some to be a source of good luck. The Albino Squirrel Preservation Society was founded at the University of Texas at Austin in 2001, and its sister chapter at University of North Texas petitioned for an election to name their albino squirrel as the university's secondary mascot (the election narrowly failed)..
Olney, Illinois, is home of the world's largest known albino-squirrel colony. Kenton, Tennessee, is home to about 200 albino squirrels. Brevard, North Carolina and Marionville, Missouri have a substantial population of white (not albino) squirrels. Western Kentucky University has a locally famous population of white squirrels. Exeter, Ontario in Canada is known for having non-albino white squirrels, believed to be the result of a genetic mutation in the early 20th century. White squirrels are also commonly seen in Dayton, Ohio and at the main campus of The Ohio State University in Columbus, Ohio.
The Fox Squirrel (Sciurus niger) is the largest species of tree squirrels native to North America. They are also sometimes referred to as the Stump-eared Squirrel, Raccoon Squirrel, or Monkey-faced Squirrel. They are sometimes mistaken for Eastern Gray Squirrels by casual observers in those areas where both species co-exist, despite the differences in size and coloration.
The Fox Squirrel's natural range extends throughout the eastern United States, excluding New England, north into the southern prairie provinces of Canada, and west to the Dakotas, Colorado, and Texas. They have been introduced into Northern California. While very versatile in their habitat choices, fox squirrels are most often found in forest patches of 400,000 square meters or less with an open under story, or in urban neighborhoods with trees. They thrive best among trees such as oak, hickory, walnut and pine that produce winter-storable foods like nuts. Western range extensions in Great Plains regions such as Kansas are associated with riverine corridors of cottonwood. A subspecies native to several eastern U.S. states, the Delmarva fox squirrel, Sciurus niger cinereus, is a listed endangered species.
Fox Squirrels depend primarily on tree seeds for food, but they are generalist eaters and will also consume buds and fruits, cultivated grain, insects, birds' eggs, and small lizards. Cannibalism has been reported, but should be considered very rare. In their regular diet of nuts, fox squirrels are classic scatter-hoarders that bury caches of nuts in dispersed locations, some of which are inevitably left un-retrieved to germinate.
Fox Squirrels are strictly diurnal, non-territorial, and spend more of their time on the ground than most other tree squirrels. They are still, however, agile climbers. They construct two types of homes called "dreys", depending on the season. Summer dreys are often little more than platforms of sticks high in the branches of trees, while winter dens are usually hollowed out of tree trunks by a succession of occupants over as many as 30 years. Cohabitation of these dens is not uncommon, particularly among breeding pairs.
Fox Squirrels are also known for being living fossils, skeletally very similar to remains of the oldest-known squirrel, Protosciurus, from the late Oligocene and early Miocene epochs.
The Douglas Squirrel, Tamiasciurus douglasii, is a pine squirrel found in the Pacific coastal states and provinces of North America. It is sometimes known as the Chickaree or Pine Squirrel, but since Chickaree is also used for the American Red Squirrel and Pine Squirrel for the genus Tamiasciurus, these alternative names are better avoided. The Native Americans of Kings River called it the "Pillillooeet", in imitation of its characteristic alarm call .
John Muir described the Douglas Squirrel as "by far the most interesting and influential of the California sciuridæ". It is a small, lively, bush-tailed tree squirrel, enchanting to watch. Adults are about 33 cm in length (including its tail, which is about 13 cm long), and weigh between 150 and 300 grams. Their appearance varies according to the season. In the summer, they are a grayish or almost greenish brown on their backs, and pale orange on the chest and belly, while legs and feet appear brown. In the winter, the coat is browner and the underside is grayer; also, the ears appear even tuftier than they do in summer. Like many squirrels, Douglas Squirrels have a white eye ring.
Douglas Squirrels live in coniferous forests, from the Sierra Nevada mountains of California northwards to coastal British Columbia. They prefer old-growth or mature second-growth forest, and some authors regard them as dependent on its presence. They are active by day, throughout the year, often chattering noisily at intruders. In summer nights, they sleep in ball-shaped nests that they make in the trees, but in the winter they use holes in trees as nests. They are territorial; in winter, each squirrel occupies a territory of about 10,000 square meters, but during the breeding season a mated pair will defend a single territory together. Groups of squirrels seen together during the summer are likely to be juveniles from a single litter.
