The eastern gray squirrel (''Sciurus carolinensis''), also known, particularly outside of North America, as simply the grey squirrel, is a
tree squirrel in the genus ''
Sciurus''. It is native to eastern North America, where it is the most prodigious and ecologically essential natural forest regenerator. Widely introduced to certain places around the world,
the eastern gray squirrel in Europe, in particular, is regarded as an
invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
.
In Europe, ''Sciurus carolinensis'' is included since 2016 in the
list of Invasive Alien Species of Union concern (the Union list). This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.
Distribution
''Sciurus carolinensis'' is native to the
eastern and
midwestern United States, and to the southerly portions of the central provinces of
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
. 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.
Breeding eastern gray squirrels are found in Nova Scotia, but whether this population was introduced or came from natural range expansion is not known.
A prolific and adaptable species, the eastern gray squirrel has also been introduced to, and thrives in, several regions of the
western United States and in 1966, this squirrel was introduced into Vancouver Island in Western Canada in the area of Metchosin, and has spread widely from there. They are considered highly invasive and a threat to both the local ecosystem and the native squirrel, the
American red squirrel
The American red squirrel (''Tamiasciurus hudsonicus'') is one of three species of tree squirrels currently classified in the genus ''Tamiasciurus'', known as the pine squirrels (the others are the Douglas squirrel, ''T. douglasii'', and the sou ...
.
Overseas,
Eastern gray squirrels in Europe
Europe's grey squirrels (''Sciurus carolinensis'') originated in North America, where they are known as eastern gray squirrelsBertolino, S. & Piero, G. (2003) Spread and attempted eradication of the grey squirrel (Sciurus caolinensis) in Italy ...
are a concern because they have displaced some of the native squirrels there. They have been introduced into Ireland, Britain, Italy, South Africa, and Australia (where it was
extirpated by 1973).
In Ireland, the native squirrel – also colored red – the
Eurasian red squirrel
The red squirrel (''Sciurus vulgaris'') is a species of tree squirrel in the genus ''Sciurus'' common throughout Europe and Asia. The red squirrel is an arboreal, primarily herbivorous rodent.
In Great Britain, Ireland, and in Italy numbers ...
''S. vulgaris'' – has been displaced in several eastern counties, though it still remains common in the south and west of the country. The gray squirrel is also an
invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
in Britain; it has spread across the country and has largely displaced the red squirrel. That such a displacement might happen in Italy is of concern, as gray squirrels might spread to other parts of
mainland Europe.
Etymology
The
generic name, ''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
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
, ''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'').
Description
The eastern gray squirrel has predominantly gray
fur, but it can have a brownish color. It has a usual white underside as compared to the typical brownish-orange underside of the fox squirrel. It has a large bushy tail. Particularly in urban situations where the risk of
predation is reduced, both white – 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 black coloration is caused by an incomplete dominant mutation of MC1R, where ''E+/E+'' is a wild type squirrel, ''E+/EB'' is brown-black, and ''EB/EB'' is black.]
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 two to three feet long.
The dental formula of the eastern gray squirrel is 1023/1013 (upper teeth/lower teeth).[
× 2 = 22 total teeth.
Incisors exhibit indeterminate growth, meaning they grow consistently throughout life, and their cheek teeth exhibit brachydont (low-crowned teeth) and bunodont (having tubercles on crowns) structures.][
]
Behavior
Like many members of the family Sciuridae, the eastern gray squirrel is a scatter-hoarder
Hoarding or caching in animal behavior is the storage of food in locations hidden from the sight of both conspecifics (animals of the same or closely related species) and members of other species. Most commonly, the function of hoarding or cachi ...
; 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 reburial in a more secure site. Others are more permanent and are not retrieved until months later. Each squirrel is estimated to make several thousand caches each season. The squirrels have very accurate spatial memory
In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Sp ...
for the locations of these caches, and use distant and nearby landmarks to retrieve them. Smell
Smell may refer to;
* Odor, airborne molecules perceived as a scent or aroma
* Sense of smell, the scent also known scientifically as olfaction
* "Smells" (''Bottom''), an episode of ''Bottom''
* The Smell, a music venue in Los Angeles, Californ ...
is used partly to uncover food caches, and also to find food in other squirrels' caches. Scent can be unreliable when the ground is too dry or covered in snow.
