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

tree squirrel Tree squirrels are the members of the squirrel Family (biology), family (Sciuridae) commonly just referred to as "squirrels". They include more than 100 arboreal species native to all continents except Antarctica and Oceania. They do not form a ...

native to

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. It is sometimes mistaken for 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 ...

or eastern gray squirrel in areas where the species co-exist, though they differ in size and coloration.

Description

The fox squirrel's total length measures , with a body length of and a similar tail length. They range in weight from . There is no

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

in size or appearance. Individuals tend to be smaller in the West. There are three distinct geographical morphs 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 The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

, there are more strikingly-patterned dark brown and black squirrels with white bands on the face and tail. In the South and parts of

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

and

Iowa Iowa ( ) is a U.S. state, state in the upper Midwestern United States, Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Ill ...

along the Missouri River, there are populations with uniform black coats. Fox Squirrel in Central Florida

To help with climbing, the squirrels have sharp claws, developed

extensor 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 extend ...

s of digits and

flexor In anatomy, flexor is a muscle that contracts to perform flexion (from the Latin verb ''flectere'', to bend), a movement that decreases the angle between the bones converging at a joint. For example, one's elbow joint flexes when one brin ...

s of forearms, and abdominal

musculature Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

. 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 .

Distribution and habitat

The fox squirrel's natural range extends through most of the eastern

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, north into the southern prairie provinces of

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, west to the

Dakotas The Dakotas, also known as simply Dakota, 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, geo ...

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

, and

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, and south to the northern parts of

Coahuila Coahuila, formally Coahuila de Zaragoza, officially the Free and Sovereign State of Coahuila de Zaragoza, is one of the 31 states of Mexico. The largest city and State Capital is the city of Saltillo; the second largest is Torreón and the thi ...

Nuevo León Nuevo León, officially the Free and Sovereign State of Nuevo León, is a Administrative divisions of Mexico, state in northeastern Mexico. The state borders the Mexican states of Tamaulipas, Coahuila, Zacatecas, and San Luis Potosí, San Luis ...

(as far south as the Valle de las Salinas) and

Tamaulipas Tamaulipas, officially the Free and Sovereign State of Tamaulipas, is a state in Mexico; one of the 31 states which, along with Mexico City, comprise the 32 federal entities of Mexico. It is divided into 43 municipalities. It is located in nor ...

. It is absent (except for vagrants) in

New England New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

, most of

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

, northern and eastern

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...

, and the

Atlantic provinces Atlantic Canada, also called the Atlantic provinces (), is the region of Eastern Canada comprising four provinces: New Brunswick, Newfoundland and Labrador, Nova Scotia, and Prince Edward Island. As of 2021, the landmass of the four Atlantic pr ...

of Canada. It has been introduced to both northern and southern

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

Idaho Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

, and

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

, as well as Ontario and

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

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 among

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

hickory Hickory is a common name for trees composing the genus ''Carya'', which includes 19 species accepted by ''Plants of the World Online''. Seven species are native to southeast Asia in China, Indochina, and northeastern India (Assam), and twelve ...

walnut A walnut is the edible seed of any tree of the genus '' Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. They are accessory fruit because the outer covering of the fruit is technically an i ...

pecan The pecan ( , , ; ''Carya illinoinensis'') is a species of hickory native to the Southern United States and northern Mexico in the region of the Mississippi River. The tree is cultivated for its seed primarily in the U.S. states of Georgia ( ...

and

pine 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. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

trees, storing their nuts for winter. Western range extensions in

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

regions such as

Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...

are associated with riverine corridors of cottonwood. Some

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

native to several eastern U.S. states are the Delmarva Peninsula fox squirrel (''S. n. cinereus''),Van Gelden, Richard George. (1982). Mammals of the National Parks. Baltimore, MD: Johns Hopkins University Press and the

southern fox squirrel The Southern fox squirrel (''Sciurus niger niger)'' is a subspecies of the fox squirrel. They are native to the eastern United States and currently reside in North Carolina, South Carolina, and Georgia (U.S. state), Georgia. They can also be found ...

(S. n. niger). 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 Agricultural land is typically land ''devoted to'' agriculture, the systematic and controlled use of other organism, forms of lifeparticularly the rearing of livestock and production of cropsto produce food for humans. It is generally synonymous ...

