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Overview

Brief Summary

Description

"Eastern Fox Squirrels have long, foxtail-like tails, which they flick when they are excited. They and Eastern Gray Squirrels are alike in many ways. They breed at the same time of year, nest in the same kind of places, and eat the same foods. However, Fox Squirrels prefer more open habitat, whereas Grays prefer good tree cover. Fox Squirrels spend more time foraging and running about on the ground than do the grays, and may be encountered in fields quite far from any trees, where gray squirrel would not stray. Both species feed on acorns, which are rich in tannins. Tannins are poisonous to many animals, including worms, and keep the squirrels free of roundworms and tapeworms. Fox Squirrels accumulate another chemical compound, porphyrin, in their bones and teeth, which makes their bones and teeth pink and bright red under ultraviolet light. Here's a mystery: Gray Squirrels eat the same foods and this does not happen to them—nor to any other healthy mammal."

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  • Original description: Linnaeus, C., 1758.  Systema Naturae per regna tria naturae, secundum classis, ordines, genera, species cum characteribus, differentiis, synonymis, locis, p. 64.  Tenth Edition, Vol. 1. Laurentii Salvii, Stockholm, 1(2):1-824.
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Distribution

Fox squirrels are found throughout the eastern and central United States, south into northern Mexico, and north into Canada. They have been introduced into urban areas in western North America as well.

Biogeographic Regions: nearctic (Native )

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Range Description

This species is native throughout much of the eastern United States and very limited areas of adjoining Canada (extreme southern prairie provinces) and Mexico (occurs along the Rio Grande and its tributaries in northeastern Coahuila y Nuevo Leon (Ceballos and Oliva 2005)). It has been introduced to several western U.S. states and two Canadian provinces (British Columbia and Ontario).
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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Most of the eastern and central United States and adjacent south-central Canada; New York to Florida, west along major river systems to New Mexico and Colorado (Geluso 2004), Wyoming, and Montana. Introduced and established in many areas in western North America and on Pelee Island, Ontario, Canada.

Weigl et al. (1989) recognized three morphologically and ecologically different but intergrading groups of fox squirrels (see also Williams 1977, Sherman et al. 1984). One group ("eastern fox squirrel") includes populations along the Coastal Plain from the Delmarva Peninsula to Central Florida and west to the eastern edge of the Mississippi River flood plain (Weigl et al. 1989), including subspecies NIGER, CINEREUS, BACHMANI, and SHERMANI as mapped by Hall (1981). A second group ("western fox squirrel") ranges from the valleys of south-central Pennsylvania, the Appalachian mountains, and the uplands of the Gulf states west to the prairie (Weigl et al. 1989). A third "group" is an artificial one, including two isolated forms restricted to trophically poor, wetter areas in southern Florida (S. N. AVICENNIA) and the Mississippi flood plain (S. N. SUBAURATUS).

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Geographic Range

Fox squirrels are found throughout the eastern and central United States. They occur as far south as northeastern Mexico and as far north as south central Canada. They have been introduced into cities in the western United States as well.

Biogeographic Regions: nearctic (Native )

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Eastern fox squirrels occur along the Atlantic and Gulf coastal plains
from the Delmarva Peninsula in Maryland south to central Florida and
west to the Mississippi River floodplain [23]. Delmarva fox squirrels
occur in only four Eastern Shore counties in Maryland and one location
in Accomac County, Virginia. This subspecies was formerly found in
southeastern Pennsylvania, Delaware, New Jersey, and probably the
Virginia portion of the Delmarva Peninsula [2]. S. n. ssp. avicennia
occurs in southern Florida; S. n. ssp. subauratus occurs on the
Mississippi River floodplain [23].

The range of mid-western fox squirrels extends from the valleys of
south-central Pennsylvania south through the Appalachian Mountains and
the uplands of the Gulf States and west to the prairies and more
recently to the front range of the Rocky Mountains [23]. Mid-western fox
squirrels have also extended their range into northern Michigan and
westward to North Dakota, eastern Colorado, and Texas. In northern
Mexico, fox squirrels occur in the states of Coahuila, Nuevo Leon, and
Tamaulipas [16].

Eastern fox squirrels have been introduced into many portions of the West.
Introduced populations exist in California, Oregon, Washington, Idaho,
and Montana [1,5,12,16].
  • 1. 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. 11 p. [21083]
  • 2. U.S. Department of the Interior, Fish and Wildlife Service. 1979. Restoration of Demarva fox squirrel planned. Endangered Species Technical Bulletin. 4(12): 6. [25176]
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 12. Knapp, Stephen J.; Swenson, Jon E. 1986. New range records for the fox squirrel in the Yellowstone River drainage, Montana. Prairie Naturalist. 18(2): 128. [26450]
  • 16. MacClintock, Dorcas. 1970. Squirrels of North America. New York: Litton Educational Publishing, Inc. 184 p. [21087]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]

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Regional Distribution in the Western United States

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
8 Northern Rocky Mountains
11 Southern Rocky Mountains
13 Rocky Mountain Piedmont
14 Great Plains
16 Upper Missouri Basin and Broken Lands

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Physical Description

Morphology

Fox squirrels are a medium-sized tree squirrel with no sexual dimorphism. The dorsal pelage is buff to orange and the venter is rufous. Some varieties in the southeastern United States are black. These squirrels have 8 mammae. Tail is well furred. Ear tufts often develop in winter.

Adaptations for climbing include sharp recurved claws, well developed extensors of digits and flexors of forearms, and abdominal musculature.

Range mass: 696.0 to 1233.0 g.

Average mass: 800.0 g.

Range length: 454.0 to 698.0 mm.

Average length: 595.0 mm.

Sexual Dimorphism: sexes alike

Other Physical Features: endothermic ; bilateral symmetry

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Physical Description

Fox squirrels are medium-sized tree squirrels with a long, furry tail. Fur color varies greatly in this species, from overall pale grey to black with white feet. The most common fur color is reddish-brown. Often the hairs are reddish tipped with brown, giving these squirrels a frosted look. The fur on their belly is always lighter in color.

Fox squirrels have very sharp claws and muscular bodies. This enables them to climb trees and other objects extremely well.

Range mass: 696.0 to 1233.0 g.

Average mass: 800.0 g.

Range length: 454.0 to 698.0 mm.

Average length: 595.0 mm.

Sexual Dimorphism: sexes alike

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Size

Length: 70 cm

Weight: 1062 grams

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Size in North America

Sexual Dimorphism: None

Length:
Average: 595 mm
Range: 454-698 mm

Weight:
Average: 800 g
Range: 696-1,233 g
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Diagnostic Description

Larger than SCIURUS CAROLINENSIS, in which adults are 383-525 mm in total length and 340-700 g; also, NIGER has four cheek teeth on each side of the upper jaw (CAROLINENSIS usually has five), and in NIGER the tail hairs generally are not tipped with white (Flyger and Gates 1982).

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Ecology

Habitat

Fox squirrels, like other tree squirrels, use trees for escaping from predators. They are fast and agile in the trees. They can readily escape predators on the ground and large birds of prey if they can seek refuge in the trees.

Fox squirrels are found in a diverse array of deciduous and mixed forest. Areas with a good variety of tree species are preferred due to variability in mast production.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest

Other Habitat Features: urban ; suburban ; riparian

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Habitat and Ecology

Habitat and Ecology
This species prefers open woodland habitats, with scattered trees and open understory.

Systems
  • Terrestrial
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Comments: Often in open mixed hardwood forest or mixed pine-hardwood associations, but has adapted well to disturbed areas, hedgerows, and city parks. Prefer savannas or open woodlands to dense forests (Flyger in Wilson and Ruff 1999). In Michigan, four favorite habitats in descending order: oak-hickory woodlands, beech-basswood-maple, scrub oak, and floodplains (Allen 1943). In the southeastern U.S., prinicipal habitat is mature open forests of longleaf pine and turkey oak with an open understory; adjacent bottomland hardwood forests may be occupied in summer and during periods of drought (see Handley 1991). Western range extensions are associated with riparian corridors of cottonwoods and fencerows of osage orange. Dens are in tree hollows (preferred) or leaf nests (especially in mild weather). Young are born in a tree cavity or leaf nest; tree hollows are preferred for rearing young. Individuals use up to about nine nests annually.

A few particular plant communities of the Coastal Plain appear to be important in maintaining fox squirrel populations there. The structure, age, diversity, and extent of these communities within the overall pine-oak forest provide an array of often subtle requirements for the success of the squirrel in the Southeast (Weigl et al. 1989).

In Florida and North Carolina, habitats are primarily longleaf pine (PINUS PALUSTRIS)-turkey oak (QUERCUS LAEVIS) sandhills characterized by large, well-spaced pines and an understory of scattered or clumped oaks (Moore 1953, Kantola 1986, Weigl et al. 1989, Cox 1990), although squirrels may also be found in other open pine stands, mixed pine-hardwood forests, and in ecotones between forest types. Habitat structure, specifically the size and spacing of pine and oak trees, appears to be more important than the actual species composition of the habitat (Taylor 1973, Hilliard 1979, Weigl et al. 1989). Only stands with large mature trees appear to supply adequate supplies of food and nesting sites. The large size of the eastern fox squirrel appears to adapt it to the openness of the pine-oak forest and the arrangements of habitats within the Coastal Plain. Large size is advantageous in handling the large cones of longleaf pine and in traveling along the ground between widely spaced trees, food sources, and blocks of habitat (Weigl et al. 1989).

Use of edge habitats by fox squirrels is repeatedly mentioned in the literature (Smith and Follmer 1972, Flyger and Smith 1980, Nixon et al. 1984, Kantola 1986, Weigl et al. 1989, Cox 1990). While fox squirrels in North Carolina Sandhills used pine-oak forest at least 80 percent of the time, there was marked seasonality in habitat use. During the winter months, fox squirrel activity was significantly higher in edge habitats and in bottomland forest, while in the summer months activity shifted from open pinelands and sand ridges toward moister lowlands (Weigl et al. 1989). Based on a one-year study of Florida fox squirrels, Kantola and Humphrey (1990) suggested that the best habitats may be the edges between longleaf pine savanna and live oak (QUERCUS VIRGINIANA) forest where the availability of oak mast may be most dependable from year to year.

