Sherman's Fox Squirrel
Sciurus niger shermani
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Sherman's Fox Squirrel at White Oak Plantation
Distribution:
Fox squirrels are found throughout the Eastern United States; their natural range extends from Florida north to Canada, and west to the Dakotas, Colorado, and Texas. Fox squirrels are not found in the New England region of the United States. The habitat requirements and physical characteristics of the squirrels varies signifiicantly from one part of its geographic range to another.
Fox squirrels are the largest species of tree squirrel. They exhibit distinct color phases which may be different in the different parts of their geographic distribution. In the northeastern part of their range they have gray backs with yellowish bellies, in the western part of their range they are reddish in color and in the south they may vary in color from black to almost white with a black blaze on the head and a white tipped tail. However, the subspecies is also characterized by color variability. Sherman's fox squirrel may be very light tan to nearly black and some individuals exhibit a reddish coloration. The black head is typical of Sherman's fox squirrel in Florida. There is no real difference between male and female species with respect to size or coloration.
Fox squirrels generaly live to 7 or 8 years of age. Fox squirrels from the Southeastern U. S. tend to be larger than the northern subspecies; this is the reverse of Bergmann's rule which states that animals in colder climates tend to exhibit larger body sizes. The bodies of fox squirrels generally measure 450-700 mm in overall length, 200-330 mm in tail length, 51-82 mm of right hind foot length, and their weight usually ranges from 500-1000 grams. However, larger individuals have been documented from the White Oak Plantation study areas exhibiting a maximum weight of 1350 gr. in specimens measured to date.
Reproduction:
Fox squirrels generally have two breeding seasons per year. Most breeding
occurs in December through February and May through June of each year. Females can have
two litters per year; one during each breeding season. Average litter sizes range from 2-4
individuals; the winter litter is generally smaller than the summer litter.
Habitats:
Fox squirrels are most commonly found in oak-hickory forests in the northern
parts of their range. In the south they are found in longleaf pine-turkey oak associations
and other mixed forests, including cypress and mangrove swamps. Naturally-occuring fires
are an important physical component of the habitat of fox squirrels and many other species
in the Southeastern U. S. The efforts to prevent unwanted fires in areas heavily populated
by humans in recent decades have removed this physical factor from these areas. Fires
favor longleaf pines and suppress populations of oak, hickory and other hardwood trees.
Fire also burns underbrush and ground layer species and rapidly turns over nutrients in
standing dead biomass. The result of frequent natural fires (or controlled burns) in the
Southeastern U. S. is habitat occupied by stands of longleaf pine with scattered hardwood
species and an open understory.
The longleaf pine survive the fires and live to maturity and beyond. The thick bark, the long needles and the growth pattern of this species enhance its survivorship in these fires. Sections of the thick bark actually pop off the tree as it burns carrying the heat away from the tree. The long needles protect the meristematic area of the seedling from the damaging effects of the fire. The tree seedling remains in the "grass" stage while a root system is developed and then grows rapidly to a meter or so in height to reduce the period of time that the meristematic area is exposed to the hottest part of any fire that may occur. These mature longleaf pines are another important habitat component for Sherman's fox squirrel.
Fox squirrels typically use 3 different types of nests: winter (primary) dreys , summer (secondary) dreys, and dens. At White Oak Plantation the primary (winter) dreys are constructed of mostly longleaf pine needles in the longleaf pine-hardwood associations and are usually located high up in a longleaf pine tree. These nests are usually large, elaborate structures which form protective barriers against wind, temperature and precipitation. These conspicuous dreys are routinely observed at the study areas at White Oak Plantation. Secondary dreys are round conspicuous twig and leaf nests between 25 and 45 cm in diameter and are often built in hardwood trees. They are waterproof and made of an outer layer of interwoven twigs with a softer inner lining consisting of moss, bark, leaves, fur, feathers, lichen or other similar material. Secondary (summer) dreys have been noted at the White Oak Plantation study areas and these may be no more than stick platforms in hardwood trees. Secondary dreys are always less elaborate than primary dreys and may be built on exposed branches.
Fox squirrels often travel through the tree canopy and may move great distances from tree to tree without coming to the ground. Thus, trees widely separated from other trees may restrict movements of these animals and are thus less favored than trees with close neighbors.
Tree dens are another type of nest used by fox squirrels, especially in cooler parts of their geographic distribution. These are cavities lined with soft material in the main trunks of trees. Den cavities are more common in deciduous trees than in coniferous trees. Fox squirrels may use dens more often than leaf nests in winter months and secondary dreys more often in summer months in the colder climates. No tree dens have been discovered at White Oak Plantation.
Katie Petrinec, Dept. of Biology and Marine Science, Jacksonville University, designed this web page.
Updated by Dr. Ken Hoover, Professor of Biology, Jacksonville University, October 1999.