Eastern Gray Squirrel
Overview
 
The eastern gray squirrel (Sciurus carolinensis) is a tree squirrel
Tree squirrel
Tree squirrels include over a hundred species that are found on all continents except Antarctica, and are the members of the squirrel family most commonly referred to as "squirrels"...

 in the genus Sciurus
Sciurus
The genus Sciurus contains most of the common, bushy-tailed squirrels in North America, Europe, temperate Asia, Central America and South America.-Species:There are 30 species.Genus Sciurus - Tree squirrels*Subgenus Sciurus...

native to the eastern
Eastern United States
The Eastern United States, the American East, or simply the East is traditionally defined as the states east of the Mississippi River. The first two tiers of states west of the Mississippi have traditionally been considered part of the West, but can be included in the East today; usually in...

 and midwestern United States
Midwestern United States
The Midwestern United States is one of the four U.S. geographic regions defined by the United States Census Bureau, providing an official definition of the American Midwest....

, and to the southerly portions of the eastern provinces of Canada. The native range of the eastern gray squirrel overlaps with that of the fox squirrel
Fox Squirrel
The fox squirrel is the largest species of tree squirrel native to North America...

 (Sciurus niger), with which it is sometimes confused, although the core of the fox squirrel's range is slightly more to the west.

A prolific and adaptable species, the eastern gray squirrel has been introduced to, and thrives, in several regions of the western United States
Western United States
.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...

.
Encyclopedia
The eastern gray squirrel (Sciurus carolinensis) is a tree squirrel
Tree squirrel
Tree squirrels include over a hundred species that are found on all continents except Antarctica, and are the members of the squirrel family most commonly referred to as "squirrels"...

 in the genus Sciurus
Sciurus
The genus Sciurus contains most of the common, bushy-tailed squirrels in North America, Europe, temperate Asia, Central America and South America.-Species:There are 30 species.Genus Sciurus - Tree squirrels*Subgenus Sciurus...

native to the eastern
Eastern United States
The Eastern United States, the American East, or simply the East is traditionally defined as the states east of the Mississippi River. The first two tiers of states west of the Mississippi have traditionally been considered part of the West, but can be included in the East today; usually in...

 and midwestern United States
Midwestern United States
The Midwestern United States is one of the four U.S. geographic regions defined by the United States Census Bureau, providing an official definition of the American Midwest....

, and to the southerly portions of the eastern provinces of Canada. The native range of the eastern gray squirrel overlaps with that of the fox squirrel
Fox Squirrel
The fox squirrel is the largest species of tree squirrel native to North America...

 (Sciurus niger), with which it is sometimes confused, although the core of the fox squirrel's range is slightly more to the west.

A prolific and adaptable species, the eastern gray squirrel has been introduced to, and thrives, in several regions of the western United States
Western United States
.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...

. It has also been introduced to Britain, where it has spread across the country and has largely displaced the native red squirrel
Red Squirrel
The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia...

, Sciurus vulgaris. In Ireland, the red squirrel has been displaced in several eastern counties, though it still remains common in the south and west of the country. There are concerns that such displacement might happen in Italy and that gray squirrels might spread from Italy to other parts of mainland Europe.

Etymology

The genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, Sciurus, is derived from two Greek words, skia, meaning shadow, and oura, meaning tail. This name alludes to the squirrel sitting in the shadow of its tail. The specific epithet, carolinensis, refers to the Carolinas
The Carolinas
The Carolinas is a term used in the United States to refer collectively to the states of North and South Carolina. Together, the two states + have a population of 13,942,126. "Carolina" would be the fifth most populous state behind California, Texas, New York, and Florida...

, 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".

Description

As the name suggests, the eastern gray squirrel has predominantly gray fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...

 but it can have a brownish color. It has a white underside and a large bushy tail. Particularly in urban situations where the risk of predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

 is reduced, both white
Albinism
Albinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin...