Weigl et al. (1989) showed that fox squirrels chose nest sites surrounded by vegetation typical of longleaf pine-turkey oak forest (Wells and Shunk 1931, Braun 1964, Waggoner 1975, Christensen 1988). Fox squirrels nested in areas characterized by open, low diversity, mature forest with little understory and xeric conditions. This contrasted markedly with conditions typical of gray squirrel nest sites, which generally were in areas of closed-canopy, high diversity, dense understory, and generally mesic conditions.

Nests are of critical importance to the survival of fox squirrels throughout their range, and nest selection and use by eastern fox squirrels has received considerable attention (Moore 1957, Hilliard 1979, Flyger and Smith 1980, Weigl et al. 1989, Kantola and Humphrey 1990). Tree hollows are particularly important in rearing young and for protection from severe weather for all tree squirrels.

Fox squirrels in the southeastern U.S. often use hardwood cavities in deciduous forest, bottomlands, and mixed forests, despite the fact that the majority of foraging takes place in pine-dominated stands. Kantola and Humphrey (1990) also reported higher nest use in lower slope situations than on drier sandhill areas. Suitable hollows are fairly scarce in pine-oak forests, primarily owing to timber management practices, firewood cutting, and oak suppression (Weigl et al. 1989; Weigl, pers. comm.), but are more abundant in adjacent more mesic habitats.

Leaf nests are frequently used during warmer months and in the more southern portions of the squirrels' range. Use of leaf nests in North Carolina was associated with periods of mild weather and/or abundant food, and Weigl et al. (1989) found that nest selection during the warmest periods occurred most often in moister habitats and wetland edges. In Florida, tree cavity nests were rarely used even when abundant, comprising only 7.4% of all nest locations recorded (Kantola and Humphrey 1990).

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Fox squirrels prefer open, savannah-like habitats, where trees are widely spaced and the understory is open. They are most common in oak-hickory forests but are also found in live oak, mixed forests, cypress and mangrove swamps, and pine forests. Because of this habitat preference they tend to do well in urban and suburban settings. They are rare in heavily forested areas, unlike their close relatives Sciurus carolinensis.

Fox squirrels need large trees with cavities or holes in them for building nests to raise their young. They may use these cavities to hibernate in during the winter as well. They also build leaf nests, a collection of leaves in the branches that are used by adults. They build the leaf nests high up in larger trees. They usually use large oak, elm, and other hardwood trees.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest

Other Habitat Features: urban ; suburban ; riparian

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Cover Requirements

More info for the terms: cover, tree

Eastern fox squirrels use leaf nests or tree cavities for shelter and litter
rearing [1]. 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 15
inches (38.1 cm) or more generally provide adequate cover and
reproductive habitat. Optimum tree canopy closure for eastern fox squirrels is
from 20 to 60 percent. Optimum conditions understory closure occur when
the shrub-crown closure is 30 percent or less [1].
  • 1. 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. 11 p. [21083]

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Preferred Habitat

More info for the terms: natural, tree

Eastern 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 [1,9]. The size and spacing of pines and oaks
are among the important features of eastern fox squirrel habitat. The actual
species of pines and oaks themselves may not always be a major
consideration in defining eastern fox squirrel habitat [23]. Eastern fox squirrels are
often observed foraging on the ground several hundred meters from the
nearest woodlot. Eastern fox squirrels also commonly occupy forest edge habitat
[6].

In general, the woodland habitats occupied by the Delmarva fox squirrel
are similar to those occupied by other subspecies of eastern fox squirrels [6].
The Delmarva fox squirrel habitat consists primarily of relatively small
stands of mature mixed hardwoods and pines that have relatively closed
canopies, open understories, and a high proportion of forest edge.
Occupied areas include both groves of trees along streams and bays and
small woodlots near agricultural fields. In some areas, particularly in
southern Dorchester County, Maryland, occupied habitat includes areas
dominated by mature loblolly pine located adjacent to marshes and tidal
streams.

Nest - Eastern 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 [3,16]. Leaf nests are built during the summer months in
forks of deciduous trees about 30 feet (9 m) above the ground. Eastern fox
squirrels use natural cavities and crotches (forked branches of a tree)
as tree dens [3]. Den trees in Ohio had an average d.b.h. of 21.2
inches (53 cm) and were an average of 58.6 yards (52.7 m) from the
nearest woodland border. Eighty-eight percent of den trees in eastern
Texas had an average d.b.h. of 12 inches (30 cm) or more [1]. Dens are
usually 6 inches (15.2 cm) wide and 14 to 16 (35-41 cm) inches deep.
Den openings are generally circular and about 2.9 to 3.7 inches (7.3-9.4
cm). Eastern 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 (Colaptes auratus) or redheaded
woodpeckers (Melanerpes erythrocephalus). Crow nests have also been
used by eastern fox squirrels [16].
  • 1. 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. 11 p. [21083]
  • 3. Banfield, A. W. F. 1974. The mammals of Canada. Toronto, ON: University of Toronto Press. 438 p. [21084]
  • 6. Dueser, Raymond D.; Dooley, James L., Jr.; Taylor, Gary J. 1988. Habitat structure, forest composition and landscape dimensions as components of habitat suitability for the Delmarva fox squirrel. In: Management of amphibians, reptiles, and small mammals in North America: Proceedings of the symposium; 1988 July 19-21; Flagstaff, AZ. Gen. Tech. Rep. RM-166. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 414-421. [21086]
  • 9. Gilley, Susan. 1982. The non-game update: the Delmarva fox squirrel; making a comeback?. Virginia Wildlife. 43(12): 24-25. [3463]
  • 16. MacClintock, Dorcas. 1970. Squirrels of North America. New York: Litton Educational Publishing, Inc. 184 p. [21087]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]

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Associated Plant Communities

More info for the term: hardwood

Eastern fox squirrels inhabit a variety of open hardwood, hardwood-pine, and
swamp communities depending on geographic location. The Delmarva fox
squirrel in Maryland prefers mature stands of hardwoods such as oaks
(Quercus spp.), hickories (Carya spp.), walnuts (Juglans spp.), and
beech (Fagus spp.) that are interspersed with mature loblolly pine
(Pinus taeda). Delmarva fox squirrels are also found in deciduous
swamps close to pine woodlands [2,5,9]. In southern Florida, fox
squirrels occupy pine hammocks and range into mangrove (Rhizophora spp.)
and cypress (Cupressus spp.) stands. In coastal regions of northern
Florida, Georgia, and the Carolinas, eastern fox squirrels are most often found
in longleaf pine (Pinus palustris)/turkey oak (Quercus laevis) habitats
[5]. In Alabama, eastern fox squirrels occur along watercourses, on the shores
of bayous and in deep bald cypress (Taxodium distichum) swamps, and in
upland dry pine stands [5].

In eastern Texas, eastern fox squirrels inhabit oak-hickory ridges. Farther
west, they occupy both timbered river bottoms and oak ridges. In the
central portions of Oklahoma and Iowa, easter4n fox squirrels are most abundant
in the transition belt between prairie and oak woodland. Here, eastern fox
squirrels also occupy upland hardwood forests, dense timber along
streams and rivers, and open pecan (Carya pecan) orchards [5]. Primary
eastern fox squirrel habitat in Wisconsin is oak-hickory woodlots with oak,
swamp hardwoods, and mixed upland hardwoods [5].
  • 2. U.S. Department of the Interior, Fish and Wildlife Service. 1979. Restoration of Demarva fox squirrel planned. Endangered Species Technical Bulletin. 4(12): 6. [25176]
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 9. Gilley, Susan. 1982. The non-game update: the Delmarva fox squirrel; making a comeback?. Virginia Wildlife. 43(12): 24-25. [3463]

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Habitat: Cover Types

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the terms: hardwood, swamp

14 Northern pin oak
16 Aspen
17 Pin cherry
18 Paper birch
19 Gray birch - red maple
20 White pine - northern red oak - red maple
24 Hemlock - yellow birch
25 Sugar maple - beech - yellow birch
26 Sugar maple - basswood
27 Sugar maple
28 Black cherry - maple
39 Black ash - American elm - red maple
40 Post oak - blackjack oak
42 Bur oak
43 Bear oak
44 Chestnut oak
51 White pine - chestnut oak
52 White oak - black oak - northern red oak
53 White oak
55 Northern red oak
59 Yellow-poplar - white oak - northern red oak
60 Beech - sugar maple
61 River birch - sycamore
62 Silver maple - American elm
65 Pin oak - sweetgum
71 Longleaf pine - scrub oak
70 Longleaf pine
76 Shortleaf pine - oak
78 Virginia pine - oak
80 Loblolly pine - shortleaf pine
81 Loblolly pine
82 Loblolly pine - hardwood
85 Slash pine - hardwood
87 Sweet gum - yellow-poplar
88 Willow oak - water oak - diamondleaf oak
89 Live oak
91 Swamp chestnut oak - cherrybark oak
92 Sweetgum - willow oak
93 Sugarberry - American elm - green ash
94 Sycamore - sweetgum - American elm
95 Black willow
96 Overcup oak - water hickory
100 Pondcypress
101 Baldcypress
105 Tropical hardwoods
108 Red maple
109 Hawthorn
110 Black oak
203 Balsam poplar
217 Aspen
221 Red alder
222 Black cottonwood - willow
233 Oregon white oak
235 Cottonwood - willow
236 Bur oak
241 Western live oak
246 California black oak
249 Canyon live oak
250 Blue oak - Digger pine
252 Paper birch
255 California coast live oak

