The fox squirrel (''Sciurus niger''), also known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. Despite the differences in size and coloration, it is sometimes mistaken for

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 ...

s or eastern gray squirrels in areas where the species co-exist. There is no sexual dimorphism in size or appearance. Individuals tend to be smaller in the west. There are three distinct geographical phases in coloration: In most areas the animal's upper body is brown-grey to brown-yellow with a typically brownish-orange underside, while in eastern regions such as the Appalachians there are more strikingly-patterned dark brown and black squirrels with white bands on the face and tail. In the south are isolated communities with uniform black coats. To help with climbing, the squirrels have sharp claws, developed

extensors In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendin ...

of digits and flexors of forearms, and abdominal musculature. Fox squirrels have excellent vision and well-developed senses of hearing and smell. They use scent marking to communicate with other fox squirrels. "Fox squirrels also have several sets of vibrissae, hairs or whiskers that are used as touch receptors to sense the environment. These are found above and below their eyes, on their chin and nose, and on each forearm." The dental formula of ''S. niger'' is . Fox squirrel Indy

Distribution

The fox squirrel's natural range extends through most of the eastern United States, north into the southern prairie provinces of Canada, and west to the

Dakotas The Dakotas is a collective term for the U.S. states of North Dakota and South Dakota. It has been used historically to describe the Dakota Territory, and is still used for the collective heritage, culture, geography, fauna, sociology, econom ...

, Colorado, and Texas. They are absent (except for vagrants) in New England, New Jersey, most of

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

, northern and eastern Pennsylvania, Ontario, Quebec, and the Atlantic provinces of Canada. They have been introduced to both northern and southern California, Oregon, Idaho, Montana, Washington, and New Mexico, as well as Ontario and British Columbia in Canada. While very versatile in their habitat choices, fox squirrels are most often found in forest patches of 40 hectares or less with an open understory, or in urban neighborhoods with trees. They thrive best among oak,

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 ...

, walnut, pecan and pine trees, storing their nuts for winter. Western range extensions in

Great Plains The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...

regions such as Kansas are associated with riverine corridors of cottonwood. A

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

native to several eastern US states is the

Delmarva fox squirrel The Delmarva fox squirrel (''Sciurus niger cinereus'') is a formerly endangered subspecies of the fox squirrel. It is native to the eastern United States. The Delmarva fox squirrel was removed from the endangered species list in November 2015. B ...

(''S. n. cinereus'').Van Gelden, Richard George. (1982). Mammals of the National Parks. Baltimore, MD: Johns Hopkins University Press

Invasiveness

In Europe, ''Sciurus niger'' 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.

Habitat

Fox squirrels are most abundant in open forest stands with little understory vegetation; they are not found in stands with dense undergrowth. Ideal habitat is small stands of large trees interspersed with agricultural land. The size and spacing of

pines A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accep ...

and oaks are among the important features of fox squirrel habitat. The actual species of pines and oaks themselves may not always be a major consideration in defining fox squirrel habitat. Fox squirrels are often observed foraging on the ground several hundred meters from the nearest woodlot. Fox squirrels also commonly occupy forest edge habitat. Fox squirrels have two types of shelters: leaf nests (

drey A drey is the nest of a tree squirrel, flying squirrel or ringtail possum. Dreys are usually built of twigs, dry leaves, and grass, and typically assembled in the forks of a tall tree. They are sometimes referred to as "drey nests" to disting ...

s) and tree dens. They may have two tree cavity homes or a tree cavity and a leaf nest. Tree dens are preferred over leaf nests during the winter and for raising young. When den trees are scarce, leaf nests are used year-round.Banfield, A. W. F. (1974). The mammals of Canada. Toronto, ON: University of Toronto Press.MacClintock, Dorcas. (1970). Squirrels of North America. New York: Litton Educational Publishing, Inc. Leaf nests are built during the summer months in forks of deciduous trees about 30 feet (9 m) above the ground. Fox squirrels use natural cavities and crotches (forked branches of a tree) as tree dens. Den trees in Ohio had an average diameter at breast height (d.b.h.) of and were an average of from the nearest woodland border. About 88% of den trees in eastern Texas had an average d.b.h. ( diameter at breast height) of or more. Dens are usually wide and inches deep. Den openings are generally circular and about . Fox squirrels may make their own den in a hollow tree by cutting through the interior; however, they generally use natural cavities or cavities created by

northern flicker The northern flicker or common flicker (''Colaptes auratus'') is a medium-sized bird of the woodpecker family. It is native to most of North America, parts of Central America, Cuba, and the Cayman Islands, and is one of the few woodpecker spec ...