- and black
Melanism
Melanism is an undue development of dark-colored pigment in the skin or its appendages, and the opposite of albinism. It is also the medical term for black jaundice.The word is deduced from the , meaning black pigment....

-colored individuals are quite often found. The melanistic form
Black squirrel
The black squirrel is a melanistic subgroup of the Eastern Grey Squirrel. They are common in the Midwestern United States, Ontario, Quebec, and in parts of the Northeastern United States and Britain.-Habitat:...

, which is almost entirely black, is predominant in certain populations and in certain geographic areas, such as in large parts of southeastern Canada. There are also genetic variations within these, including individuals with black tails and black colored squirrels with white tails. The head and body length is from 23 to 30 cm (9.1 to 11.8 in), the tail from 19 to 25 cm (7.5 to 9.8 in) and the adult weight varies between 400 and 600 g (14.1 and 21.2 oz).
The tracks of an eastern gray squirrel are difficult to distinguish from its cousins the fox squirrel
Fox Squirrel
The fox squirrel is the largest species of tree squirrel native to North America...

 and Abert's squirrel
Abert's Squirrel
Abert's squirrel is a tree squirrel in the genus Sciurus endemic to the Rocky Mountains from United States to Mexico, with concentrations found in Arizona, The Grand Canyon, New Mexico, and southwestern Colorado.-Etymology:The Abert's squirrel is named after Colonel John James Abert, an American...

, though the latter's range is almost entirely different from the gray's. Like all squirrels, the eastern gray shows four fingers 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 two or three feet long.

Behavior

Like many members of the family Sciuridae, the eastern gray squirrel is a scatter-hoarder
Scatter-hoarder
Hoarding or caching is a type of animal behavior where an animal will store its food in times of surplus for times when food is less plentiful...

; it hoards food in numerous small caches for later recovery. Some caches are quite temporary, especially those made near the site of a sudden abundance of food which can be retrieved within hours or days for re-burial in a more secure site. Others are more permanent and 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
Spatial memory
In cognitive psychology and neuroscience, spatial memory is the part of memory responsible for recording information about one's environment and its spatial orientation. For example, a person's spatial memory is required in order to navigate around a familiar city, just as a rat's spatial memory is...

 for the locations of these caches, and use distant and nearby landmarks to retrieve them. Smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...

 is used once the squirrel is within a few centimeters of the cache. It is one of very few mammalian species that can descend a tree head-first. It does this by turning its feet so that the claws of its hindpaws are backward pointing and can grip the tree bark.

Eastern gray squirrels build a type of nest
Nest
A nest is a place of refuge to hold an animal's eggs or provide a place to live or raise offspring. They are usually made of some organic material such as twigs, grass, and leaves; or may simply be a depression in the ground, or a hole in a tree, rock or building...

, known as a drey, in the forks of trees. The drey consists mainly of dry leaves and twigs. Squirrels may also nest in the attic
Attic
An attic is a space found directly below the pitched roof of a house or other building . Attic is generally the American/Canadian reference to it...

 or exterior walls of a house. In addition, the squirrel may inhabit a permanent tree den.

Eastern gray squirrels are more active during the early and late hours of the day, and tend to avoid the heat in the middle of a summer day. They do not hibernate.

Predators include humans
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...

, hawks
Accipitridae
The Accipitridae, one of the two major families within the order Accipitriformes , are a family of small to large birds with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a...

, weasels
Mustelidae
Mustelidae , commonly referred to as the weasel family, are a family of carnivorous mammals. Mustelids are diverse and the largest family in the order Carnivora, at least partly because in the past it has been a catch-all category for many early or poorly differentiated taxa...

, raccoon
Raccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...

s, domestic
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

 and feral cat
Feral cat
A feral cat is a descendant of a domesticated cat that has returned to the wild. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats are born in the wild; the offspring of a stray cat can be considered feral if born in the wild.In many parts of...

s, snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s, owl
Owl
Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...

s and dogs. Whilst gray squirrels fight among themselves over food sources, they have been known to mob potential predators such as domestic cats. They also have a complex, tag-team defensive system involving distracting would-be predators with vigorous shaking of their tails.