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Habitat: Plant Associations

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

K025 Alder - ash forest
K026 Oregon oakwoods
K030 California oakwoods
K080 Marl - everglades
K090 Live oak - sea oats
K091 Cypress savanna
K092 Everglades
K098 Northern floodplain forest
K099 Maple - basswood forest
K100 Oak - hickory forest
K101 Elm - ash forest
K102 Beech - maple forest
K103 Mixed mesophytic forest
K104 Appalachian oak forest
K105 Mangrove
K106 Northern hardwoods
K108 Northern hardwoods - spruce forest
K110 Northeastern oak - pine forest
K111 Oak - hickory - pine forest
K112 Southern mixed forest
K113 Southern floodplain forest
K115 Sand pine scrub
K116 Subtropical pine forest

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Habitat: Ecosystem

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES10 White-red-jack pine
FRES12 Longleaf-slash pine
FRES13 Loblolly-shortleaf pine
FRES14 Oak-pine
FRES15 Oak-hickory
FRES16 Oak-gum-cypress
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES28 Western hardwoods
FRES41 Wet grasslands

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

In Ohio, individuals have been reported traveling 1.2 km between woodlots on a daily basis (Whitaker and Hamilton 1998). Other reported home ranges vary from 13 to 43 hectares (males 26 to 43 hectares) in the east (Ha 1983, Weigl et al. 1989, Hilliard 1979, Edwards 1986, Kantola 1986); and from 0.8 to 7.6 hectares in the west (Baumgartner 1943, Bernard 1972, Adams 1976, Havera and Nixon 1978).

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Trophic Strategy

A wide variety of foods are taken, ranging from vegetative matter to gall insects, moths, beetles, bird, eggs, and dead fish. Acorn, hickory, walnut, mulberry, and hawthorne seeds are preferred. Food can often become limiting in the winter, so squirrels commonly cache seeds in a scattered fashion for the colder months. Nuts are opened by a levering technique of the lowering incisors, a skill at which squirrels become proficient quickly.

Animal Foods: birds; mammals; eggs; carrion ; insects; terrestrial non-insect arthropods

Plant Foods: leaves; seeds, grains, and nuts; fruit

Other Foods: fungus

Primary Diet: omnivore

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Comments: Foraging commonly occurs on the ground. Typical foods include nuts, fungi, seeds, berries, and shoots; other food include tree buds and flowers and small amounts of insects and other animal material. In the southeastern U.S., feeds mostly on pine seeds when they are available. Scatterhoarder; food is cached in the ground in fall. Much of the literature on food habits in the Sandhills of North Carolina, was summarized by Weigl et al. (1989), as follows:

Food is generally abundant during the spring, and squirrels feed on pine buds, staminate cones, flowers, corms, bulbs, previous seasons' mast, fungi, and insects. The early summer months, however, are the period of the poorest food availability. Increasing temperature and aridity result in less succulent vegetation and fewer emerging insects. Mast from the previous fall has been exhausted, new seeds are not yet available, and fungi and soft mast resources are patchy. Late summer is again a period of food abundance and squirrel activity increases markedly. Green longleaf pine cones become a primary food source and, during years of abundant cone production, squirrels can rapidly gain weight within a relatively restricted foraging area. In more typical years, squirrels forage widely, cutting and eating cones, as well as foraging for dispersed seeds. During this season, soft mast (berries of ILEX, PERSEA, VITIS, and SMILAX), fruits, and fungi are more predictably available and readily eaten. Longleaf pine cones are a crucial food source in that they are practically the only food available until the fall mast crop. The highly nutritious seeds are critical to recovery from the early summer period of food scarcity and in preparation for winter. Because of the fox squirrel's large size, it is almost uniquely adapted to take advantage of this seasonal resource.

Moore (1957) conducted a two-year study of Sherman's fox squirrel (S. N. SHERMANI) occupying similar longleaf pine-turkey oak forests. Florida squirrels apparently do not undergo the kind of severe early summer food scarcity experienced by those in North Carolina. Weigl et al. (1989) suggested that this may account for the larger size and the higher incidence of summer litters in the Florida subspecies. Mast forms the bulk of the diet during the fall, winter, and parts of the following spring in good mast years. This is particularly true in years of poor pine cone availability. Acorns (QUERCUS LAEVIS, in particular) and hickory nuts (CARYA) may be supplemented by fungi and the seeds and drupes of other hardwoods (LIQUIDAMBAR, NYSSA, and LIRIODENDRON, among others). Pine-oak habitats typically support relatively few oak species with different fruiting phenologies (the so-called red oaks produce acorns the second fall after flowering, while the white oaks mast the first fall after flowering). Because of this low diversity and difference in phenology, a single severe spring frost can destroy the larger part of the mast crop over a two-year period. This can be disastrous for fox squirrels confined to a limited area of suitable habitat. In addition, hickory mast tends to be restricted to moister forest areas and in isolated groves where fox squirrels must compete with gray squirrels and other mast feeders. During the winter, food supplies are dependent upon the fall mast crop and can be variable from year to year. In poor mast years, fox squirrels appear to spend considerable time searching for fallen longleaf pine cones, scattered seeds, and the smaller cones of pond pine (PINUS SEROTINA), and digging for hypogeous fungi around the bases of longleaf pines. During years of poor turkey oak mast availability, fox squirrels in Florida tended to increase time spent foraging in lower-elevation live oak stands which tended to produce more predictable mast (Kantola and Humphrey 1990).

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Food Habits

Fox squirrels are omnivores, eating everything from plant matter to Insecta, Aves, and carrion. Their diet depends on what is available in the area in which they live. Fox squirrels mainly eat the nuts, flowers, and buds of oak trees and walnut, hickory, and pecan trees. They also eat fruits, seeds, and buds of maple trees, mulberry, hackberry, elms, buckeyes, horse chestnuts, wild cherries, dogwoods, hawthorn, hazelnut, ginkgo, and pine seeds. They eat edible varieties of fungus when they are available. They will eat Aves, bones, and other small animals or animal remains as they find them. Squirrels are scatterhoarders, which means that they hide small amounts of food in various locations and go back to find it later. They find them later by remembering where they put them and by smelling for the food. They use their strong incisors to chew through the husks of the different kinds of seeds they eat. In the fall of each year fox squirrels begin eating much more than they need so that they can accumulate a large store of body fat to help them get through the winter. Fox squirrels can get some of the water they need from eating moist foods, but generally need to have standing water for drinking. They might find small pools of water that collect after rains in the holes and nooks of large trees. Female fox squirrels need foods with extra protein and calcium, such as bones, meat, and nuts, when they are pregnant and nursing their young.

Animal Foods: birds; mammals; eggs; carrion ; insects; terrestrial non-insect arthropods

Plant Foods: leaves; seeds, grains, and nuts; fruit

Other Foods: fungus

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Food Habits

More info for the terms: mast, milk stage, swamp, tree

Food habits of eastern fox squirrels depend largely on geographic location [5].
In general, eastern fox squirrel foods include mast, tree buds, insects, tubers,
bulbs, roots, bird eggs, seeds of pines and spring-fruiting trees, and
fungi. Agricultural crops such as corn, soybeans, oats, wheat, and
fruit are also eaten [1,5,16,23]. Mast eaten by eastern fox squirrels
commonly includes turkey oak, southern red oak (Q. falcata), blackjack
oak (Q. marilandica), bluejack oak (Q. incana), post oak (Q.
stellata), and live oak (Q. virginiana) [23].

In Illinois, eastern fox squirrels rely heavily on hickories from late August
through September. Pecans, black walnuts (Juglans nigra), osage orange
(Maclura pomifera) 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 utilized. By early
summer, corn in the milk stage becomes a primary food [5].

During the winter in Kansas, osage orange is a staple item supplemented
with seeds of the Kentucky coffee tree (Gymnocladus dioicus) and honey
locust (Gleditsia triacanthus), corn, wheat, eastern cottonwood (Populus
deltoides var. deltoides) bark, ash seeds, and eastern redcedar
(Juniperus virginianus) berries. In the spring, eastern fox squirrels feed
primarily on buds of elm, maple, and oaks but also on newly sprouting
leaves and insect larvae [5].

Eastern 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. Eastern fox squirrels also eat buckeyes, seeds and buds of maple
and elm, hazelnuts (Corylus spp.), blackberries (Rubus 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) acorns, black oak (Q. velutina)
acorns, red oak (Q. rubra) acorns, walnuts, and corn [5].

In eastern Texas, eastern fox squirrels prefer the acorns of bluejack oak,
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, eastern fox squirrels feed on English walnuts (J.
regia), oranges, avocados, strawberries, and tomatoes. In midwinter,
they feed on eucalyptus seeds [5].

In Michigan, eastern 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), silver maple (A.
saccharinum), and elms. Summer foods include a variety of berries, plum
and cherry pits, fruits of basswood (Tilia americana), fruits of box
elder (Acer negundo), black oak acorns, hickory nuts, seeds of sugar (A.
saccharum) and black maple (A. nigrum), grains, insects, and unripe
corn. Fall foods consist mainly of acorns, hickory nuts, beechnuts,
walnuts, butternuts (J. cinerea), and hazelnuts. Caches of acorns and
hickory nuts are heavily used in winter [5].
  • 1. 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. 11 p. [21083]
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 16. MacClintock, Dorcas. 1970. Squirrels of North America. New York: Litton Educational Publishing, Inc. 184 p. [21087]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]

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Associations

Because squirrels prey so heavily on the seeds of trees they play a significant role in shaping the composition of forests. They may eat (along with other seed-eating animals) almost all of the tree seeds that trees produce in some years. When squirrels bury seeds and forget them, these seeds are likely to sprout where they were placed. Squirrels, therefore, act to promote the growth of certain kinds of trees. Fox squirrels are also important prey items for small predators because of their abundance in the environment.