s (''Colaptes auratus'') or red-headed woodpeckers (''Melanerpes erythrocephalus''). Crow nests have also been used by fox squirrels. Fox squirrels use leaf nests or tree cavities for shelter and litter rearing. Forest stands dominated by mature to over mature trees provide cavities and a sufficient number of sites for leaf nests to meet the cover requirements. Overstory trees with an average d.b.h. of or more generally provide adequate cover and reproductive habitat. Optimum tree canopy closure for fox squirrels is from 20% to 60%. Optimum conditions of understory closure occur when the shrub-crown closure is 30% or less.Allen, A. W. 1982. Habitat suitability index models: fox squirrel. FWS/OBS-82/10.18. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service Fox squirrels are tolerant of human proximity, and even thrive in crowded urban and suburban environments. They exploit human habitations for sources of food and nesting sites, being as happy nesting in an attic as they are in a hollow tree.

Diet

Eastern Fox Squirrel in Berkeley California garden-Oct 2014

Food habits of fox squirrels depend largely on geographic location.Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press In general, fox squirrel foods include

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 ...

, tree

buds In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specia ...

, insects, tubers,

bulbs In botany, a bulb is structurally a short stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs durin ...

roots A root is the part of a plant, generally underground, that anchors the plant body, and absorbs and stores water and nutrients. Root or roots may also refer to: Art, entertainment, and media * ''The Root'' (magazine), an online magazine focusing ...

, bird eggs, pine seeds and spring-fruiting trees, and fungi. Agricultural crops such as

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 ...

soybeans The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu and ...

, oats, wheat, and fruit are also eaten. Mast eaten by fox squirrels commonly includes turkey oak ('' Quercus laevis''), southern red oak (''

Quercus falcata ''Quercus falcata'', also called southern red oak, spanish oak, bottomland red oak or three-lobed red oak is an oak (part of the genus ''Quercus''). Native to the southeastern United States, it gets its name the "Spanish Oak" as these are the ar ...

''), blackjack oak ('' Quercus marilandica''), bluejack oak ('' Quercus incana''), post oak ('' Quercus stellata''), and live oak ('' Quercus virginiana''). In Illinois, fox squirrels rely heavily on hickories from late August through September. Pecans, black walnuts ('' Juglans nigra''), osage orange ('' Maclura pomifera'') fruits, and corn are also important fall foods. In early spring, elm buds and seeds are the most important food. In May and June, mulberries ('' Morus'' spp.) are heavily used. By early summer, corn in the milk stage becomes a primary food. During the winter in Kansas, osage orange is a staple item supplemented with seeds of the Kentucky coffee tree ('' Gymnocladus dioicus'') and honey locust (''

Gleditsia triacanthos The honey locust (''Gleditsia triacanthos''), also known as the thorny locust or thorny honeylocust, is a deciduous tree in the family Fabaceae, native to central North America where it is mostly found in the moist soil of river valleys. Honey ...

''), corn, wheat,

eastern cottonwood ''Populus deltoides'', the eastern cottonwood or necklace poplar, is a cottonwood poplar native to North America, growing throughout the eastern, central, and southwestern United States as well as the southern Canadian prairies, the southernm ...

(''Populus deltoides'' var. ''deltoides'') bark, ash seeds, and eastern red cedar ('' Juniperus virginiana'') berries. In the spring, fox squirrels feed primarily on buds of elm, maple, and oaks but also on newly sprouting leaves and insect larvae. Fox squirrels in Ohio prefer hickory nuts, acorns, corn, and black walnuts. The squirrels are absent where two or more of these mast trees are missing. Fox squirrels also eat buckeyes, seeds and buds of maple and elm, hazelnuts ('' Corylus'' spp.), blackberries ('' Rubus'' spp.), and tree bark. In March, they feed mainly on buds and seeds of elm, maple, and willow. In Ohio, eastern fox squirrels have the following order of food preference: white oak ('' Quercus alba'') acorns, black oak ('' Quercus velutina'') acorns, red oak (''

Quercus rubra ''Quercus rubra'', the northern red oak, is an oak tree in the red oak group (''Quercus'' section ''Lobatae''). It is a native of North America, in the eastern and central United States and southeast and south-central Canada. It has been introdu ...