. The size and spacing of

s and

s 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 A woodlot is a parcel of a woodland or forest capable of small-scale production of forest products (such as wood fuel, sap for maple syrup, sawlogs, and pulpwood) as well as recreational uses like bird watching, bushwalking, and wildflower appre ...

. 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 western ringtail possum, 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 a ...

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 Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements. Tree trunks are measured at the height of an adult's breast, ...

(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. (

) 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 specie ...

s (''Colaptes auratus'') or

red-headed woodpecker The red-headed woodpecker (''Melanerpes erythrocephalus'') is a mid-sized woodpecker found in temperate North America. Its breeding habitat is open country across southern Canada and the east-central United States. It is rated as least concern ...

s (''Melanerpes erythrocephalus'').

Crow A crow is a bird of the genus ''Corvus'', or more broadly, a synonym for all of ''Corvus''. The word "crow" is used as part of the common name of many species. The related term "raven" is not linked scientifically to any certain trait but is rathe ...

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.

As an invasive species

In Europe, ''Sciurus niger'' has been included since 2016 in the

list of Invasive Alien Species of Union concern In 2016, following the EU Regulation 1143/2014 on Invasive species, Invasive Alien Species (IAS), the European Commission published a first list of 37 IAS of Union concern. The list was first updated in 2017 and comprised 49 species. Since the sec ...

(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.

Behavior and ecology

Eastern Fox Squirrel in Berkeley California garden-Oct 2014

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. Fox squirrels are not particularly gregarious or playful; in fact, they have been described as solitary and asocial creatures, coming together only in breeding season. They have a large vocabulary, consisting most notably of an assortment of clucking and chucking sounds, not unlike some "game" birds, and they warn of approaching threats with distress screams. In the spring and autumn, groups of fox squirrels clucking and chucking together can make a small ruckus. They also make high-pitched whines during mating. When threatening another fox squirrel, they will stand upright with their tail over their back and flick it. Fox squirrels are impressive jumpers, easily spanning 15 feet in horizontal leaps and free-falling 20 feet or more to a soft landing on a tree limb or tree trunk.

Diet

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 mas ...

, tree

bud In botany, a bud is an undeveloped or Plant embryogenesis, embryonic Shoot (botany), shoot and normally occurs in the axil of a leaf or at the tip of a Plant stem, stem. Once formed, a bud may remain for some time in a dormancy, dormant conditi ...

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

tuber Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduc ...

bulb In botany, a bulb is a short underground 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 duri ...

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

bird egg Bird eggs are laid by the females and range in quantity from one (as in condors) to up to seventeen (the grey partridge). Avian clutch size, Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been ...

pine nut Pine nuts, also called piñón (), pinoli (), or pignoli, are the edible seeds of pines (family Pinaceae, genus ''Pinus''). According to the Food and Agriculture Organization, only 29 species provide edible nuts, while 20 are traded locall ...

s and spring-fruiting trees, and

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

. Agricultural crops such as

corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

oat The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have been domesticated as a secondary crop, as their seeds ...

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

, and fruit are also eaten. Mast eaten by fox squirrels commonly includes turkey oak (''

Quercus laevis ''Quercus laevis'', the turkey oak, is a member of the red oak group of oaks. It is native to the southeastern United States. The name turkey oak derives from the resemblance of the leaves to a turkey's foot. A Turkish and southern European spe ...

''), southern red oak ('' Quercus falcata''), blackjack oak (''

Quercus marilandica ''Quercus marilandica'', the blackjack oak, is a small oak, one of the red oak group ''Quercus'' sect. ''Lobatae''. It is native to the eastern and central United States. Description ''Quercus marilandica'' is a small deciduous tree growing to ...

''), bluejack oak (''

Quercus incana ''Quercus incana'' is a species of oak known by the common names bluejack oak, upland willow oak, sandjack oak, and cinnamon oak. It is native to the Atlantic and Gulf coastal plains of the United States, from Virginia around Florida to Texas and ...

''), post oak (''

Quercus stellata ''Quercus stellata'', the post oak or iron oak, is a North American species of oak in the white oak section. It is a slow-growing oak that lives in dry areas on the edges of fields, tops of ridges, and also grows in poor soils, and is resistan ...

''), and live oak (''

Quercus virginiana ''Quercus virginiana'', also known as the southern live oak, is an evergreen oak tree endemic to the Southeastern United States. Though many other species are loosely called live oak, the southern live oak is particularly iconic of the Old South. ...