Ecosystem Impact: disperses seeds

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Fox squirrels are preyed on mainly by large hawks and owls. Young squirrels may also be taken by snakes. Fox squirrels take advantage of their agility and maneuverability in the trees to escape most predators. They emit alarm calls that alert other squirrels when they see a predator.

Known Predators:

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Ecosystem Roles

Because squirrels eat so many tree seeds, they play a significant role in shaping the composition of forests. Together with other seed-eating animals, they may eat almost all of the tree seeds produced in some years. When squirrels bury seeds and forget them, these seeds are likely to sprout where they were placed. Because of this, squirrels promote the growth of certain kinds of trees. Fox squirrels are also important prey items for small predators because they are so abundant.

Ecosystem Impact: disperses seeds

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Predation

Fox squirrels are preyed on mainly by large Accipitridae and Strigiformes. Young squirrels may also be taken by Squamata. Fox squirrels take advantage of their agility and maneuverability in the trees to escape most predators. They emit alarm calls that alert other squirrels when they see a predator.

Known Predators:

  • hawks (Accipitridae)
  • owls (Strigiformes)
  • snakes (Serpentes)

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Predators

More info for the term: natural

Relatively few natural predators can regularly capture adult eastern fox
squirrels. Of these predators, most only take eastern fox squirrels
opportunistically [23]. Eastern fox squirrel predators include: bobcats (Felis
rufus), foxes (Vulpes spp. and Urocyon spp.), red-tailed hawks (Buteo
jamaicensis), red-shouldered hawks (Buteo lineatus), great-horned owls
(Bubo virginianus), barred owls (Strix varia), and dogs (Canidae)
[3,5,23]. Nestlings and young eastern fox squirrels are particularly vulnerable
to climbing predators such as raccoons (Procyon lotor), opossums
(Didelphis virginiana), rat snakes (Elaphe obsoleta), and pine snakes
(Pituophis melanoleucus) [23]. In those states where eastern fox squirrels are
not protected, they are considered a game animal [5,23]. Eastern fox squirrels
are hunted more for trophy than for food [23]. Overharvest by hunting
has been reported from small woodlots and public shooting areas in Ohio,
Michigan, and Indiana [5].
  • 3. Banfield, A. W. F. 1974. The mammals of Canada. Toronto, ON: University of Toronto Press. 438 p. [21084]
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]

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Known predators

Sciurus niger is prey of:
Strix varia
Squamata
Strigiformes
Accipitridae

Based on studies in:
USA: Illinois (Forest)

This list may not be complete but is based on published studies.
  • A. C. Twomey, The bird population of an elm-maple forest with special reference to aspection, territorialism, and coactions, Ecol. Monogr. 15(2):175-205, from p. 202 (1945).
  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
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Known prey organisms

Sciurus niger preys on:

leaves
fungi
Arthropoda
Insecta
Aves
Mammalia

Based on studies in:
USA: Illinois (Forest)

This list may not be complete but is based on published studies.
  • A. C. Twomey, The bird population of an elm-maple forest with special reference to aspection, territorialism, and coactions, Ecol. Monogr. 15(2):175-205, from p. 202 (1945).
  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

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Global Abundance

10,000 to >1,000,000 individuals

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General Ecology

Fox squirrels are largely solitary animals across their geographic range, though they may congregate briefly during the breeding season or near concentrated food supplies (Bakken 1952, Havera and Nixon 1978, Benson 1980, Armitage and Harris 1982, Brown 1984, Nixon et al. 1984, Steele et al. 1984, Weigl et al. 1989, Kantola and Humphrey 1990, Handley 1991).

Much of the demography and ecology is determined by food availability and distribution. The low diversity, open pine-oak forests favored by fox squirrels in the southeastern U.S. are typified by food resources that tend to be of low abundance and very patchy distribution.

Population density in the Coastal Plain portion of the range is relatively low. Moore (1957) and Hilliard (1979) estimated densities of 0.33/ha and 0.26/ha, respectively. Weigl et al. (1989) reported densities averaging 0.05/ha. More recent estimates for northern Florida S. N. SHERMANI averaged 0.027-0.054/ha (Kantola and Humphrey 1990). In the southeastern U.S., fox squirrels are very scarce across even in the best quality habitats. In woodlots in the Midwest, average density typically is 1-4/ha but may reach 12/ha (Weigl et al., 1989, Koprowski 1994). An average of 15 gray squirrels per hectare was reported by Gurnell (1983). Numbers may vary annually, depending on weather, food availability, and the effects of diseases and parasites (Weigl et al. 1989).

The longest reported dispersal movement is 64.4 km (Allen 1943, Baker 1983, Caire et al. 1989, Kantola and Humphrey 1990).

Average home range sizes in the Sandhills of North Carolina (26.6 ha in males, 17.2 ha in females, mean convex polygon) (Ha 1983, Weigl et al. 1989) were similar to those reported from similar habitats in Georgia (males 26.4 ha, females 13.0 ha, MCP) (Hilliard 1979), but were smaller than those for South Carolina fox squirrels using pine plantations and hardwood "runners" (males 31.6 ha, females 19.3 ha) (Edwards 1986) and for the larger S. N. SHERMANI in longleaf pine forests of Florida (males, 42.8 ha; females, 16.7 ha, harmonic mean) (Kantola 1986). These home ranges are in contrast to the much smaller ranges (0.8 to 7.0 ha, MCP) reported for western fox squirrels (Baumgartner 1943, Bernard 1972, Adams 1976, Havera and Nixon 1978). The larger ranges of fox squirrels in the southeastern U.S. are not explained solely by their larger body size and diet, and they may result from the patchiness of resources in their habitat (Weigl et al. 1989, Kantola and Humphrey 1990). Home range overlap is extensive.

Weigl et al. (1989) described an intriguing relationship among the fox squirrel, its hypogeous fungal food source, and longleaf pine regeneration. They suggested that one or more fungi readily consumed by the squirrels demonstrate mycorrhizal associations with longleaf pine and that the squirrels may be an important dispersal agent of fungal spores. The squirrels naturally forage across fairly large areas, including recently burned areas and clearcuts, perhaps playing a major role in inoculating barren soils with a mycorrhizal agent necessary for vigorous growth of longleaf pine.

Nut burial may aid reforestation.

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Habitat-related Fire Effects

More info for the terms: cover, duff, ground fire, hardwood

Fire often has a positive effect on eastern fox squirrel habitat. Fire
maintains the pine-oak habitat preferred by eastern fox squirrels and has a
direct effect on eastern fox squirrel foods. Under presettlement conditions
longleaf pine savannas (preferred eastern fox squirrel habitat) may have burned
at average intervals of 3 to 5 years, usually between April and October.
The open stands produced by fire result in better pine cone and mast
production. Pines and oaks growing in the open receive more light,
maintain more branches at lower levels, and produce heavier crops of
cones and nuts [23]. Additionally, nutrient availability and the
enhanced vigor of burned pine forest are associated with larger crops of
fungi. which are also important eastern fox squirrel foods [23]. A lush, grassy
understory maintained by fire is important as protective cover [15].

Fire has probably been a determining factor in the niche separation
between gray and eastern fox squirrels on the Coastal Plain. Both exist in
mixed pine-oak forests and feed heavily on acorns, but the more
competitive gray squirrel dominates where the overlap of oak crowns
allows tree-to-tree travel throughout the canopy. Eastern fox squirrels are
more abundant where patches of oaks comprise less than 30 percent of
pine-hardwood stands and do best in fire-type pine forests with
scattered hardwood inclusions [15]. Fire could be a deciding factor in
determining the availability of suitable habitat and resources for one or
the other species [23].

Fire can also have a negative effect on eastern fox squirrel habitat.
Low-intensity ground fire may destroy acorns in the forest duff [15].
  • 15. Landers, J. Larry. 1987. Prescribed burning for managing wildlife in southeastern pine forests. In: Dickson, James G.; Maughan, O. Eugene, eds. Managing southern forests for wildlife and fish: a proceedings; [Date of conference unknown]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]

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Timing of Major Life History Events

More info for the terms: litter, tree

Breeding season - Female eastern fox squirrels come into estrus in mid-December
or early January and again in June. Eastern fox squirrels normally produce two
litters a year [3,5]. However, yearling females may produce only one
litter, and poor food conditions may prevent some adult females from
breeding [5].

Breeding age - Females become sexually mature at 10 to 11 months of age.
They usually produce their first litter when they are 1 year old [5].

Gestation/litter size - The gestation period of eastern fox squirrels is 44 to
45 days. Earliest litters appear in late January; most births occur in
mid-March and July [5]. The average litter size is three, but litter
size can vary according to season and food conditions [5].

Development of young - Tree squirrels develop slowly compared to other
rodents. Eyes open when eastern fox squirrels are 4 to 5 weeks old, and ears
open at 6 weeks. Eastern fox squirrels are weaned between 8 and 10 weeks but
may not be self-supporting until 12 weeks [5,16]. Juveniles usually
disperse in September or October, but they may den together or with
their mother the first winter [3,22].

Longevity - Eastern fox squirrels generally live up to 6 years in the wild but
have survived 13 years in captivity [5,16].
  • 3. Banfield, A. W. F. 1974. The mammals of Canada. Toronto, ON: University of Toronto Press. 438 p. [21084]
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 16. MacClintock, Dorcas. 1970. Squirrels of North America. New York: Litton Educational Publishing, Inc. 184 p. [21087]
  • 22. Van Gelden, Richard George. 1982. Mammals of the National Parks. Baltimore, MD: Johns Hopkins University Press. 310 p. [20893]

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Life History and Behavior

Behavior

Fox squirrels have excellent vision, even in dim light. They have well-developed senses of hearing and smell. Scent marking is used to communicate among fox squirrels. They use a variety of sounds to communicate, including barks, chatters, distress screams, and high-pitched whines during mating. Fox squirrels will threaten one another by standing upright with their tail over their back and flicking it. Fox squirrels also have several sets of vibrissae, thick 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.