'') acorns, walnuts, and corn. In eastern Texas, fox squirrels prefer the acorns of bluejack oak, pecans, southern red oak (''Q. falcata''), and overcup oak (''Q. lyrata''). The least preferred foods are acorns of swamp chestnut oak (''Q. michauxii'') and overcup oak. In California, fox squirrels feed on English walnuts (''J. regia''), oranges, avocados, strawberries, and tomatoes. In midwinter, they feed on eucalyptus seeds. In Michigan, fox squirrels feed on a variety of foods throughout the year. Spring foods are mainly tree buds and flowers, insects, bird eggs, and seeds of red maple ('' Acer rubrum''), silver maple ('' Acer saccharinum''), and elms. Summer foods include a variety of berries, plum and cherry pits, fruits of basswood (''

Tilia americana ''Tilia americana'' is a species of tree in the family Malvaceae, native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Oklahoma, southeast to South Carolina, and west along the Niobrara River to ...

''), fruits of box elder (''

Acer negundo ''Acer negundo'', the box elder, boxelder maple, Manitoba maple or ash-leaved maple, is a species of maple native to North America. It is a fast-growing, short-lived tree with opposite, compound leaves. It is sometimes considered a weedy or inv ...

''), black oak acorns, hickory nuts, seeds of sugar (''

Acer saccharum ''Acer saccharum'', the sugar maple, is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is native to the hardwood forests of eastern Canada and eastern United States. Sugar maple is best known for being the prima ...

'') and black maple ('' Acer nigrum''), grains, insects, and unripe corn. Fall foods consist mainly of acorns, hickory nuts, beechnuts, walnuts, butternuts ('' Juglans cinerea''), and hazelnuts. Caches of acorns and hickory nuts are heavily used in winter.

Behavior

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 "

s", 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 will form caches by burying food items for later consumption. They like to store foods that are shelled and high in fat, such as acorns and nuts. Shelled foods are favored because they are less likely to spoil than non-shelled foods, and fatty foods are valued for their high energy density. They are not particularly gregarious or playful, in fact they have been described as solitary and asocial creatures, coming together only in breeding season. Relatively few natural predators can regularly capture adult fox squirrels. Of these predators, most only take fox squirrels opportunistically. Predators include:

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 IUC ...

s (''Lynx rufus''), Canada lynx (''Lynx canadensis''),

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''). Twelve sp ...

es (''Vulpes vulpes'' and ''Urocyon cinereoargenteus''), red-tailed hawks (''Buteo jamaicensis''), red-shouldered hawks (''Buteo lineatus''), great horned owls (''Bubo virginianus''), barred owls (''Strix varia''), and

coyote The coyote (''Canis latrans'') is a species of canis, canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecologica ...

s (''Canis latrans''). Former predators extirpated from most of the fox squirrel's range included

cougar The cougar (''Puma concolor'') is a large Felidae, cat native to the Americas. Its Species distribution, range spans from the Canadian Yukon to the southern Andes in South America and is the most widespread of any large wild terrestrial mamm ...

s (''Puma concolor'') and gray wolves (''Canis lupus''). Nestlings and young fox squirrels are particularly vulnerable to climbing predators such as raccoons (''Procyon lotor''),

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...

s (''Didelphis virginiana''), rat snakes (''Pantherophis spp.''), and

pine snake Pine snake may refer to: * '' Pituophis melanoleucus'', a nonvenomous colubrid found in North America * '' Lampropeltis g. getula'', a.k.a. the eastern kingsnake, a nonvenomous colubrid found in the eastern United States * '' Pantherophis vulpinus' ...

s (''Pituophis melanoleucus''). In those states where fox squirrels are not protected, they are considered a game animal. Fox squirrels were an important source of meat for European settlers in the 17th and 18th centuries. They are still hunted over most of their range. Overhunting has been reported from small woodlots and public shooting areas in Ohio, Michigan, and Indiana.

References

External links

*
Enature treatment: Eastern Fox Squirrel (''Sciurus niger'')

American Society of Mammalogists: Mammalian species account of ''Sciurus niger''

Smithsonian: Eastern Fox Squirrel article

Digimorph: 3D visualization of a Fox Squirrel skull

The Squirrel Project
��UIC study of territorial interleavings of Grey and Fox Squirrels, in urban Chicago {{Taxonbar, from=Q694296 Fox squirrel Mammals of Canada Mammals of the United States Rodents of North America Fauna of the Eastern United States Fauna of the Plains-Midwest (United States) Mammals described in 1758 Taxa named by Carl Linnaeus Articles containing video clips Least concern biota of North America Least concern biota of the United States