Eastern gray squirrel

Sciurus carolinensis is native to the eastern and midwestern United States, and to the southerly portions of the central provinces of Canada. In the mid-1800s the population in the midwestern United States was described as being "truly astonishing," but human predation and habitat destruction through deforestation resulted in drastic population reductions, to the point that the animal was almost absent from Illinois by 1900. The native range of the eastern gray squirrel overlaps with that of the fox squirrel (Sciurus niger), with which it is sometimes confused, although the core of the fox squirrel's range is slightly more to the west. The eastern gray squirrel is found from New Brunswick, through southwestern Quebec and throughout southern Ontario plus in southern Manitoba, south to East Texas and Florida. A prolific and adaptable species, the eastern gray squirrel has also been introduced to, and thrives in, several regions of the western United States. In 1966, this squirrel was introduced onto Vancouver Island in Western Canada in the area of Metchosin, where it is considered highly invasive and a threat to both the local ecosystem and the native squirrel, the American red squirrel. Overseas, eastern gray squirrels in Europe are a concern because they have displaced some of the native squirrels there. For example, in Britain, they have largely displaced the red squirrel; in Ireland, they compete with the Eurasian red squirrel. They have also been introduced into Italy, South Africa, and Australia (where they were extirpated by 1973). Fossil record S. carolinensis is known to have occurred at least 18 times throughout the North American Pleistocene fossil record, across eight different US states, with some fossils allegedly dating back as early as the late Irvingtonian period. Body size seems to have increased during the early to middle Holocene and then decreased to the present size seen today. This specimen consists of a partial humerus (.172) and two partial tibiae (.173, .174), which are anatomically indistinguishable from that of contemporary S. carolinensis. Surrounding fossil material from the site has been dated back to 18,940–18,530 years ago, during the Late Pleistocene (late Rancholabrean) epoch, and indicates that the site was likely a hardwood-conifer swamp during this time. ==Etymology==

The generic name, Sciurus, is derived from two Greek words, skia 'shadow' and oura 'tail'. This name alludes to the squirrel sitting in the shadow of its tail. The specific epithet, carolinensis, refers to the Carolinas, where the species was first recorded and where the animal is still extremely common. In the United Kingdom and Canada, it is simply referred to as the "grey squirrel". In the US, "eastern" is used to differentiate the species from the western gray squirrel (Sciurus griseus). ==Characteristics==

The eastern gray squirrel has predominantly gray fur with brown spots and streaks. It has a white underside as compared to the brownish-orange underside of the fox squirrel; both exhibit countershading. It has a large bushy tail. Particularly in urban situations where the risk of predation is reduced, both white-colored and black-colored individuals are quite often found. The melanistic form, which is almost entirely black, is predominant in certain populations and in certain geographic areas, such as in large parts of southeastern Canada. Melanistic squirrels appear to exhibit a higher cold tolerance than the common gray morph; when exposed to −10 °C, black squirrels showed an 18% reduction in heat loss, a 20% reduction in basal metabolic rate, and an 11% increase to non-shivering thermogenesis capacity when compared to the common gray morph. The head and body length is from , the tail from , and the adult weight varies between . They do not display sexual dimorphism, meaning there is no gender difference in size or coloration. The tracks of an eastern gray squirrel are difficult to distinguish from the related fox squirrel and Abert's squirrel, though the latter's range is almost entirely different from the gray's. Like all squirrels, the eastern gray shows four toes on the front feet and five on the hind feet. The hind foot-pad is often not visible in the track. When bounding or moving at speed, the front foot tracks will be behind the hind foot tracks. The bounding stride can be long. The dental formula of the eastern gray squirrel is 1023/1013 (upper teeth/lower teeth). or pups. They weigh at birth. They are born blind, entirely hairless, and pink with whiskers present at birth. 7–10 days postpartum, the skin begins to darken, just before the juvenile pelage grows in. Lower incisors erupt 19–21 days postpartum, while upper incisors erupt after 4 weeks. Cheek teeth erupt during week 6. Eyes open after 21–42 days, and ears open 3–4 weeks postpartum. Weaning is initiated around 7 weeks postpartum, and is usually finished by week 10, followed by the loss of the juvenile pelage. Full adult body mass is achieved by 8–9 months after birth. A frequent illness spread by ticks is Lyme disease. Ticks can also spread Rocky Mountain spotted fever. It can result in damage to internal organs including the heart and kidney if not properly treated. An eastern gray squirrel is susceptible to diseases including fibromatosis and squirrelpox. A squirrel with fibromatosis, a virus-induced illness, may grow massive skin tumors all over the body. Blindness could result from a tumor that is located close to a squirrel's eye. == Behavior and ecology ==