Douglas squirrels mostly eat seeds of coniferous trees such as Douglas Fir, Sitka Spruce and Shore Pine, though they do also eat acorns, berries, mushrooms, the eggs of birds such as Yellow Warblers, and some fruit. Unlike many other types of tree squirrel, they lack cheek pouches in which to hold food. They are scatter hoarders, burying pine cones (which they cut from the trees while green) during the autumn. They often use a single place, called a midden, for peeling the scales off cones to get at the seeds. The discarded scales may accumulate for years, into piles more than a meter across as the same site is used by generations of squirrels. Their predators include American Martens, Bobcats, domestic cats, Northern Goshawks, and owls; although they quickly acclimatized to human presence, humans can be a threat to them, through robbing of their cone caches to find seeds for tree cultivation and through the destruction of old growth forest. However, the squirrels' numbers appear to be unaffected by commercial thinning of forests.
American Red Squirrel
The North American red squirrel (Tamiasciurus hudsonicus) is one of two species of tree squirrel currently classified in the genus Tamiasciurus and known as pine squirrels (the other is the Douglas squirrel, T. douglasii). It is a medium sized (200–250g) diurnal mammal that defends a year-round exclusive territory. The diet of these tree squirrels is specialized on the seeds of conifer cones. As such, they are widely distributed across North America wherever conifers are common, except on the Pacific coasts where they are replaced by Douglas squirrels. Recently red squirrels have been expanding their range to include primarily hardwood areas (Goheen et al. 2003)
North American red squirrels are also referred to as pine squirrels, American red squirrels and chickarees. They should not be confused with Eurasian red squirrels (Sciurus vulgaris); since the ranges of these species do not overlap, they are both commonly referred to as "red squirrels" in the areas where they are native. The species name hudsonicus refers to Hudson Bay, Canada, where the species was first catalogued by Erxleben in 1771 (Woods 1988). Red squirrels can be easily identified from other North American tree squirrels by their smaller size, territorial behavior and reddish fur with a white venter (under-belly; Steele 1998). Red squirrels are also much bigger than chipmunks. The Douglas squirrel is morphologically similar to the American red squirrels but has a rust venter and is restricted to the southwestern coast of British Columbia and in the Pacific Northwest of the United States. These two species do not co-occur.
North American red squirrels are widely distributed across North America. Their range includes most of Canada, and extends into the United States in the Rocky Mountains, the North Central and North East. There are 25 recognized sub-species of red squirrels (Steele 1998). The sub-species of red squirrel found in the southwest Yukon is T. hudsonicus petulans (Osgood, 1900). A recent phylogeny (Mercer and Roth, 2003) suggests that squirrels as a family can be divided into five major lineages. Two of these clades are monotypic. Red squirrels (Tamiasciurus) fall within one of three remaining clades that includes flying squirrels and other tree squirrels (e.g. Sciurus). This clade is thought to have diverged from ground squirrels, chipmunks and marmots. See Mercer and Roth (2003) for details and interesting discussion of the climatic and tectonic events associated with these diversifications.
Western Gray Squirrel
The Western Gray Squirrel (Sciurus griseus) is a tree squirrel found along the western coast of the United States and Canada.
At various times and places, this species has also been known as the Silver-gray Squirrel, the California Gray Squirrel, the Oregon Gray Squirrel, the Columbian Gray Squirrel, the Banner-tail, and also simply as the Gray Squirrel. There are three geographical subspecies: Sciurus griseus griseus (central Washington to the western Sierra Nevada in central California); S. g. nigripes (from south of San Francisco Bay to San Luis Obispo County, California; and S. g. anthonyi, which ranges from San Luis Obispo to south-central California).
The Western Gray Squirrel was first described by George Ord in 1818 based on notes taken by Lewis and Clark at The Dalles in Wasco County, Oregon.