Squirrels sometimes use deceptive behavior to prevent other animals from retrieving cached food. 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 behaviors 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. Males and females may share the same nest for short times during the breeding season, and during cold winter spells. Squirrels may share a drey to stay warm. They may also nest in the attic
An attic (sometimes referred to as a '' loft'') is a space found directly below the pitched roof of a house or other building; an attic may also be called a ''sky parlor'' or a garret. Because attics fill the space between the ceiling of the ...
or exterior walls of a house, where they may be regarded as pests, as well as fire hazards due to their habit of gnawing on electrical cables. In addition, squirrels may inhabit a permanent tree den hollowed out in the trunk or a large branch of a tree.
Eastern gray squirrels are crepuscular
In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylig ...
, or 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
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
.
Squirrels are creatures that bite people and rob them of their food. They can attack people by biting their hands. Squirrels can dwell in attics or on rooftops by creating nests. Prior to burying an acorn, a squirrel actually shovels its face inside of it, making it easier to find afterwards. Squirrels gnaw on items to postpone the appearance of their front teeth. To prevent the lower jaw and cranium from developing into their front teeth once they start to emerge, they gnaw on objects that wear down their teeth.
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. The first litter is born in February or March, the second in June or July, though, again, bearing may be advanced or delayed by a few weeks depending on climate, temperature, and forage availability. In any given breeding season, an average of 61 – 66% of females bear young. If a female fails to conceive or loses her young to unusually cold weather or predation, she re-enters estrus and has a later litter. Five days before a female enters estrus, she may attract up to 34 males from up to 500 meters away. Eastern gray squirrels exhibit a form of polygyny, in which the competing males will form a hierarchy of dominance, and the female will mate with multiple males depending on the hierarchy established.[
Normally, one to four young are born in each litter, but the largest possible litter size is eight.] The gestation
Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
period is about 44 days. The young are weaned around 10 weeks, though some may wean up to six weeks later in the wild. They begin to leave the nest after 12 weeks, with autumn born young often wintering with their mother. Only one in four squirrel kits survives to one year of age, with mortality around 55% for the following year. Mortality rates then decrease to around 30% for following years until they increase sharply at eight years of age.
Rarely, eastern gray females can enter estrus as early as five and a half months old, but females are not normally fertile until at least one year of age. Their mean age of first estrus is 1.25 years. The presence of a fertile male will induce ovulation in a female going through estrus.[ Male eastern grays are sexually mature between one and two years of age. Reproductive longevity for females appears to be over 8 years, with 12.5 years documented in North Carolina.][ These squirrels can live to be 20 years old in captivity, but in the wild live much shorter lives due to predation and the challenges of their habitat. At birth, their life expectancy is 1–2 years, an adult typically can live to be six, with exceptional individuals making it to 12 years.
]
Growth and ontogeny
Newborn gray squirrels weigh 13–18 grams and are entirely hairless and pink, although vibrissae
Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarse ...
are 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.[
]
Communication
As in most other mammals, communication among eastern gray squirrel individuals involves both vocalizations and posturing. The species 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 and other gestures, including facial expressions. Tail flicking and the "kuk" or "quaa" call are used to ward off and warn other squirrels about predators, as well as to announce when a predator is leaving the area. Squirrels also make an affectionate coo-purring sound that biologists call the "muk-muk" sound. This is used as a contact sound between a mother and her kits and in adulthood, by the male when he courts the female during mating season.
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.
Diet
Eastern gray squirrels eat a range of foods, such as tree bark, tree buds, flowers, berries, many types of seeds and acorn
The acorn, or oaknut, is the nut of the oaks and their close relatives (genera ''Quercus'' and '' Lithocarpus'', in the family Fagaceae). It usually contains one seed (occasionally
two seeds), enclosed in a tough, leathery shell, and borne ...
s, walnuts, and other nuts
Nut often refers to:
* Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds
* Nut (hardware), fastener used with a bolt
Nut or Nuts may also refer to:
Arts, entertainment, and media Com ...