Perception Channels: tactile ; chemical

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Communication and Perception

Fox squirrels have excellent vision, even in dim light. They have well-developed senses of hearing and smell. Fox squirrels also have several sets of vibrissae. Vibrissae are thick 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.

Fox squirrels communicate many ways. They use a variety of sounds, including barks, chatters, distress screams, and high-pitched whines. They use scent marks. They also communicate through behavior. For example, they will threaten one another by standing upright with their tail over their back and flicking it.

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Cyclicity

Comments: Primarily diurnal; generally activity peaks in early morning and late afternoon except in winter when there may be a single midday peak (and/or early morning activity related to breeding); an additional midday peak may occur in summer. May remain in nest during severe weather.

In the southeastern U.S., activity levels are markedly lower for squirrels during periods of predictably low food availability during the summer. At these times, fox squirrels experience the greatest stress and seem to all but disappear from their ranges. They move from the drier pinelands and ridges to the edges of bottomlands and swamps, reduce activity, and probably use fat reserves (Weigl et al. 1989, Kantola and Humphrey 1990). As longleaf cones ripen, activity increases again. Highest activity and smallest area use occurs during the cone harvest of late summer and the mast harvest in the subsequent fall.

During the winter months in the southeastern U.S., food supplies are scarce and patchy. Higher thermoregulatory costs force squirrels to increase activity and expand ranges to locate food. Jodice and Humphrey (1992) suggested that Big Cypress fox squirrels (S. N. AVICENNIA) living on golf courses in southwestern Florida did not exhibit such dramatic changes in foraging and activity in response to food availability or weather. They suggested that the diet of these urban squirrels was unusual in diversity within seasons and stability among seasons, with the effect that seasonal activity patterns were probably driven instead by mating and young-rearing.

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Life Expectancy

Fox squirrels have been known to live to 18 years old in captivity. Under natural conditions the average lifespan is 8 to 18 years old, though most squirrels die before they reach adulthood.

Range lifespan

Status: captivity:
18.0 (high) years.

Average lifespan

Status: wild:
7.0 months.

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Lifespan/Longevity

Fox squirrels have been known to live to 18 years old in captivity. Under natural conditions the average lifespan is 8 to 18 years old, though most squirrels die before they reach adulthood.

Range lifespan

Status: captivity:
18.0 (high) years.

Average lifespan

Status: wild:
7.0 months.

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Lifespan, longevity, and ageing

Maximum longevity: 16 years (captivity) Observations: One wild born specimen was about 16 years of age when it died in captivity (Richard Weigl 2005).
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Reproduction

Females can mate with several males, but the males will compete with each other to determine who gets to mate first.

Mating System: polygynandrous (promiscuous)

Fox squirrels can mate any time of year; this behavior peaks in December and June. Males follow females prior to estrus, smelling the perineal region. Males aggregate in the home range of a female when she begins estrus. Dominance hierarchies form among the males to determine mating privilege. Copulation lasts less than thirty seconds, and females can mate with several males. A copulatory plug forms after mating. Gestation lasts 44-45 days. Average litter size is 2-3, but litters range between 1 and 7. Young are born naked, weighing between 13-18 g. Eyes open at week 5, and young are weaned at week 8. Sexual maturity is attained at 8 months for females, 10-11 months for males. Females can produce 2 litters in a year, although 1 is the norm.

Breeding season: Breeding occurs from December to February and May to June.

Range number of offspring: 1.0 to 6.0.

Average number of offspring: 3.0.

Average gestation period: 44.0 days.

Average time to independence: 3 months.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Average birth mass: 15 g.

Average gestation period: 44 days.

Average number of offspring: 3.

Average age at sexual or reproductive maturity (male)

Sex: male:
353 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
353 days.

Female fox squirrels care for their young in the nest for 6 weeks. When the mother leaves her young in the nest she covers them with nesting material. Young fox squirrels disperse away from their mothers range in the fall of their first year. Male fox squirrels disperse farther and may die more as a result.

Parental Investment: altricial

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Fox squirrels breed at two seasons: winter-spring (young are born January-April) and, less frequently, summer-fall (young born July-September) (Moore 1957, Lustig and Flyger 1975, Weigl et al. 1989). Mating behavior in North Carolina appears to be prevalent from December to early February and again in late July and August, with most litters in North Carolina born in late February and March (Weigl et al. 1989).

Gestation lasts 44-45 days (Moore 1957, Kantola 1986). In the southeastern U.S., most young are born in March-April; sometimes there is a smaller second peak in July-August (Weigl et al. 1989). Litter size generally averages 2-3. Mean litter sizes of 2.3 and 2.27 (Moore 1953) have been reported for Florida fox squirrels. For the southeastern U.S., Weigl et al. (1989) reported litter sizes (mean = 2.5) that equaled or were well below the lowest litter sizes reported for other sciurids. Many authors have suggested that older females may produce a second litter in good habitat. However, Weigl et al. (1989) recorded no instance of a second litter in eight years and suggested that no records of a second litter occur in the literature on fox squirrels in the southeastern U.S. Weaning occurs during the period when the young are 8-13 weeks old. In Florida, young are dependent on their mother for about 3 months. Earliest time of first breeding usually is the second calendar year. Family group may stay together until female is ready to mate again. Maximum reproductive longevity of females is about 12-13 years.

Reproductive output, including the percentage of sexually mature individuals that reproduce, increases with food abundance (Hilliard 1979, Kantola 1986, Weigl et al. 1989). Reproduction and litter size in North Carolina were significantly associated with food availability in the previous fall-winter periods. During poor mast years, juvenile survival increased, while adult condition declined, resulting in an overall negative impact on squirrel populations (Koprowski 1991). Juvenile squirrels are particularly sensitive to food shortages due to relatively low fat stores, higher metabolic demand, low experience in locating and processing scarce food, and perhaps low social rank (Koprowski 1991).

Few data exist on fox squirrel longevity. Data from midwestern fox squirrel populations suggest longevities of 13 years in captivity and six to seven years in the wild (Flyger and Gates 1982). The large size and low recruitment rates of fox squirrels in the southeastern U.S. suggest relatively long life spans (Moore 1953, Weigl et al. 1989). Weigl et al. (1989) suggested a life span of seven years in the Sandhills of North Carolina, although no data on age or survivorship have been reported.

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Females can mate with several males, but the males will compete with each other to determine who gets to mate first.

Mating System: polygynandrous (promiscuous)

Fox squirrels can mate all year long; however, most mating occurs in two mating seasons on from December to February and another from May until June. Females can begin to have babies at 6 months old and have one or two litters per year. Males can begin to mate at 10 to 11 months old. Female fox squirrels are pregnant for about 44 days. Average litter size is 3 young but it can range from 1 to 6 young per litter.

Babies are born without fur and weigh 13 to 18 g. They develop fur after 14 days old. They open their eyes at about 30 days old. They begin to explore outside of the nest after about 7 to 8 weeks. They don't travel much on their own until 3 months of age.

Breeding season: Breeding occurs from December to February and May to June.

Range number of offspring: 1.0 to 6.0.

Average number of offspring: 3.0.

Average gestation period: 44.0 days.

Average time to independence: 3 months.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 15 g.

Average gestation period: 44 days.

Average number of offspring: 3.

Average age at sexual or reproductive maturity (male)

Sex: male:
353 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
353 days.

Female fox squirrels care for their young in the nest for 6 weeks. When the mother leaves her young in the nest she covers them with nesting material. Young fox squirrels move away from their mothers in the fall of their first year. Male fox squirrels disperse farther and may die more as a result.

Parental Investment: altricial

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Sciurus niger

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

Many subspecies of fox squirrels are endangered due to overhunting and destruction of mature forests.

US Federal List: endangered; no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Linzey, A.V., Timm, R., Emmons, L. & Reid, F.

Reviewer/s
McKnight, M. (Global Mammal Assessment Team) & Amori, G. (Small Nonvolant Mammal Red List Authority)

Contributor/s

Justification
This species is listed as Least Concern in view of its wide distribution, presumed large population, occurrence in a number of protected areas, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.
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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N3 - Vulnerable

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

Reasons: Large range in central and eastern U.S. and adjacent south-central Canada; introduced and established in many places in western North America; many occurrences and locally common, but typically rare in the southeastern U.S. where populations have declined and become fragmented due to loss of open mature forest habitat.

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Several subspecies of fox squirrels in the eastern United States are endangered due to overhunting and destruction of forests.

IUCN Red List of Threatened Species: least concern

US Federal List: endangered; no special status

CITES: no special status

State of Michigan List: no special status

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Information on state- and province-level protection status of animals in the
United States and Canada is available at NatureServe, although recent
changes in status may not be included.

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U.S. Federal Legal Status

The Delmarva fox squirrel is Endangered [21].
  • 21. U.S. Department of the Interior, Fish and Wildlife Service. 2013. Endangered Species Program, [Online]

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Status

"The subspecies S. niger shermani, Sherman's fox squirrel, is Near Threatened."
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Population

Population
Abundant. Reported densities vary from 0.04 - 0.12 individuals/ha in the southeastern U.S. to 1.0 - 12 individuals/ha in the mid-west.

