Fox squirrel
The fox squirrel, also known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to North America. It is sometimes mistaken for the American red squirrel or eastern gray squirrel in areas where the species coexist, though they differ in size and coloration.The word Sciurus came from the ancient Greek words, ‘skia’ meaning shade and ‘oura’ meaning tail. Niger refers to the black coloration.
Description
The fox squirrel's total length measures, with a body length of and a similar tail length. They range in weight from.The length of its hind foot is 5.1 to 8.2 cm. There is no sexual dimorphism 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, 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 and Iowa along the Missouri River, there are populations with uniform black coats.File:Fox Squirrel in Central Florida.jpg|thumb|left|Black morph from central Florida
To help with climbing, the squirrels have sharp claws, developed extensors 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.
Distribution and habitat
The fox squirrel's natural range extends through most of the eastern United States, north into the southern prairie provinces of Canada, west to the Dakotas, Colorado, and Texas, and south to the northern parts of Coahuila, Nuevo León and Tamaulipas. It is absent in New England, New Jersey, most of New York, northern and eastern Pennsylvania, Ontario, Quebec, and the Atlantic provinces of Canada. It has 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 among oak, hickory, walnut, pecan and pine trees, storing their nuts for winter. Western range extensions in Great Plains regions such as Kansas are associated with riverine corridors of cottonwood. Some subspecies native to several eastern U.S. states are the Delmarva Peninsula fox squirrel, and the southern fox squirrel.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 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 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. Leaf nests are built during the summer months in forks of deciduous trees about 30 feet above the ground. Fox squirrels use natural cavities and crotches as tree dens. Den trees in Ohio had an average diameter at breast height 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 flickers or red-headed woodpeckers. 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.
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, S. niger has been included since 2016 in the list of Invasive Alien Species of Union concern. This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.Introduction to California
Eastern fox squirrels have been intentionally introduced from portions of their native range to many urban and suburban areas within the western United States, including areas within California, Idaho, Montana, Oregon and Washington. For example, eastern fox squirrels were introduced in California to the city of Fresno from Missouri in 1900 or 1901, to the Veterans Hospital in West Los Angeles in 1904 from some region of the Mississippi Valley, to the area around the San Diego Zoo in 1920, to the campus of the University of California, Berkeley circa 1926, to Mount Diablo in Clayton in 1960 and to Bakersfield from Fresno in 1985.Behavior and ecology
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 "dreys", 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. In general, fox squirrel foods include mast, tree buds, insects, tubers, bulbs, roots, bird eggs, pine nuts and spring-fruiting trees, and fungi. Agricultural crops such as corn, soybeans, oats, wheat, and fruit are also eaten. Mast eaten by fox squirrels commonly includes turkey oak, southern red oak, blackjack oak, bluejack oak, post oak, and live oak.In Illinois, fox squirrels rely heavily on hickories from late August through September. Pecans, black walnuts, osage orange 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 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 and honey locust, corn, wheat, eastern cottonwood bark, ash seeds, and eastern red cedar 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, blackberries, 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 acorns, black oak acorns, red oak acorns, walnuts, and corn.
In eastern Texas, fox squirrels prefer the acorns of bluejack oak, pecans, southern red oak, and overcup oak. The least preferred foods are acorns of swamp chestnut oak and overcup oak. In California, fox squirrels feed on English walnuts, 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, silver maple, and elms. Summer foods include a variety of berries, plum and cherry pits, fruits of basswood, fruits of box elder, black oak acorns, hickory nuts, seeds of sugar and black maple, grains, insects, and unripe corn. Autumn foods consist mainly of acorns, hickory nuts, beechnuts, walnuts, butternuts, and hazelnuts. Caches of acorns and hickory nuts are heavily used in winter.