, like hazelnuts (see picture) and some types of fungi found in the forests, including fly agaric mushrooms (''Amanita muscaria
''Amanita muscaria'', commonly known as the fly agaric or fly amanita, is a basidiomycete of the genus ''Amanita''. It is also a muscimol mushroom. Native throughout the temperate and boreal regions of the Northern Hemisphere, ''Amanita muscar ...
''). They can cause damage to trees by tearing the bark and eating the soft cambial tissue underneath. In Europe, sycamore (''Acer pseudoplatanus
''Acer pseudoplatanus'', known as the sycamore in the British Isles and as the sycamore maple in the United States, is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is a large deciduous, broad-leaved tree, tol ...
'' L.) and beech ('' Fagus sylvatica'' L.) suffer the greatest damage. The seeds and catkins of gymnosperms cedar, hemlock, pine, and spruce
A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ...
are another food source, as well as those of angiosperms such as hickory
Hickory is a common name for trees composing the genus ''Carya'', which includes around 18 species. Five or six species are native to China, Indochina, and India (Assam), as many as twelve are native to the United States, four are found in Mexi ...
, oak, and walnut, and truffles. Mast-Bearing Hardwood Trees are also very important to their diet. These trees help store food like Acorns, Beechnuts, and Hickory Nuts, which are important foods for them during the Spring and Fall months. Red Oak Acorns are found in the Spring, Winter and Fall. White Oak Acorns are found in the Fall and Winter. Hickory and Beechnuts are found in Spring, Winter and Fall. Walnuts are found in Fall and Winter. Buds and flowers are found in Spring and Summer. Fleshy fruits and berries are found in Summer. Fungi Mushrooms are found in Spring, Summer, and Fall. Yellow Popular Seeds are found in Summer, Fall and Winter. The squirrels also raid gardens for wheat, tomatoes, corn
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
, strawberries
The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...
, and other garden crops. Sometimes they eat the tomato seeds and discard the rest. On occasion, eastern gray squirrels also prey upon insects
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...
, frogs
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...
, small rodents including other squirrels, and small birds, their eggs, and young. They also gnaw on bones, antler
Antlers are extensions of an animal's skull found in members of the Cervidae (deer) family. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally found only on ...
s, and turtle shells – likely as a source of minerals scarce in their normal diet. In urban and suburban areas, these squirrels scavenge for food in trash bins. However, these foods aren't safe for them to digest because they include sugar, fat, as well as additives that can make them sick. Eastern gray squirrels are 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 feeder
A birdfeeder, bird table, or tray feeder are devices placed outdoors to supply bird food to birds ( bird feeding). The success of a bird feeder in attracting birds depends upon its placement and the kinds of foods offered, as different species ...
s for millet
Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets ...
, corn, and sunflower seed
The sunflower seed is the seed of the sunflower (''Helianthus annuus''). There are three types of commonly used sunflower seeds: linoleic (most common), high oleic, and sunflower oil seeds. Each variety has its own unique levels of monounsatu ...
s. Some people who feed and watch birds for entertainment also intentionally feed seeds and nuts to the 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.
Predation
Eastern gray squirrels predators include hawks
Hawks are birds of prey of the family Accipitridae. They are widely distributed and are found on all continents except Antarctica.
* The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks and others. This subfa ...
, weasels, raccoon
The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight o ...
s, bobcat
The bobcat (''Lynx rufus''), also known as the red lynx, is a medium-sized cat native to North America. It ranges from southern Canada through most of the contiguous United States to Oaxaca in Mexico. It is listed as Least Concern on the IU ...
s, fox
Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush'').
Twelv ...
es, domestic and feral cat
A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact: it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...
s, snake
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...
s, owls, and dogs. Their primary predators are hawks, owls, and snakes. 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. The squirrel is susceptible to be eaten by a fox in the eastern region of the United States.
In its introduced range in South Africa, it has been preyed on by African harrier-hawks. When a predator is approaching the Eastern Gray Squirrel, other squirrels will inform the squirrel of the predator by sending a signal to let the squirrel know. The speed of a squirrel makes it hard for it to be captured by the predators.
