Eastern fox squirrel (Sciurus niger)
|Also known as:||Bryant's fox squirrel, cat squirrel, Delmarva fox squirrel, fox squirrel, stump-eared squirrel|
|Size||Total length: 41.8 - 73.6 cm (2) (3)|
Tail length: 17.7 - 35.5 cm (3)
|Weight||453 - 1,361 g (3) (4) (5)|
- The eastern fox squirrel is very variable in colouration, ranging from reddish-brown to grey or black, often with a white nose and ears.
- The eastern fox squirrel has flexible ankle joints which allow it to rotate its feet by 180 degrees as it descends tree trunks head-first.
- The eastern fox squirrel builds large nests out of twigs and leaves, which it uses for shelter and to rear its young.
- To see it through the winter, the eastern fox squirrel buries nuts in the ground to feed on later.
The eastern fox squirrel is classified as Least Concern (LC) on the IUCN Red List (1).
The eastern fox squirrel (Sciurus niger) is a relatively large North American squirrel with a long, bushy tail and very variable colouration. Its scientific name, niger, means ‘black’ and refers to the black fur of the first individual to be described (2) (3) (4). However, the common name ‘fox squirrel’ refers to the yellowish-red, fox-like colour that is also common in this species (2) (3).
The colouration of the eastern fox squirrel varies both within and between different populations. The upperparts of the body can range from grey to buffy-grey, black or tawny brown, often with a grizzled appearance, while the underparts can be white to reddish-brown, yellowish, cinnamon or pale grey (2) (4) (5) (6). The top of the head is usually black, and some individuals have a white to creamy-white nose and ears (2) (4) (5). The eastern fox squirrel’s feet may vary from buff to whitish or orange-brown (2) (5) (6) and its tail can be pale grey (4) (5) or a mixture of black and reddish-brown, often with a buffy or tawny underside (2) (6).
The male and female eastern fox squirrel are similar in appearance (3) (4). In winter, this species is coloured similarly to in summer, but its ears may become more tufted and the soles of its feet often become densely furred (2) (3) (4). All-black (melanistic) individuals are quite common, especially in the south of the eastern fox squirrel’s range (3) (4) (5) (6).
Around ten subspecies of eastern fox squirrel have been described, which vary in their colouration and geographical distributions (2) (4) (5). Some colour forms of the eastern fox squirrel are very similar in appearance to the grey squirrel (Sciurus carolinensis), but the eastern fox squirrel can be distinguished by its larger size and generally more reddish colouration (3) (6). The eastern fox squirrel is also unique among mammals in accumulating a chemical in its teeth, bones and tissues which makes its bones pink rather than white (2) (3).
The eastern fox squirrel occurs across most of the eastern United States, as well as a few parts of southern Canada and northern Mexico (1) (4) (5). This species has also been introduced to areas outside of its native range, including parts of the western United States, such as California and Washington, as well as British Columbia and Ontario in Canada (1) (4) (5) (6).
The eastern fox squirrel typically inhabits open woodlands with scattered trees and a relatively open understorey (1) (5). It is commonly found in habitats with trees that produce nuts which can be stored over winter, such as oaks, hickories, walnuts and pines (4). The eastern fox squirrel is able to inhabit hedgerows and timbered fencerows that extend into prairies (2) (3) (5) (6) and can also be found in urban areas (3) (6).
An adept climber, the eastern fox squirrel has sharp, curved claws which give it good grip (4) (6), as well as unusually flexible ankle joints which allow it to rotate its feet by 180 degrees as it descends tree trunks head-first (6). This species is also able to hang by its hind limbs while grasping food in its front feet (2) (4), and its long tail assists with balance as it moves through the trees (6). However, although it is well adapted to life in the trees, the eastern fox squirrel also spends a considerable amount of its time on the ground (2) (3) (5) (6).
The eastern fox squirrel is active year-round and usually forages during the day. This species builds leaf nests, known as dreys, in which to shelter and to raise its young. The drey is built in a tree and consists of a large ball of leaves and shredded material on a platform of twigs, with an entrance at the side and with a lining of shredded material (2) (3) (4) (5) (6). Each squirrel may use a number of different leaf nests (2), and this species will also nest inside tree cavities, particularly in winter (2) (3) (4) (6).
The diet of the eastern fox squirrel is quite varied, but consists mostly of the nuts and seeds of trees such as oak, hickory, walnut, beech and pine. The eastern fox squirrel also consumes other seeds as well as fruits, buds, flowers, bark, twigs, sap, fungi, and crops such as corn, wheat and soybeans (4). Some animal food is occasionally taken, such as insects, birds and their eggs, and even dead fish (2) (3) (4) (5) (6). The eastern fox squirrel has also been known to gnaw on bones, antlers and turtle shells to obtain calcium and other minerals (2) (3). This species stores nuts by burying them in the ground, giving it a supply of food for the winter months. Many of these nuts are never retrieved, and can go on to sprout into new trees (2) (3) (4) (5) (6).