Population Trend
Stable
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Threats

Major Threats
No major threats known. Although not considered a major threat at this time, this species is experiencing declining habitats in eastern states, with an increasingly restricted distribution. By contrast, range expansion has occurred in the mid-west. In Mexico, it may be considered fragile, but is not officially threatened (Ceballos and Oliva 2005).
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Comments: The greatest threat is to populations in the southeastern U.S., where distribution and abundance have been reduced by loss of mature forest habitat. The widely spaced trees typical of mature longleaf pine-turkey oak forest upon which populations in the southeastern U.S. depend favor the squirrel's large size, running proficiency, and tendency to escape along the ground. The very open, parklike forest stands resulting from frequent fires produce better crops of pine cones and mast (Goodrum 1938, Smith and Follmer 1972, Weigl et al. 1989). However, the longleaf pine ecosystem, which once comprised some 70 million hectares across the southeastern Coastal Plain, is today represented by only about 2% of its original range (Ware et al. 1993). Survival of the fox squirrel in the Southeast is intimately tied to the fortunes of this declining ecosystem. The squirrel's longleaf pine forest habitat is considered to be a fire climax (Waggoner 1975, Boyer and Peterson 1983, Christensen 1988, Platt et al. 1988). When fire is excluded, hardwoods become more abundant, the canopy begins to close, and the community begins to merge with adjacent deciduous forests and wetlands. These conditions favor the more abundant gray squirrel, which prefers densely stocked stands, dense undergrowth, and which tends to move through the canopy. While human modification of landscape has generally benefited fox squirrels in the western part of the range (Hibbard 1956, Weigl et al. 1989), fox squirrels in the southeastern U.S. have generally suffered. Their large body size requires substantial food supplies and large nesting cavities. These are found in open stands of mature, mast-producing trees. When these forests are logged, the second growth woodland that replaces these habitats, often with a dense understory, provides less of both key resources and also places a large cursorial species like the fox squirrel at higher risk of predation (Taylor 1973, Weigl et al. 1989). In addition, closed-canopy deciduous woodland with a well-developed understory favors the gray squirrel over most fox squirrels, and particularly over fox squirrels in the Southeast (Nixon and McCain 1969; Havera and Nixon 1978, 1980; Weigl et al. 1989). Home ranges of sympatric fox squirrels and gray squirrels may overlap without exclusion (Armitage and Harris 1982), but where the two species are in competition for the same but reduced food resources, lower energetic costs and higher reproductive potential favors the more numerous gray squirrel, particularly in years of poor mast production. Gray squirrels occur at higher densities, are able to exploit more numerous, smaller tree cavities and canopy food sources not available to fox squirrels, and are more likely to survive mast failures. Fox squirrels in the southeastern U.S. are highly adapted to and dependent on limited food supplies, so that anything that diminishes the quantity or quality of that habitat can have devastating effects. Because of their cursorial abilities and large size, which enable them to handle the massive cones of longleaf pine, they have an almost exclusive resource base as long as sufficiently extensive and mature tracts of this habitat exist. Habitat loss to development and agriculture is exacerbated by the conversion of pine-oak forests to large, heavily managed, short-rotation pine plantations, which provide little or none of the required food resources. Remaining longleaf and other pine forests are too small, too young, or too disturbed to provide adequate supplies of food (Weigl et al. 1989). Isolated patches of suitable habitat in the southeastern U.S. might still support fox squirrels that can move easily between them, but secondary succession in old fields and residential development has created migration corridors for gray squirrels, linking previously isolated fox squirrel habitat and enabling invasion by the more numerous gray squirrels (Weigl et al. 1989). Continued fragmentation of longleaf pine habitat also increases distances over which fox squirrels must travel in search of food, particularly in poor mast years. These factors put squirrels at greater risk of mortality from automobile traffic and predation by feral dogs. While leaf nests are built and used by fox squirrels in the southeastern U.S., cavity nests apparently are preferred for rearing young and as protection from severe weather conditions. Because the pine-oak forest typical of much of the squirrels' range is too young to have large numbers of suitable cavities, squirrels must rely on leaf nests, which may put their young at greater risk of predation, or they resort to cavities in adjacent bottomland forests where competition from other species may be high. Another threat to fox squirrel population in the southeastern U.S. may be their status as game animals. Weigl et al. (1989) suggested that, in large areas of good habitat, fox squirrel populations can probably support moderate hunting pressure, since low densities discourage hunters from specifically targeting fox squirrels. However, because of the squirrel's low reproductive rate, as the amount of suitable habitat continues to decline, hunting of smaller and more disjunct populations of squirrels could threaten regional survival of the species. Williams (1994) suggested that fox squirrel populations in longleaf pine sandhills in South Carolina may be adversely affected by hunting pressure. In these resource-poor habitats populations are "just hanging on." However, populations in bottomland hardwood areas may be able to better withstand hunting. Competitive and predation pressures on fox squirrels in the southeastern U.S. will increase as the acreage of preferred mature pine-oak forest is reduced and fox squirrels are forced into bottomland and successional forest, pine plantations, and developed areas. In addition, where large gray squirrel populations increase the prey base, sympatric fox squirrels may suffer higher predation, which an animal with low reproductive rates may not be able to support. Consequently, as the fox squirrel is forced into marginal habitats that favor other sciurids, they may be eliminated. See also files for subspecies.

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Management

Conservation Actions

Conservation Actions
Occurs in many protected areas.
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Restoration Potential: In general, recovery may be possible if large tracts of forest are preserved, degraded habitat is restored, and habitat fragmentation is minimized.

Subspecies SHERMANI: Recovery potential is low due to the squirrel's low rate of reproduction and recruitment. Preferred habitat, the longleaf pine/wiregrass sandhills, has potential for recovery if the ground cover of wiregrass and associated herbs is relatively intact and if a natural fire regime is initiated. Longleaf pine and wiregrass can be replanted, but little is known about the restoration of other herbs.

Preserve Selection and Design Considerations: Adequate land-use restrictions (buffer zones) around protected populations, and protection of the habitat between protected populations (wildlife corridors), are important considerations in selecting and designing preserves (Cox, unpublished manuscript, 1990).

Kantola (1986) cited the Ordway/Swisher Preserve (Putnam County, Florida) as a good example of a minimum refuge of more than 10 sq km necessary to sustain a viable population of about 200 fox squirrels.

The typically low diversity and seasonality of resource availability in fox squirrel habitat in the southeastern U.S. means that large areas are needed to support fox squirrel populations and reduce potential conflicts with gray squirrels, which are better adapted to exploit hardwood forest and wetland areas. Kantola and Humphrey (1990) and Kantola (1992) suggested the preservation/reclamation of large (at least 25 sq km) areas of heterogeneous natural sandhills vegetation, including both uplands and lower slopes. U.S. Forest Service plans to preserve management areas of greater than 10,000 acres (approximately 40 sq km) for red-cockaded woodpeckers should go far toward the maintenance of fox squirrel populations, with certain caveats.

Management Requirements: Effective land protection in the southeastern U.S. depends upon the protection and restoration of mature longleaf pine-turkey oak sandhill habitats (Weigl et al. 1989, Kantola and Humphrey 1990). Active management of existing intact stands of mature longleaf pine is necessary to restore or maintain the open, parklike understory and prevalence of mast-producing trees. Land management should aim to protect large areas of longleaf pine, as well as associated habitats, notably hardwood bottomlands of suitable age to insure the production of mast, in order to promote the mosaic of habitat types most beneficial to the squirrel (Weigl et al. 1989).

Forest management that mimics natural disturbance regimes should benefit the squirrel. Fire regimes that approach historic patterns (e.g., fire return period of 1-5 years) are necessary to control hardwood understory, prepare a suitable seed bed for longleaf pine, and provide the open, parklike stands required by fox squirrels in the Southeast. Fire exclusion results in an altered canopy, reduced mast production, and creation of habitats that tend to place fox squirrels at a competitive disadvantage compared to coexisting gray squirrels. However, the presence of mature oaks should be encouraged to provide mast and suitable nest cavities (Weigl, pers. comm.).

Means and Grow (1985) concluded that the only hope for longleaf pine is to save and properly manage forests on public lands (e.g., Florida's national forests). They suggested a need for significant change in the management of the national forests. Changes would include such strategies as increases in summer burns, road closures, and reforestation with longleaf pine.

Widespread modification of mature pine-oak communities have also led to fragmentation of squirrel populations and reduced quality of remaining habitats. Efforts are needed to ensure that habitat patches are joined by suitable movement corridors. Changes in timber rotations and control of firewood cutting are critical to a sustained supply of suitable nest cavities (Weigl, pers. comm.). In Florida, traditional management for bobwhite has damaged habitat for fox squirrel (Kantola and Humphrey 1990).

Concern for the endangered red-cockaded woodpecker generated increased interest in the preservation and restoration of the longleaf pine forest ecosystem. Because of its large size, and consequent large home range, and its dependence on mature forest stands, the fox squirrel integrates the needs of many other plants and animals dependent on this shrinking resource.

In general, management recommendations for woodpecker habitat, as outlined in the U.S. Forest Service Regional Wildlife Habitat Management Handbook, would apply equally well to the fox squirrel. In particular, institution of a regime of growing season fires on a 2-3-year rotation to control the hardwood midstory, maximize the regeneration and growth of groundcover, and prepare a suitable seedbed for longleaf pine, is important to the maintenance of fox squirrel habitat as well. Reducing physical impediments to burning, including roads and habitat fragmentation, would help reduce the isolation of squirrel subpopulations. Also, the use of uneven-aged timber management based on a rotation age of 70 to 120 years, depending on the pine species, would help provide contiguous areas of foraging habitat for both squirrels and woodpeckers. Williams (1994) pointed out that mechanical site preparation (e.g., roller chopping) should avoid removal of scrub oaks more than 10 inches in diameter.

However, Weigl et al. (1989) pointed a number of instances where woodpecker management and fox squirrel management may conflict. The primary difference between the woodpecker and the fox squirrel lies in the provision of hardwood forest habitats for the squirrel. Removal of all or most of the larger oaks and hickories from among the older pine-oak stands would have a devastating effect on food supply and nest cavity availability for fox squirrels. While hardwood mid-story control would be beneficial, managers should strive to maintain scattered oak trees at least 30 years old or oak groves. A minimum of 10 to 12 large oak trees per acre (25 to 30 trees per hectare) should be left (Weigl, pers. comm.). Fox squirrels prefer nesting in larger hardwood snags and, if such substrates are available, should not compete with woodpeckers for cavity sites (Weigl, pers. comm.). Removal of hardwoods may also increase competition between the woodpecker and other cavity-dependent species.