'').

In Illinois, fox squirrels rely heavily on hickories from late August through September. Pecans, black walnuts (''

Juglans nigra ''Juglans nigra'', the eastern American black walnut, is a species of deciduous tree in the walnut family, Juglandaceae, native to central and eastern North America, growing mostly in riparian zones. Black walnut is susceptible to thousand can ...

''), osage orange (''

Maclura pomifera ''Maclura pomifera'', commonly known as the Osage orange ( ), is a small deciduous tree or large shrub, native to the south-central United States. It typically grows about tall. The distinctive fruit, a multiple fruit that resembles an immatur ...

'') 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. Fox Squirrel Storing Food

During the winter in Kansas, osage orange is a staple item supplemented with seeds of the Kentucky coffee tree (''

Gymnocladus dioicus The Kentucky coffeetree (''Gymnocladus dioicus''), also known as American coffee berry, Kentucky mahogany, nicker tree, and stump tree, is a tree in the subfamily Caesalpinioideae of the legume family Fabaceae, native to the Midwestern United Sta ...

'') 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'' var. ''deltoides'') bark, ash seeds, and eastern red cedar (''

Juniperus virginiana ''Juniperus virginiana'', also known as eastern redcedar, red cedar, Virginian juniper, eastern juniper, red juniper, and other local names, is a species of juniper native to eastern North America from southeastern Canada to the Gulf of Mexico an ...

'') 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 Hazels are plants of the genus ''Corylus'' of deciduous trees and large shrubs native to the temperate Northern Hemisphere. The genus is usually placed in the birch family, Betulaceae,Germplasmgobills Information Network''Corylus''Rushforth, ...

'' spp.),

blackberries BlackBerry is a discontinued brand of handheld devices and related mobile services, originally developed and maintained by the Canadian company Research In Motion (RIM, later known as BlackBerry Limited) until 2016. The first BlackBerry device ...

(''

Rubus ''Rubus'' is a large and diverse genus of flowering plants in the rose family, Rosaceae, subfamily Rosoideae, most commonly known as brambles. Fruits of various species are known as raspberries, blackberries, dewberries, and bristleberries. ...

'' 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 ''Quercus alba'', the white oak, is one of the preeminent hardwoods of eastern and central North America. It is a long-lived oak, native to eastern and central North America and found from Minnesota, Ontario, Quebec, and southern Maine south as ...

'') acorns, black oak (''

Quercus velutina ''Quercus velutina'' (Latin 'velutina', "velvety") , the black oak, is a species of oak in the red oak group (''Quercus'' sect. ''Lobatae''), native and widespread in eastern and central North America. It is sometimes called the eastern black oak ...

'') 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 intro ...

'') 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 ''Acer rubrum'', the red maple, also known as swamp maple, water maple, or soft maple, is one of the most common and widespread deciduous trees of eastern and central North America. The U.S. Forest Service recognizes it as the most abundant nati ...

''), silver maple (''

Acer saccharinum ''Acer saccharinum'', commonly known as silver maple, creek maple, silverleaf maple, soft maple, large maple, water maple, swamp maple, or white maple, is a species of maple native to the eastern and central United States and southeastern Canad ...

''), 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'', also known as the box elder, boxelder maple, Manitoba maple or ash-leaved maple, is a species of maple native to North America from Canada to Honduras. It is a fast-growing, short-lived tree with opposite, ash-like compound l ...

''), 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 the eastern United States. Sugar maple is best known for being the p ...

'') and black maple (''

Acer nigrum ''Acer nigrum'', the black maple, is a species of maple closely related to '' A. saccharum'' (sugar maple), and treated by some authors as a subspecies of it, as ''Acer saccharum'' subsp. ''nigrum''. Identification can be confusing due to the t ...

''), grains, insects, and unripe corn. Autumn foods consist mainly of acorns, hickory nuts, beechnuts, walnuts, butternuts (''

Juglans cinerea ''Juglans cinerea'', commonly known as butternut or white walnut,Snow, Charles Henry ''The Principal Species of Wood: Their Characteristic Properties'' 2nd ed. New York: John Wiley & Sons, 1908. p. 56. is a species of walnut native to the e ...

''), and hazelnuts. Caches of acorns and hickory nuts are heavily used in winter.