Reproduction

Eastern gray squirrels breed twice a year, December to February and May to June, though this is slightly delayed in more northern latitudes. The first litter is born in February to March, the second in June to July. There are normally two to six young in each litter, but this number can be as high as 8. The gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 period is about 44 days. The young are weaned
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...

 at 7 weeks and leave the nest after 10 weeks.

Eastern gray squirrels can start breeding as early as 5 and a half months old, but usually breed for the first time at a year old. It can live to be 20 years old in captivity, but in the wild it usually only lives to a maximum of 12.5 years old.

Communication

As in most other mammals, communication among eastern gray squirrel individuals involves both vocalizations and posturing. It has a quite varied repertoire of vocalizations, including a squeak similar to that of a mouse, a low pitched noise, a chatter, and a raspy "mehr mehr mehr". Other methods of communication include tail-flicking. Communications are mainly used in mating season and to ward off predators.

Diet

Eastern gray squirrels eat a range of foods such as tree bark, many types of seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s and acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

s, walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

s, and other nuts
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

, and some types of fungi found in the forests, including fly agaric mushrooms (Amanita muscaria
Amanita muscaria
Amanita muscaria, commonly known as the fly agaric or fly amanita , is a poisonous and psychoactive basidiomycete fungus, one of many in the genus Amanita...

).

Eastern gray squirrels have a high enough tolerance for humans to inhabit residential neighborhoods and will raid bird feeders for millet
Millet
The millets are a group of small-seeded species of cereal crops or grains, widely grown around the world for food and fodder. They do not form a taxonomic group, but rather a functional or agronomic one. Their essential similarities are that they are small-seeded grasses grown in difficult...

, corn, and sunflower seed
Sunflower seed
The sunflower seed is the fruit of the sunflower . The term "sunflower seed" is actually a misnomer when applied to the seed in its pericarp . Botanically speaking, it is more properly referred to as an achene. When dehulled, the edible remainder is called the sunflower kernel.There are three types...

s. On very rare occasions, when its usual food source is scarce, eastern gray squirrels will also prey upon insects, frogs, small rodents, including other squirrels, and small birds, their eggs and young. They will also gnaw on bones, antlers, and turtle shells – likely as a source of minerals sparse in their normal diet.

Habitat

In the wild, eastern gray squirrels can be found inhabiting large areas of mature, dense woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...

 ecosystems, that generally cover 40 hectares of land. These forests usually contain large amounts of dense vegetation that provides sufficient amount of food sources and favorable shelters for eastern gray squirrels. Eastern gray squirrels generally prefer constructing their dens upon large tree branches and within the hollow trunks of trees. They also have been known to take shelter within abandoned bird nests. The dens are usually lined with moss plants, thistledown, dried grass, and feathers. These perhaps provide and assist in the insulation of the den, used to reduce heat loss. A cover to the den is usually built afterwards. Close to human settlements, eastern gray squirrels are found in parks and backyards of houses within urban environments and in the farmlands of rural environments.

Distribution

The eastern gray squirrel is found in the eastern United States and adjacent southern Canada; New Brunswick to Manitoba, south to eastern Texas and Florida. It has also been introduced into Ireland and Britain, Italy, South Africa, and also Australia (where it was extirpated
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...

 by 1973).