Diseases
Diseases like Typhus
Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...
, Plague
Plague or The Plague may refer to:
Agriculture, fauna, and medicine
*Plague (disease), a disease caused by ''Yersinia pestis''
* An epidemic of infectious disease (medical or agricultural)
* A pandemic caused by such a disease
* A swarm of pes ...
, and Tularemia are spread by Eastern Gray Squirrels. If not properly treated, these diseases have the potential to kill squirrels. When bitten or exposed to bodily fluids, humans can contract these diseases. Also carried by Eastern Grey Squirrels are parasites like ringworm, fleas, lice, mites, and ticks. Eastern Grey Squirrels also die from these parasites. Their skin may become rough, blotchy, and prone to hair loss due to the mite parasite during the chilly winter months. The parasites aren't transferred to people when these squirrels reside in attics or homes. A frequent illness spread by ticks is Lyme disease
Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...
. 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 illness. They are susceptible to diseases including fibromatosis and squirrel box. 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 discovered close to a squirrels mouth or eye.
However, Eastern Gray Squirrels have had a positive impact on human life. For example, they helped Native Americans access food. In some states like Mississippi, they have helped harvest 2.5 million dollars in crops annually, which helped Mississippi gain 12.5 million dollars.
Habitat
Eastern gray squirrel are always on the go. As they prepare for the coming days, the squirrels gather their food and hide it in various places. Through the morning and afternoon, squirrels search for food. During their breeding season, a male and female squirrel may occasionally share a nest. A pregnant female squirrel stays by herself in her nest and when it is time to breastfeed, the male squirrels don't bother them. In the wild, eastern gray squirrels can be found inhabiting large areas of mature, dense woodland
A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...
ecosystems, generally covering 100 acres (40 hectares) of land. These forests usually contain large mast
Mast, MAST or MASt may refer to:
Engineering
* Mast (sailing), a vertical spar on a sailing ship
* Flagmast, a pole for flying a flag
* Guyed mast, a structure supported by guy-wires
* Mooring mast, a structure for docking an airship
* Radio mast ...
-producing trees such as oaks and hickories, providing ample food sources. Oak-hickory hardwood forests are generally preferred over coniferous forests due to the greater abundance of mast forage. This is why they are found only in parts of eastern Canada which do not contain boreal forest (i.e. they are found in some parts of New Brunswick, in southwestern Quebec, throughout southern Ontario and in southern Manitoba).
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.
Eastern gray Squirrels also use dens for protection from prey and helps 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. Covers like Canopy and Midstory Trees are used by Squirrels to hide from prey such as Hawks and Owls. These squirrels homes range from 1.5 to 8 acres and tend to be smaller where more of them are found.
Close to human settlements, eastern gray squirrels are found in parks and back yards of houses within urban environments and in the farmlands of rural environments.
Introductions
The eastern gray squirrel is an introduced species
An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived the ...
in a variety of locations in western North America: in western Canada
Western Canada, also referred to as the Western provinces, Canadian West or the Western provinces of Canada, and commonly known within Canada as the West, is a Canadian region that includes the four western provinces just north of the 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 () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...
and, in California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...
, to the city of San Francisco
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
and the San Francisco Peninsula
The San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is Mountain View, south of Palo Alt ...
area in San Mateo and Santa Clara 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.
By the turn of the 20th century, breeding populations of the eastern gray squirrel had been introduced into South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...
, Ireland
Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
, Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
, Australia (extirpated by 1973), and the United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
.
In South Africa, though exotic, it is not usually considered an invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
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
Franschhoek (; Afrikaans for "French Corner", Dutch spelling before 1947 ''Fransche Hoek'') is a small town in the Western Cape Province and one of the oldest towns in South Africa. Formerly known as Oliphants hoek (as there were vast groups of ...
), 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
Smith's bush squirrel (''Paraxerus cepapi''), also known as the yellow-footed squirrel or tree squirrel, is an African bush squirrel which is native to woodlands of the southern Afrotropics.
Range
It is found in Angola, Botswana, the DRCongo, ...