Preservation of the mature pine-oak forest must also include protection for adjacent lowland habitats. Mature pine forest is not the only habitat type used or required by the squirrel and it need not occur in single large units. A mosaic of habitats, with a substantial mature pine-oak component and access to bottomland forest, appears as beneficial to squirrels as large unbroken tracts of pine forest. Hardwood stringers should be maintained, since fox squirrels heavily utilize lower-lying hardwood areas during dry periods. However, if only stringers are preserved for fox squirrels, with no other hardwood habitats in the upland, fox squirrels may be outcompeted by gray squirrels (Weigl, pers. comm.).

Mixed stands of mast-producing trees are recommended to compensate for variable seed production (Goodrum et al. 1971, Sork 1983). In addition, it should be borne in mind that longleaf pine, upon which fox squirrels depend, have heavy mast crops at intervals of five to seven years, suffer complete crop failures only once or twice every five years, and are only moderately productive in intervening years (Wahlenberg 1946, Schopmeyer 1974, Maki 1952). Land managers can predict mast years from the number of green cones in June, leaving several months to burn in those years best for pine production (Kantola and Humphrey 1990).

Another management consideration is the fox squirrel's status as a game animal across most of its range. Given the possible detrimental effect of hunting on fox squirrels (Wood 1987; Weigl et al. 1989; Noss, pers. comm., 1990), many biologists believe that no hunting of subspecies SHERMANI should be permitted until shown justifiable based on adequate demographic data. Weigl et al. (1989) stated that squirrel populations in the southeastern U.S. probably can support moderate hunting pressure (low bag limit), since low squirrel densities discourage hunters from specifically targeting fox squirrels (Weigl et al. 1989). However, hunting should be confined to the late fall and should be closely monitored. However, as fox squirrel habitat becomes smaller, more fragmented, and more degraded, hunting pressure conceivably could extirpate small relictual populations. Incidental take by sportsmen hunting other species of game might be another deleterious effect of allowing hunting in fox squirrel habitat (Brady 1976).

Because fox squirrels are relatively slow and easy to catch (Noss, pers. comm., 1990), domestic dogs should not be allowed to range freely in occupied fox squirrel habitat.

Management plans need to be developed for many populations of subspecies CINEREUS. Efforts to reintroduce populations of this subspecies into suitable unoccupied habitat should be continued. Bendel and Theres (1994) reported the following results of a translocation in Maryland. Of 20 wild-trapped, translocated squirrels, at least nine died during the first few months after release. All translocated squirrels remained on the release site. The mean distance moved fom the release point was 589 m. Squirrels released in mid-spring moved farther from the release point than did those released in mid-autumn.

See Teaford (1986) for specifications for the construction and placement of wooden nest boxes and rubber tire shelters.

Fox squirrels may be repelled from holes in wooden walls and roof shingles by using paradichlorobenzene or napthalene (moth balls of crystals). Gnawing of plant stems or tree bark may be reduced with the application of tetramethylthiuram disulfide. Methyl nonyl ketone crystals and paradichlorobenzene are used to repel animals from garden and property borders but effectiveness is questionable (see Koprowski 1994).

See also Nixon and Hansen (1987) and files for subspecies.

Management Research Needs: There has been considerable research on fox squirrels over much of the range in the west. The ecology of southeastern populations has been much less well studied, although Weigl et al. (1989) presented a detailed and comprehensive review of the current state of our understanding. The distribution of habitat types on the southeastern Coastal Plain landscape has important consequences for fox squirrels. Additional research is required on the relationships between fox squirrels and longleaf pine habitats, as well as on viable population sizes. Research should address how the size and distribution of habitat patches affects dispersal pattern and, ultimately, gene exchange among local populations.

Biological Research Needs: See MGMT.RSRCH.NEED in element stewardship (ES) files.

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Use of Fire in Population Management

More info for the term: fire management

Prescribed fire can be used to maintain eastern fox squirrel habitat.
Prescribed burning at 2- to 5-year intervals can be beneficial to eastern fox
squirrels by maintaining an open understory and better foraging habitat
[11]. According to Humphrey [24], ground fires are valuable in
maintaining habitats of Big Cypress fox squirrels. In the habitat of
this subspecies, future fire management plans call for an increase in
prescribed burning to 50,000 acres a year. Pinelands are expected to be
burned on a 5- to 7-year rotation [24].
  • 11. Kirkpatrick, Roy L.; Mosby, Henry S. 1981. Effect of prescribed burning on tree squirrels. In: Wood, Gene W., ed. Prescribed fire and wildlife in southern forests: Proceedings of a symposium; 1981 April 6-8; Myrtle Beach, SC. Georgetown, SC: Clemson University, Belle W. Baruch Forest Science Institute: 99-101. [14815]
  • 24. Humphrey, Stephen R.; Jodice, Patrick G. R. 1992. Big Cypress fox squirrel: Sciurus niger avicennia. In: Humphrey, Stephen R., editor. Rare and endangered biota of Florida. Mammals: Volume 1. Naples, FL: Florida Game and Fresh Water Fish Commission: 224-233. [21060]

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Management Considerations

More info for the term: natural

The range of eastern fox squirrels in the the eastern states has been greatly
reduced in the past 100 years [5]. Habitat reduction is one cause. The
Coastal Plain of North Carolina and other southern states is undergoing
rapid deforestation and forest modification due to accelerated
residential and agricultural development, and intensive management
techniques in commercial forests [23]. Another major cause of eastern fox
squirrel population decline is mange mite (Cnemidoptes sp.) along with
severe winter weather [5].

One of the primary reasons for the decline of the endangered Delmarva
fox squirrel is timber harvest. As large trees are removed so are much
of the areas that provide the Delmarva fox squirrel with an open
understory habitat. With loss of habitat, this subspecies is forced to
compete with gray squirrels (Sciurus carolinensis) for food and nesting
resources. Logging practices that include harvesting all the big
hardwoods and replacing them with stands of pure loblolly pine are also
detrimental to Delmarva fox squirrels, since stands of pure species do
not provide good fox squirrel habitat [19].

In addition, the effects of timber harvest prohibit eastern fox squirrel habitat
from developing. At the point where trees become of a salable size,
they are not large enough to provide sufficient food and den sites for
squirrel utilization [19].

Habitat can be improved for eastern fox squirrels by selective cutting to
encourage nut-bearing trees and other food species; planting corn and
soybeans; leaving overmature and large-crowned trees; and opening up the
forest understory by burning or light grazing [5]. Maintenance of
wooded fencerows and breaking up forests into small, 5- to 10-acre (2-4
ha) woodlots of irregular shapes also would promote eastern fox squirrel
populations [5].

In cut-over areas where all den trees have been removed, den boxes can
be used to supplement natural den trees. Den boxes are very useful on
prairies and young woodlots where there is a shortage of natural
cavities [20]. Use of artificial den boxes is an important part of the
recovery plan for the Delmarva eastern fox squirrel [9].
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 9. Gilley, Susan. 1982. The non-game update: the Delmarva fox squirrel; making a comeback?. Virginia Wildlife. 43(12): 24-25. [3463]
  • 19. Taylor, Gary J. 1974. Present status and habitat survey of the Delmarva fox squirrel (Sciurus niger cinereus) with a discussion of reasons for its decline. Proceedings, Southeastern Association Game & Fish Commissioners. 27: 278-289. [21088]
  • 20. Terrill, Harold V.; Crawford, Bill T. 1946. Using den boxes to boost squirrel crop. Missouri Conservationist. 7: 4-5. [16740]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]

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Relevance to Humans and Ecosystems

Benefits

Squirrels are often considered a nuisance species due to their raiding of bird feeders and gardens. They are also responsible for some damage to corn crops. They often use electrical lines as routes of travel, and this can cause power outages.

Negative Impacts: crop pest

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Squirrels are be hunted as a food source and for their fur, although the fur is not very valuable. In addition, fox squirrels are important agents of seed dispersal and can aid in succession by burying forest nuts. May play some role in the dispersal of mycorrhizal fungi.

Positive Impacts: body parts are source of valuable material

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Economic Uses

Comments: Popular game species. Sometimes damages crops of nuts or fruits, but losses generally are not excessive (Koprowski 1994).

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Economic Importance for Humans: Negative

Some people think squirrels are a nuisance because they raid bird feeders and gardens. They sometimes damage corn crops. They often use electrical lines as routes of travel, and this can cause power outages.

Negative Impacts: crop pest

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Source: BioKIDS Critter Catalog

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Economic Importance for Humans: Positive

Fox squirrels are hunted for food and for their fur, even though the fur is not very valuable. In addition, fox squirrels are important tree seed dispersers.

Positive Impacts: body parts are source of valuable material

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Risks

Stewardship Overview: [Note: This document pertains primarily to fox squirrel populations in the southeastern U.S.]

Active management is required to restore degraded pine-oak forests to maintain existing fox squirrel populations and recover declining populations. Land protection through acquisition, easement, and registry programs is the best means of ensuring that large tracts of suitable habitat are preserved. Habitat fragmentation, which may put populations of the large, cursorial fox squirrel at greater risk, should be avoided. Censuses are needed to determine the status of the species in the remaining longleaf pine-turkey oak habitats in the Southeast. Monitoring programs are needed to assess the impacts of hunting and habitat modification on population size and demography.

Management of public lands, including the national forests and military installations, offer the best opportunities for protection of longleaf pine habitats, with such protection efforts often being driven by recovery of the red-cockaded woodpecker (PICOIDES BOREALIS). Management plans for the woodpecker should be adapted to take into account the requirements of the fox squirrel, particularly when the needs of the two species do not conflict. Public education regarding the preservation and restoration of the longleaf pine ecosystem should include information about the habitat requirements of the fox squirrel and its status in the Southeast.