Introductions

The eastern gray squirrel has been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

 to a variety of locations in western North America: in Canada, to the southwest corner of British Columbia and to the city of Calgary, Alberta; in the United States, to the states of Washington and Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

 and, in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, to the city of San Francisco
San Francisco, California
San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...

 and the peninsula area of San Mateo
San Mateo County, California
San Mateo County is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and...

 and Santa Clara
Santa Clara County, California
Santa Clara County is a county located at the southern end of the San Francisco Bay Area in the U.S. state of California. As of 2010 it had a population of 1,781,642. The county seat is San Jose. The highly urbanized Santa Clara Valley within Santa Clara County is also known as Silicon Valley...

 counties, south of the city. It has become the most common squirrel in many urban and suburban habitats in western North America, from north of central California to southwest British Columbia. At the turn of the 19th to 20th century the eastern gray squirrel was introduced into South Africa, Ireland and England.

In South Africa, though exotic, it is not usually considered an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 owing to its small range (only found in the extreme southwestern part of the Western Cape, going up as far as the small farming town of Franschoek) as well as the fact that 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 utilize the natural vegetation (fynbos
Fynbos
Fynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...

) 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 north-east of the country) and different habitats.

It spread rapidly across England and then became established in both Wales and parts of southern Scotland. On mainland Britain, it has almost entirely displaced the populations of native red squirrels. On the island of Ireland, this displacement has not been as rapid, owing to the fact there was only a single introduction, in County Longford
County Longford
County Longford is a county in Ireland. It is part of the Midlands Region and is also located in the province of Leinster. It is named after the town of Longford.Longford County Council is the local authority for the county...

. Schemes have been introduced to control the population in Ireland in order to encourage the native red squirrels. Eastern gray squirrels have also been introduced to Italy, and the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 has expressed concern that it will similarly displace the red squirrel from parts of the European continent.

Displacement of red squirrels

In the United Kingdom and in Ireland, the eastern gray squirrel has few natural predators. This has aided its rapid population growth and has led to the species being classed as a pest. Measures are being devised to reduce its numbers, including one plan for celebrity television chefs to promote the idea of eating the squirrels. In areas where relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....

 populations of red squirrel
Red Squirrel
The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia...

 survive, such as the islands of Anglesey
Anglesey
Anglesey , also known by its Welsh name Ynys Môn , is an island and, as Isle of Anglesey, a county off the north west coast of Wales...

 and Brownsea, programs seeking to eradicate pest squirrels are in progress in an effort to allow red squirrel populations to recover.
Although complex and controversial, the main factor in the eastern gray squirrel's displacement of the red squirrel is thought to be its greater fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

 and, hence, a competitive advantage over the red squirrel on all measures. 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
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

 for winter. The squirrel can therefore compete more effectively for a larger share of the available food, resulting in relatively lower survival and breeding rates among the red squirrel. Parapoxvirus
Parapoxvirus
Parapoxviruses belong to the Poxviridae family. Like all members of that family, they are oval, relatively large, double-stranded DNA viruses. Parapoxviruses have a unique spiral coat that distinguishes them from other poxviruses. Parapoxviruses infect vertebrates.Not all parapoxviruses are...

 may also be a strongly contributing factor; red squirrels are fatally affected by the disease, while the eastern gray squirrels are unaffected but thought to be carriers. The red squirrel is also less tolerant of habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

 and fragmentation which has led to its population decline, while the more adaptable eastern gray squirrel has taken advantage and expanded.

Similar factors appear to have been at play in the Pacific region of North America, where the native American red squirrel
American Red Squirrel
The American Red Squirrel is one of three species of tree squirrel currently classified in the genus Tamiasciurus and known as pine squirrels...

 has been largely displaced by the eastern gray squirrel in parks and forests throughout much of the region.

Ironically, 2008 saw the rise of "fears" for the future of the eastern gray squirrel, as the melanistic form (black) began to spread through the southern British population. In the UK, if a "grey squirrel" (eastern gray squirrel) is trapped, under the Wildlife and Countryside Act 1981
Wildlife and Countryside Act 1981
The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom and was implemented to comply with the Directive 2009/147/EC on the conservation of wild birds...

 it is illegal to release it or to allow it to escape into the wild; instead they should be humanely destroyed.

External links

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