'', 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
''The Times'' is a British daily national newspaper based in London. It began in 1785 under the title ''The Daily Universal Register'', adopting its current name on 1 January 1788. ''The Times'' and its sister paper '' The Sunday Times'' ...
that the Zoological Society of London
The Zoological Society of London (ZSL) is a charity devoted to the worldwide conservation of animals and their habitats. It was founded in 1826. Since 1828, it has maintained the London Zoo, and since 1931 Whipsnade Park.
History
On 29 ...
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.[
In Ireland, the displacement of red squirrels has not been as rapid because only a single introduction occurred, in ]County Longford
County Longford ( gle, Contae an Longfoirt) is a county in Ireland. It is in the province of Leinster. It is named after the town of Longford. Longford County Council is the local authority for the county. The population of the county was ...
. Schemes have been introduced to control the population of gray squirrels in Ireland to encourage the native red squirrels. Eastern gray squirrels have also been introduced to Italy, and the European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...
has expressed concern that they will similarly displace the red squirrel from parts of the European continent.
Displacement of red squirrels
In Britain and Ireland, the eastern gray squirrel is not regulated by natural predators, other than the European pine marten
The European pine marten (''Martes martes''), also known as the pine marten, is a mustelid native to and widespread in most of Europe, Asia Minor, the Caucasus and parts of Iran, Iraq and Syria. It is listed as Least Concern on the IUCN R ...
, 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
Pest or The Pest may refer to:
Science and medicine
* Pest (organism), an animal or plant deemed to be detrimental to humans or human concerns
** Weed, a plant considered undesirable
* Infectious disease, an illness resulting from an infection
** ...
. 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
The Forestry Commission is a non-ministerial government department responsible for the management of publicly owned forests and the regulation of both public and private forestry in England.
The Forestry Commission was previously also respo ...
providing a regular supply of squirrel meat to British restaurants, factories and butchers. In areas where relict populations of red squirrel
The red squirrel (''Sciurus vulgaris'') is a species of tree squirrel in the genus '' Sciurus'' common throughout Europe and Asia. The red squirrel is an arboreal, primarily herbivorous rodent.
In Great Britain, Ireland, and in Italy numbers ...
s survive, such as the islands of Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a Local government in Wales, principal area known as the Isle of Anglesey, that includes Holy Island, Anglesey, Holy Island across the narrow Cymyran Strai ...
, Brownsea
Brownsea Island is the largest of the islands in Poole Harbour in the county of Dorset, England. The island is owned by the National Trust with the northern half managed by the Dorset Wildlife Trust. Much of the island is open to the public and ...
and the Isle of Wight
The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...
, programs exist to eradicate gray squirrels and prevent them from reaching these areas in order to allow red squirrel populations to recover and grow.
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, hence a competitive advantage over the red squirrel on all measures. Within 15 years of the grey squirrel's introduction to a red squirrel habitat, 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 lack 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. 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 may also be a strongly contributing factor; red squirrels have long been fatally affected by the disease, while the eastern gray squirrels are unaffected, but thought to be carriers – although how the virus is transmitted has yet to be determined. Red squirrel extinction rates can be 20–25 times greater in areas with confirmed cases of squirrel pox than they are in areas without the disease. his competitive action done between these two squirrels is reasoned to qualify the eastern gray squirrel as a keystone species because since the eastern gray squirrel is coming and wiping out the red squirrels, there would be a reduced chance of competition hence more eastern gray squirrels will come in to Ireland. However, several cases of red squirrels surviving have been reported, as they have developed an immunity – although their population is still being massively affected. The red squirrel is also less tolerant of habitat destruction
Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
and fragmentation, which has led to its population decline, while the more adaptable eastern gray squirrel has taken advantage and expanded. Methods done to control this competition between these squirrels are that red squirrels should remain in their original habitats, such as Ireland, while the grey squirrels should be kept out of these places entirely as a means of controlling this squirrel competition.
Similar factors appear to have been at play in the Pacific region of North America, where the native American red squirrel
The American red squirrel (''Tamiasciurus hudsonicus'') is one of three species of tree squirrels currently classified in the genus ''Tamiasciurus'', known as the pine squirrels (the others are the Douglas squirrel, ''T. douglasii'', and the sou ...
has been largely displaced by the eastern gray squirrel in parks and forests throughout much of the region.