Compared with the Eastern Gray Squirrel S. carolinensis or the Eastern Fox Squirrel (which have been introduced into its range), these squirrels are shy, and will generally run up a tree and give a hoarse barking call when disturbed. Weights vary from about 400 g to nearly 1 kg, and length (including tail) from 45 to 60 cm. It is the largest native tree squirrel in the western coastal United States. Western Gray Squirrels exhibit a form of coloration known as counter shading. The dorsal fur is a silver gunmetal gray, with pure white on the underside; there may be black flecks in the tail. Ears are large but without tufts. The ears turn reddish-brown at the back in the winter. The tail is long and typically very bushy. Tree squirrels undergo a complete head-to-tail molt in the spring and a rump-to-head molt in the fall. Tail hair is replaced only in the spring. Also, nesting mothers will use their tail hair to line birthing nests.
Western Gray Squirrels are forest dwellers, and can be found at elevations up to at least 2000 m. Time on the ground is spent foraging, but they prefer to travel distances from tree to tree. They are strictly diurnal, and feed mainly on seeds and nuts, particularly pine seeds and acorns, though they will also take berries, fungus and other soft food. Pine nuts and acorns are considered critical foods because they are very high in oil and moderately high in carbohydrates, which help increase the development of body fat. They feed mostly in trees and on the ground. They generally forage in the morning and late afternoon for acorns, pine nuts, new tree buds, and fruits. When on alert, they will spread their tails lavishly, creating an umbrella effect that shields them and possibly provides cover from overhead predators. They are scatter-hoarders making numerous caches of food when it is abundant, and thus contribute to the seed dispersion of their food trees. Although they show relatively good scent relocation abilities, some food caches will never be reclaimed, becoming seedlings in the spring. They do not hibernate, but become less active during the winter. Like many prey animals, they depend on auditory alerts from other squirrels or birds to determine safety. Once an alarm call is transmitted, those present will join in, and the trees become a cacophony of barking squirrels. Tree squirrels are prey for bobcats, hawks, eagles, and mountain lions.
Eastern Gray Squirrel
The Eastern Gray Squirrel (Sciurus carolinensis) is a tree squirrel that is native to the Eastern and Midwestern United States, as well as the eastern provinces of Canada. The species name carolinensis refers to the Carolinas, where they were first recorded by zoologists and are still extremely common. The native range of the Eastern Gray Squirrel overlaps with that of the Fox Squirrel (Sciurus niger), with which it is sometimes confused. In Ireland it is known as Iora Glas or Iora Liath.
A prolific and adaptable species, it has been introduced, to and thrives, in several regions of the Western United States. The Eastern Gray Squirrel has also been introduced to Britain where it has successfully spread across the country and displaced the native Red Squirrel (Sciurus vulgaris). It has almost entirely displaced the red squirrel in Ireland also, and there are concerns the same will happen in Italy.
As its name suggests, the Eastern Gray Squirrel's fur is predominantly gray, but it can have a reddish tinge. Its belly is white and it has a large bushy tail. Particularly in urban situations where predation risk is reduced, both albino and melanistic forms of the Eastern Gray Squirrel are quite often found. The melanistic form, which is nearly black all over, is predominant in certain local populations as well as in large parts of southeastern Canada.
Like many members of the family Sciuridae, the Eastern Gray Squirrel is a scatter-hoarder; that is, it hoards food in numerous small caches for recovery later. Some of these caches (especially those made near the site of a sudden abundance of food) are retrieved within hours or days for re-burial in a more secure site. Others are not retrieved until months later. It has been estimated that each squirrel makes several thousand caches each season. The squirrels have very accurate spatial memory for the locations of these caches, and use distant and nearby landmarks to retrieve them. Olfaction is used only once the squirrel is within close range (a few centimeters at most) of the cache site.
These squirrels build a type of nest, known as a drey, in the forks of trees. These consist mainly of dry leaves and twigs. Sometimes they will also attempt to build a nest in the attic or exterior walls of houses, often to the great annoyance and frustration of the homeowner. They also invade bird feeders for millet and sunflower seeds, but safflower is often used instead, as they seem to have no taste for it. Some seed is sold with hot pepper coating, because only mammals such as squirrels can taste its capsaicin, while the birds cannot. Mixing hot pepper flakes into regular birdseed works well as a squirrel deterrent. They have also been known to dig up bulbs from gardens. Their reputation for these habits has led some to call them "tree rats" or "rats with fuzzy tails".
Predators include hunters, hawks, mustelids, skunks, raccoons, domestic cats, snakes and owls. On occasion, this squirrel may lose part of its tail while escaping a predator.