Like many members of the family Sciuridae, the eastern gray squirrel is a scatter-hoarder; it hoards food in numerous small caches for later recovery. Squirrels sometimes use deceptive behavior to prevent other animals from retrieving cached food. For example, they will pretend to bury the object if they feel that they are being watched. They do this by preparing the spot as usual, for instance, digging a hole or widening a crack, miming the placement of the food, while actually concealing it in their mouths, and then covering up the "cache" as if they had deposited the object. They also hide behind vegetation while burying food or hide it high up in trees (if their rival is not arboreal). Such a complex repertoire suggests that the behaviours are not innate, and imply theory of mind thinking. The eastern gray squirrel is one of very few mammalian species that can descend a tree head-first. It does this by turning its feet so the claws of its hind paws are backward-pointing and can grip the tree bark. Eastern gray squirrels build a type of nest, known as a drey, in the forks of trees, consisting mainly of dry leaves and twigs. The dreys are roughly spherical, about 30 to 60 cm in diameter and are usually insulated with moss, thistledown, dried grass, and feathers to reduce heat loss. In addition, squirrels may inhabit a permanent tree den hollowed out in the trunk or a large branch of a tree. Reproduction Eastern gray squirrels can breed twice a year, but younger and less experienced mothers normally have a single litter per year in the spring. Depending on forage availability, older and more experienced females may breed again in summer. In a year of abundant food, 36% of females bear two litters, but none will do so in a year of poor food. Their breeding seasons are December to February and May to June, though this is slightly delayed in more northern latitudes. but females are not normally fertile until at least one year of age. Their mean age of first estrus is 1.25 years. Reproductive longevity for females appears to be over 8 years, with 12.5 years documented in North Carolina. The use of vocal and visual communication has been shown to vary by location, based on elements such as noise pollution and the amount of open space. For instance, populations living in large cities generally rely more on the visual signals, due to the generally louder environment with more areas without much visual restriction. However, in heavily wooded areas, vocal signals are used more often due to the relatively lower noise levels and a dense canopy restricting visual range. Habitat In the wild, eastern gray squirrels can be found inhabiting large areas of mature, dense woodland ecosystems, generally covering 100 acres (40 hectares) of land. Eastern gray squirrels also use dens for protection from predators and to help them look after their young. Young survive 40 percent less if they lived in a leaf nest compared to a den. Squirrels tend to claim 2-3 dens at the same time. Canopy and midstory trees are used by squirrels to hide from predators such as hawks and owls. The typical squirrel ranges over and tends to be smaller where more of them are found. Ecosystem Eastern gray squirrels forage tree seeds and disperse them through seed-caching. They may also contribute to the distribution of truffle fungal spores when they eat truffles. They are an important prey source and parasitic host for other animals. Predation Eastern gray squirrels predators include hawks, weasels, raccoons, bobcats, foxes, domestic and feral cats, snakes, owls, and dogs. Raccoons and weasels may consume a squirrel depending on where it lives in the United States. Rattlesnakes eat squirrels in California as they are searching for food in a heavy forest. When a predator is approaching the eastern gray squirrel, other squirrels will inform the squirrel of the predator by sending an acoustic signal to let the squirrel know. The speed of a squirrel makes it hard for it to be captured by the predators. == Diet ==