Ironically, "fears" for the future of the eastern gray squirrel arose in 2008, 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
The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom implemented to comply with European Council Directive 79/409/EEC on the conservation of wild birds. In short, the act gives protection to native species (especia ...
, it is illegal to release it or to allow it to escape into the wild; instead, it is legally required be "humanely dispatched".
In the late 1990s, Italy's National Wildlife Institute and University of Turin launched an eradication attempt to halt the spread of gray squirrels in northwest Italy, but court action by animal rights groups blocked this. Hence gray squirrels are expected to cross the Alps into France and Switzerland in the next few decades.
Ecosystem
Eastern Grey Squirrels are important to the ecosystem by eating a lot of seeds. By caching seeds, they help in the spread of tree seeds. Also, by eating truffles, they contribute to the spread of fungal spores. In addition, they are essential to the environment because they transport parasites. The ecology is influenced by the contribution of squirrels to nature. They support the environment by gathering seeds. While being gathered, the seeds are scattered in certain places. Even though the seeds are not helpful to the squirrels because they can't remember where they were hidden, they are still growing in nature. These seeds increase the diversity of trees by bringing additional trees into the environment. They are an important key to the forest ecosystem that they belong to.
Fossil record of the eastern gray squirrel
Twenty different Pleistocene fauna specimens contain ''S. carolinensis'', found in Florida and dated to be 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.
]
As food
Gray squirrels were eaten in earlier times by Native Americans and their meat is still popular with hunters across most of their range in North America. Today, it is still available for human consumption and is occasionally sold in the United Kingdom. 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
Creutzfeldt–Jakob disease (CJD), also known as subacute spongiform encephalopathy or neurocognitive disorder due to prion disease, is an invariably fatal degenerative brain disorder. Early symptoms include memory problems, behavioral changes ...
.
See also
* Black squirrel
Black squirrels are a melanistic subgroup of squirrels with black coloration on their fur. The phenomenon occurs with several species of squirrels, although it is most frequent with the eastern gray squirrel (''Sciurus carolinensis'') and the ...
, a melanistic subgroup
* Western gray squirrel (''Sciurus griseus'')
* Arizona gray squirrel (''Sciurus arizonensis'')
* Mexican gray squirrel (''Sciurus aureogaster'')
* Tommy Tucker (squirrel)
Tommy Tucker (before/in 1942 – June 25, 1949) was a male Eastern gray squirrel who became a celebrity in the United States, touring the country wearing women's fashions while performing tricks, entertaining children, and selling war bonds. A ...
, a celebrity eastern gray squirrel in the 1940s
References
External links
ARKive
– Still photos and videos
– an article from The Washington Post
''The Washington Post'' (also known as the ''Post'' and, informally, ''WaPo'') is an American daily newspaper published in Washington, D.C. It is the most widely circulated newspaper within the Washington metropolitan area and has a large n ...
WildlifeOnline – Natural History of Tree Squirrels
Smithsonian Eastern Gray Squirrel article
Grey Squirrel feeding on peanuts in a British park
Grey Squirrels
Fletcher Wildlife Garden
{{Taxonbar, from=Q468500
Eastern gray squirrel
The eastern gray squirrel (''Sciurus carolinensis''), also known, particularly outside of North America, as simply the grey squirrel, is a tree squirrel in the genus '' Sciurus''. It is native to eastern North America, where it is the most pro ...
Mammals of Canada
Mammals of the United States
Rodents of North America
Eastern gray squirrel
The eastern gray squirrel (''Sciurus carolinensis''), also known, particularly outside of North America, as simply the grey squirrel, is a tree squirrel in the genus '' Sciurus''. It is native to eastern North America, where it is the most pro ...
Eastern gray squirrel
The eastern gray squirrel (''Sciurus carolinensis''), also known, particularly outside of North America, as simply the grey squirrel, is a tree squirrel in the genus '' Sciurus''. It is native to eastern North America, where it is the most pro ...
Symbols of North Carolina