EASTERN FOX SQUIRREL
Sciurus niger Linnaeus 1758

Order Rodentia : Family Sciuridae

DESCRIPTION. A large tree squirrel with rusty or reddish underparts and brownish or grayish upperparts; tail usually less than half of total length and cinnamon, mixed with black, in color; feet cinnamon. Dental formula: I 1/1, C 0/0, Pm 1/1, M 3/3 × 2 = 20. Averages for external measurements: total length, 522 mm; tail, 245 mm; hind foot, 72 mm. Weight, 600–1,300 g.

DISTRIBUTION. Occurs in suitable habitats in eastern four-fifths of state. Range has been expanded westward by introductions and the spread of pecan orchards. For example, 30 eastern fox squirrels were trapped at Amarillo in about 1987 and released into the city park in Brownfield, Terry County, where they have subsequently spread across the city in tree-lined residential areas.

SUBSPECIES. Sciurus n. limitis in most of the western part of the range in the state, S. n. ludovicianus in the east, and S. n. rufiventer in the Canadian River drainage and adjacent areas of northwestern and extreme north-central Texas.

HABITS. Fox squirrels are adaptable to a wide variety of forest habitats, but in most areas, open woodlands of mixed trees and bottomland riparian areas along streams and rivers support the heaviest populations. The best habitat is mature oak–hickory woodland broken into small, irregularly shaped tracts of 2–8 ha (5–20 acres) and connected by strips of woodland that serve as corridors. Intermixture of pine, elm, beech, pecan, maple, and other food-producing trees adds to the attractiveness of the habitat. Along the western parts of their range, eastern fox squirrels are restricted more or less to river valleys that support pecans, walnuts, oaks, and other required trees. Motts of live oak and other tree species in the valleys of the Edwards Plateau are favored habitats.

Where hollow trees are available they are preferred as den sites and nurseries; if they are unavailable, the squirrels build outside leaf nests. These are composed of twigs and leaves, usually cut from the tree in which the nest is placed and fashioned into roughly globular structures 30–50 cm in diameter surrounding an inner cavity 15–20 cm in diameter.

A fox squirrel occupies an area of at least 4 ha (10 acres) in extent in any one season, but during an entire year >16 ha (>40 acres) may be utilized. Ranges of different fox squirrels overlap, and the animals are somewhat communal in their use of nests and probably also of winter food stores. The average carrying capacity of good, unimproved fox squirrel habitat is about one squirrel to 1 ha.

Acorns and other nuts are the natural diet of fox squirrels, although they are most important in fall and winter. Spring and summer foods consist of leftover mast, insects, green shoots, fruits, and seeds of such trees as elm and maple. Nuts are eaten from the time they start to develop and are buried in the fall in individual caches at the surface of the ground for winter use. The squirrels can relocate them by smell. Buds of many trees and fruits of osage orange add to the winter diet. Sciurus niger feeds on a wider variety of items than does the S. carolinensis. Water needs are met by consumption of succulent food materials, but during periods of drought an adequate water supply is essential.

Mating occurs principally in two periods, January and February and again in May and June; the first period is most important. Old females usually breed twice a year and yearlings but once. The average female produces only four offspring each year. The gestation period is probably about 6 or 7 weeks, as in the gray squirrel. At birth, the young are blind, nearly naked, and helpless. They develop rather slowly; their eyes open in the fifth week. They begin to climb about in the nest tree at the age of 7 or 8 weeks and to venture onto the ground at about 10 weeks. At the age of 3 months, they begin to lead a more or less independent existence. Sexual maturity is reached at the age of 10–11 months.

Historically, eastern fox squirrels were important small game animals throughout most of their range, thereby constituting a decided economic value. Fondness for agricultural crops (e.g., corn, pecans, and fruits) often brings fox squirrels into conflict with farmers and urban homeowners. As with gray squirrels, they have been documented to cause power outages by chewing through electric lines.

There is evidence to suggest that eastern fox squirrels may be increasing in abundance at the expense of eastern gray squirrels. The drainage of lowland bottomlands seems to result in a reduction in the number of gray squirrels and an increase in the number of fox squirrels.

POPULATION STATUS. Common. Eastern fox squirrels are common throughout their range in Texas.

CONSERVATION STATUS. The IUCN recognizes the eastern fox squirrel as a species of least concern, and it does not appear on the federal or state lists of concerned species. They do not appear to face any serious problems.

From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.