Reproduction

Female fox squirrels come into estrus in mid-December or early January, then again in June. They normally produce two litters a year; however, yearling females may only produce one. Females become sexually mature at 10 to 11 months of age and usually produce their first litter when they are 1 year old.

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 pregn ...

occurs over a period of 44 to 45 days. The earliest litters appear in late January; most births occur in mid-March and July. The average litter size is three, but can vary according to season and food conditions. Tree cavities, usually those formed by

woodpecker Woodpeckers are part of the bird family (biology), family Picidae, which also includes the piculets, wrynecks and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar and the extreme ...

s, are remodeled into winter dens and often serve as nurseries for late winter litters. If existing trees lack cavities, leaf nests known as

s are built by cutting twigs with leaves and weaving them into warm, waterproof shelters. Similar leafy platforms are built for summer litters and are often called "cooling beds." Fox squirrels, like other tree squirrels, develop slowly compared to others. At birth, the young are blind, without fur, and helpless. Their eyes open at 4 to 5 weeks and their ears open at 6 weeks. Fox squirrels are weaned between 12 and 14 weeks, but may not be self-supporting until 16 weeks. Juveniles usually disperse in September or October, but may den either together or with their mother during their first winter.

Mortality

In captivity, fox squirrels have been known to live about 18 years, but in the wild, most fox squirrels die before they become adults. Their maximum life expectancy is typically 12.6 years for females and 8.6 years for males. Because of overhunting and the destruction of mature forests, many subspecies of fox squirrel are

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

. Another major cause of fox squirrel population decline is mange mites (''Cnemidoptes'' spp.) along with severe winter weather. 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 wildcat, bay lynx, or red lynx, is one of the four extant species within the medium-sized wild cat genus '' Lynx''. Native to North America, it ranges from southern Canada through most of the c ...

s (''Lynx rufus''),

Canada lynx The Canada lynx (''Lynx canadensis'') or Canadian lynx is one of the four living species in the genus ''Lynx''. It is a medium-sized wild cat characterized by long, dense fur, triangular ears with black tufts at the tips, and broad, snowshoe- ...

(''Lynx canadensis''),

red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia, plus ...

es (''Vulpes vulpes''),

gray fox The gray fox (''Urocyon cinereoargenteus''), or grey fox, is an omnivorous mammal of the family Canidae, widespread throughout North America and Central America. This species and its only congener (biology), congener, the diminutive island fox ...

es (''Urocyon cinereoargenteus''),

red-tailed hawk The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members of ...

s (''Buteo jamaicensis''),

red-shouldered hawk The red-shouldered hawk (''Buteo lineatus'') is a medium-sized buteo. Its breeding range spans eastern North America and along the coast of California and northern to northeastern-central Mexico. It is a permanent resident throughout most of its ...

s (''Buteo lineatus''),

great horned owl The great horned owl (''Bubo virginianus''), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air") or the hoot owl, is a large owl native to the Americas. It is an extreme ...

s (''Bubo virginianus''),

barred owl The barred owl (''Strix varia''), also known as the northern barred owl, striped owl or, more informally, hoot owl or eight-hooter owl, is a North American large species of owl. A member of the true owl family, Strigidae, they belong to the genus ...

s (''Strix varia''), and

coyote The coyote (''Canis latrans''), also known as the American jackal, prairie wolf, or brush wolf, is a species of canis, canine native to North America. It is smaller than its close relative, the Wolf, gray wolf, and slightly smaller than the c ...

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

cougar The cougar (''Puma concolor'') (, ''Help:Pronunciation respelling key, KOO-gər''), also called puma, mountain lion, catamount and panther is a large small cat native to the Americas. It inhabits North America, North, Central America, Cent ...

s (''Puma concolor'') and

wolves The wolf (''Canis lupus''; : wolves), also known as the grey wolf or gray wolf, is a canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, including the dog and dingo, though gr ...

(''Canis lupus''). Nestlings and young fox squirrels are particularly vulnerable to climbing predators such as

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...

s (''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 126 species in 18 genera. Opossums originated in South America and entered North A ...

s (''Didelphis virginiana''),

rat snake Rat snakes are members – along with kingsnakes, milk snakes, Oxybelis, vine snakes and indigo snakes – of the subfamily Colubrinae of the family Colubridae. They are medium to large Constriction, constrictors and are found throughout much o ...

s (''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.

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 {{Authority control Sciurus niger Rodents of Canada Rodents of the United States 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