The eastern fox squirrel is not particularly social, although some individuals occasionally share a nest in winter (2) (3) (5). The home ranges of different individuals overlap, but females with young often defend a small core area of their range (4) (5) (6). Body and tail postures play an important role in communication in the eastern fox squirrel, as do scents and sounds (4) (6). The most common vocalisation is a series of barks (2) (4) (5) (6), while a chatter bark is given in alarm and the teeth are chattered as a sign of aggression (6).
The eastern fox squirrel usually has two main breeding periods each year, the first occurring between November and February and the second between April and July (4) (5). During these breeding periods, each female is receptive for less than one day (5) (6), and noisy chases take place as dominant males pursue females with which to mate (2) (3). The female eastern fox squirrel usually gives birth to 2 or 3 young after a gestation period of 44 to 45 days (3) (4) (5) (6), although up to 7 young are sometimes born (5) (6).
The young eastern fox squirrels are naked at birth, with their eyes and ears closed. Their fur begins to grow after about a week, but their eyes do not open until they are about five weeks old (2) (3) (4) (6). The young squirrels first leave the nest at 7 to 8 weeks old, but are not fully weaned until they are about 12 weeks old (2) (4) (5). Some female eastern fox squirrels can raise two litters of young each year (2) (5), with the young from the second litter occasionally staying in the nest with the female for their first winter (3) (6).
Male eastern fox squirrels reach sexual maturity at about 10 to 11 months old (3) (4). Females have been known to give birth as early as eight months old, but most do not breed until the year following their birth (2) (4) (5). The eastern fox squirrel is hunted by a variety of predators, including bobcats, foxes, coyotes, raccoons, hawks, owls and snakes (2) (3) (4) (5) (6), but individuals that survive can potentially live for up to 13 years in the wild, with females tending to live longer than males (4) (5) (6).
The eastern fox squirrel is a widespread and abundant species and is not currently considered to be threatened (1). In some regions, such as in Canada, the eastern fox squirrel is expanding its range thanks to human activities such as corn farming, which helps to create suitable habitat (6).
However, although this common squirrel is not globally threatened, some local populations are declining due to habitat loss (1) (5). For example, heavy logging of pine forests, together with rapid urbanisation and development, threatens eastern fox squirrels in parts of Florida. The prevention of fires can also result in increased growth of understorey vegetation, making habitats less suitable for this species (7). In addition, the eastern fox squirrel is a popular game animal throughout the United States and is often heavily hunted (2) (3) (5).
Of particular concern are the subspecies Sciurus niger avicennia, Sciurus niger cinereus, Sciurus niger niger and Sciurus niger shermani, which have fairly small ranges and are threatened by habitat loss (2) (4) (5) (7). The subspecies S. c. cinereus, known as the Delmarva fox squirrel, is federally listed as ‘Endangered’ in the United States (8). The range of this subspecies has been reduced by 90 percent due to rapid habitat loss within the Delmarva Peninsula, on the east coast of the United States (7) (8) (9).
The eastern fox squirrel occurs in many protected areas across its large range (1). The threatened subspecies S. c. cinereus and S. c. avicennia also occur in a number of reserves (7) (8), and S. c. cinereus has been translocated to a number of new locations to increase its population size and range (7) (8) (9).
Recommended conservation measures for threatened populations of the eastern fox squirrel include protecting their habitats by establishing and properly managing large reserves, and ensuring that mature trees which provide food and nesting holes are preserved (3) (7).
Find out more about the eastern fox squirrel and other squirrel species:
Koprowski, J.L. (1994) Sciurus niger. Mammalian Species, 479: 1-9. Available at:
BBC Nature - Squirrels:
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- Gestation: the state of being pregnant; the period from conception to birth.
- Home range: the area occupied by an animal during routine activities, which is not actively defended.
- Melanism: in animals, the condition of having darkened skin, hair or feathers due to excessive production of the pigment melanin, usually resulting in the animal being entirely black.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
- Translocated: when individual living organisms from one area have been transferred and released or planted in another area.
IUCN Red List (September, 2013)
- Whitaker Jr, J.O. and Hamilton Jr, W.J. (1998) Mammals of the Eastern United States. Cornell University Press, Ithaca, New York.
- Schwartz, C.W. and Schwartz, E.R. (2001) The Wild Mammals of Missouri. Second Revised Edition. University of Missouri Press, Columbia, Missouri.
Koprowski, J.L. (1994) Sciurus niger. Mammalian Species, 479: 1-9. Available at:
- Thorington Jr, R.W., Koprowski, J.L., Steele, M.A. and Whatton, J.F. (2012) Squirrels of the World. Johns Hopkins University Press, Baltimore.
- Naughton, D. (2012) The Natural History of Canadian Mammals. University of Toronto Press, Toronto.
Hafner, D.J., Yensen, E. and Kirkland Jr, G.L. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
U.S. Fish and Wildlife Service: Species Profile - Delmarva Peninsula fox squirrel (Sciurus niger cinereus) (September, 2013)
- Lance, S.L., Maldonado, J.E., Bocetti, C.I., Pattee, O.H., Ballou, J.D. and Fleischer, R.C. (2003) Genetic variation in natural and translocated populations of the endangered Delmarva fox squirrel (Sciurus niger cinereus). Conservation Genetics, 4: 707-718.