Eastern gray squirrels eat a range of foods, such as many types of seeds and nuts, including acorns, walnuts, and hazelnuts, tree buds, flowers, berries, tree bark, and some types of forest fungi, including fly agaric mushrooms including other squirrels. Eastern tree squirrels can cause damage to trees by tearing the bark and eating the soft cambial tissue underneath. In Europe, sycamore and beech suffer the greatest damage. Mast-bearing gymnosperms such as cedar, hemlock, pine, and spruce are another food source, Tree squirrels also raid gardens for wheat, Sometimes they eat the tomato seeds and discard the rest. On occasion, eastern gray squirrels also prey upon insects, frogs, small rodents including other squirrels, and small birds, their eggs, and young. In urban and suburban areas, these squirrels scavenge for food in trash bins. However, these foods are not safe for them to digest because they include sugar, fat, as well as additives that can make them sick. Eastern gray squirrels are sometimes mistakenly thought to be herbivores, but they are omnivores. Eastern gray squirrels have a high enough tolerance for humans to inhabit residential neighborhoods and raid bird feeders for millet, corn, and sunflower seeds. Some people who feed and watch birds for entertainment also intentionally feed seeds and nuts to squirrels for the same reason. However, in the UK eastern gray squirrels can take a significant proportion of supplementary food from feeders, preventing access and reducing use by wild birds. Attraction to supplementary feeders can increase local bird nest predation, as eastern gray squirrels are more likely to forage near feeders, resulting in increased likelihood of finding nests, eggs and nestlings of small passerines. == Introductions and impact ==

in the UK (Bunhill Fields, London) The eastern gray squirrel is an introduced species in a variety of locations in western North America: in western Canada, to the southwest corner of British Columbia and to the city of Calgary, Alberta; In South Africa, though exotic, it is not usually considered an invasive species owing to its small range (only found in the extreme southwestern part of the Western Cape, going north as far as the small farming town of Franschhoek), as well because it inhabits urban areas and places greatly affected by humans, such as agricultural areas and exotic pine plantations. Here, it mostly eats acorns and pine seeds, although it will take indigenous and commercial fruit, as well. Even so, it is unable to use the natural vegetation (fynbos) found in the area, a factor which has helped to limit its spread. It does not come into contact with native squirrels due to geographic isolation (a native tree squirrel, Paraxerus cepapi, is found only in the savanna regions in the northeast of the country) and different habitats. Gray squirrels were first introduced to Britain in the 1870s, as fashionable additions to estates. In 1921 it was reported in The Times that the Zoological Society of London had released eastern greys to breed at liberty in Regents Park: They spread rapidly across England, and then became established in both Wales and parts of southern Scotland. On mainland Britain, they have almost entirely displaced native red squirrels. Larger than red squirrels and capable of storing up to four times more fat, gray squirrels are better able to survive winter conditions. They produce more young and can live at higher densities. Gray squirrels also carry the squirrelpox virus, to which red squirrels have no immunity. When an infected gray squirrel introduces squirrelpox to a red squirrel population, its decline is 17–25 times greater than through competition alone. However, physicians in the United States have warned that squirrel brains should not be eaten, because of the risk that they may carry Creutzfeldt–Jakob disease. As an invasive species eating seeds In many locations in North America and Europe, the grey squirrel is considered an invasive species and has displaced native red squirrel populations. Red squirrel displacement is notable in Britain, Ireland, Italy, and on Vancouver Island. The main factor in the eastern gray squirrel's displacement of the red squirrel is thought to be its greater fitness, hence a competitive advantage over the red squirrel Within 15 years of the grey squirrel's introduction to a red squirrel habitat in Great Britain, red squirrel populations are extinct. The eastern gray squirrel tends to be larger and stronger than the red squirrel and has been shown to have a greater ability to store fat for winter. Due to the dearth of trees in their native Ireland for them to reside in, red squirrels are the only species being harmed by the invasion of grey squirrels. other than the European pine marten, which is generally absent from England and Wales. This has aided its rapid population growth and has led to the species being classed as a pest and it is now illegal to release captured eastern grey squirrels back into the wild in the UK. Measures are being devised to reduce its numbers, including a campaign starting in 2006 named "Save Our Squirrels" using the slogan "Save a red, eat a grey!" which attempted to re-introduce squirrel meat in to the local market, with celebrity chefs promoting the idea, cookbooks introducing recipes containing squirrel and the Forestry Commission providing a regular supply of squirrel meat to British restaurants, factories and butchers. In areas where relict populations of red squirrels survive, such as the islands of Anglesey, Brownsea and the Isle of Wight, programs exist to eradicate gray squirrels and prevent them from reaching these areas in order to allow red squirrel populations to recover and grow. ==See also==