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Wikipedia

Fox squirrel

The fox squirrel (Sciurus niger), also known as the eastern fox squirrel or Bryant's fox squirrel,[1] is the largest species of tree squirrel native to North America. Despite the differences in size and coloration, they are sometimes mistaken for American Red Squirrels or Eastern Gray Squirrels in areas where both species co-exist.[3]

Distribution[edit]

The fox squirrel's natural range extends throughout the eastern United States, north into the southern prairie provinces of Canada, and west to the Dakotas, Colorado, and Texas. They are absent (although sometimes vagrants) from New England, New Jersey, most of New York, as well as Northern and eastern Pennsylvania. They have been introduced to both northern and southern California,[4] Oregon,[5] Idaho,[6] Montana,[6] Washington,[6] and New Mexico.[6] 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 best among trees such as oak, hickory, walnut, and pine that produce winter-storable foods like nuts. Western range extensions in Great Plains regions such as Kansas are associated with riverine corridors of cottonwood. A subspecies native to several eastern US states is the Delmarva fox squirrel (S. n. cinereus).[7]

Habitat[edit]

Eastern 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.[8] The size and spacing of pines and oaks are among the important features of eastern fox squirrel habitat. The actual species of pines and oaks themselves may not always be a major consideration in defining eastern fox squirrel habitat.[7] Eastern fox squirrels are often observed foraging on the ground several hundred meters from the nearest woodlot. Eastern fox squirrels also commonly occupy forest edge habitat.[9]

Eastern 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.[10][11] Leaf nests are built during the summer months in forks of deciduous trees about 30 feet (9 m) above the ground. Eastern fox squirrels use natural cavities and crotches (forked branches of a tree) as tree dens.[10] Den trees in Ohio had an average diameter at breast height (d.b.h.) of 21 inches (53 cm) and were an average of 58.6 yards (52.7 m) from the nearest woodland border. About 88% of den trees in eastern Texas had an average d.b.h. of 12 inches (30 cm) or more.[8] Dens are usually 6 inches (15 cm) wide and 14 to 16 (35–41 cm) inches deep. Den openings are generally circular and about 2.9 to 3.7 inches (7.3–9.4 cm). Eastern 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 (Colaptes auratus) or red-headed woodpeckers (Melanerpes erythrocephalus). Crow nests have also been used by eastern fox squirrels.[11]

Eastern fox squirrels use leaf nests or tree cavities for shelter and litter rearing.[8] 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 15 inches (38 cm) or more generally provide adequate cover and reproductive habitat. Optimum tree canopy closure for eastern fox squirrels is from 20% to 60%. Optimum conditions understory closure occur when the shrub-crown closure is 30% or less.[8]

Food habits[edit]

Manipulation of food items by paws and head.
Eating a Santa Rosa plum in Fullerton, CA, US

Food habits of eastern fox squirrels depend largely on geographic location.[12] In general, eastern fox squirrel foods include mast, tree buds, insects, tubers, bulbs, roots, bird eggs, seeds of pines and spring-fruiting trees, and fungi. Agricultural crops such as corn, soybeans, oats, wheat, and fruit are also eaten.[7][8][11][12] Mast eaten by eastern fox squirrels commonly includes turkey oak (Quercus laevis), southern red oak (Quercus falcata), blackjack oak (Quercus marilandica), bluejack oak (Quercus incana), post oak (Quercus stellata), and live oak (Quercus virginiana).[7]

In Illinois, eastern fox squirrels rely heavily on hickories from late August through September. Pecans, black walnuts (Juglans nigra), osage orange (Maclura pomifera) 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.[12]

During the winter in Kansas, osage orange is a staple item supplemented with seeds of the Kentucky coffee tree (Gymnocladus dioicus) and honey locust (Gleditsia triacanthos), corn, wheat, eastern cottonwood (Populus deltoides var. deltoides) bark, ash seeds, and eastern red cedar (Juniperus virginiana) berries. In the spring, eastern fox squirrels feed primarily on buds of elm, maple, and oaks but also on newly sprouting leaves and insect larvae.[12]

Eastern 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. Eastern fox squirrels also eat buckeyes, seeds and buds of maple and elm, hazelnuts (Corylus spp.), blackberries (Rubus 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) acorns, black oak (Quercus velutina) acorns, red oak (Quercus rubra) acorns, walnuts, and corn.[12]

In eastern Texas, eastern fox squirrels prefer the acorns of bluejack oak, 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, eastern fox squirrels feed on English walnuts (J. regia), oranges, avocados, strawberries, and tomatoes. In midwinter, they feed on eucalyptus seeds.[12]

In Michigan, eastern 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), silver maple (Acer saccharinum), and elms. Summer foods include a variety of berries, plum and cherry pits, fruits of basswood (Tilia americana), fruits of box elder (Acer negundo), black oak acorns, hickory nuts, seeds of sugar (Acer saccharum) and black maple (Acer nigrum), grains, insects, and unripe corn. Fall foods consist mainly of acorns, hickory nuts, beechnuts, walnuts, butternuts (Juglans cinerea), and hazelnuts. Caches of acorns and hickory nuts are heavily used in winter.[12]

Description[edit]

The squirrel's total body length measures 45 to 70 cm (17.7 to 27.6 in), tail length is 20 to 33 cm (7.9 to 13.0 in), and they range in weight from 500 to 1,000 grams (1.1 to 2.2 lb).[7] There is no sexual dimorphism in size or appearance. Individuals tend to be smaller in the west. There are three distinct geographical phases in coloration: In most areas the animals 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 can be found isolated communities with uniform black coats. To help with climbing, they have sharp claws, developed extensors of digits and flexors of forearms, and abdominal musculature.[13] Fox squirrels have excellent vision and well-developed senses of hearing and smell. They use scent marking to communicate with other fox squirrels.[13] "Fox squirrels also have several sets of vibrissae, thick 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."[13]

Fox squirrel foraging in the grass in Indianapolis, IN.

Behavior[edit]

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.

They are not particularly gregarious or playful, in fact they have been described as solitary and asocial creatures, coming together only in breeding season.[14] They have a large vocabulary, consisting most notably of an assortment of clucking and chucking sounds, not unlike some "game" birds, and they warn the listening world of approaching threats with distress screams. In the spring and fall, 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.[13]

They are impressive jumpers, easily spanning fifteen feet in horizontal leaps and free-falling twenty feet or more to a soft landing on a limb or trunk.

Reproduction[edit]

Baby

Female eastern 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.[12] Females become sexually mature at 10 to 11 months of age and usually produce their first litter when they are a year old.[12]

Gestation occurs over a period of 44 to 45 days. 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.[12]

Tree squirrels develop slowly compared to other rodents. At birth, the young are blind, without fur and helpless. Eyes open at 4 to 5 weeks of age and ears open at 6 weeks. Eastern fox squirrels are weaned between 8 and 10 weeks but may not be self-supporting until 12 weeks.[11][12] Juveniles usually disperse in September or October, but may den either together or with their mother during their first winter.[10]

Mortality[edit]

In captivity, eastern fox squirrels have been known to live 18 years, but in the wild most fox squirrels die before they become adults.[13] 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 (the Delmarva fox squirrel for example) are endangered.[13] Another major cause of fox squirrel population decline is mange mite (Cnemidoptes sp.) along with severe winter weather.[12]

Relatively few natural predators can regularly capture adult eastern fox squirrels. Of these predators, most only take eastern fox squirrels opportunistically.[7] Eastern fox squirrel predators include: bobcats (Felis rufus), foxes (Vulpes spp. and Urocyon spp.), red-tailed hawks (Buteo jamaicensis), red-shouldered hawks (Buteo lineatus), great horned owls (Bubo virginianus), barred owls (Strix varia), and dogs (Canis lupus familiaris).[7][10][12] Nestlings and young eastern fox squirrels are particularly vulnerable to climbing predators such as raccoons (Procyon lotor), opossums (Didelphis virginiana), rat snakes (Elaphe obsoleta), and pine snakes (Pituophis melanoleucus). In those states where eastern fox squirrels are not protected, they are considered a game animal.[7] Eastern fox squirrels were an important source of meat for European settlers in the 17th and 18th centuries and are still hunted for food over most of their range.[citation needed] They are hunted more for trophy than for food.[7] Overharvest by hunting has been reported from small woodlots and public shooting areas in Ohio, Michigan, and Indiana.[12]

See also[edit]

References[edit]

 This article incorporates public domain material from the United States Department of Agriculture document "Sciurus niger".

  1. ^ a b Linzey, A. V., Timm, R., Emmons, L. & Reid, F. (2008). Sciurus niger. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 6 January 2009.
  2. ^ Thorington, R.W., Jr.; Hoffmann, R.S. (2005). "Sciurus (Sciurus) niger". In Wilson, D.E.; Reeder, D.M. Mammal Species of the World: a taxonomic and geographic reference (3rd ed.). The Johns Hopkins University Press. pp. 754–818. ISBN 0-8018-8221-4. OCLC 26158608. 
  3. ^ Graham, Donna. "Fox Squirrel (Sciurus niger)". Northern State University. South Dakota Department of Game, Fish and Parks. Retrieved 7 December 2013. 
  4. ^ "Southern California Fox Squirrel Page". www.calstatela.edu. Retrieved 2008-04-25. 
  5. ^ "Mammal Species of Oregon - Squirrels". http://www.dfw.state.or.us/. Retrieved 2014-03-29. 
  6. ^ a b c d "TREE SQUIRRELS AS INVASIVE SPECIES: CONSERVATION AND MANAGEMENT IMPLICATIONS". www.ag.arizona.edu. Retrieved 20014-10-8.  Check date values in: |accessdate= (help)
  7. ^ a b c d e f g h i Van Gelden, Richard George. 1982. Mammals of the National Parks. Baltimore, MD: Johns Hopkins University Press
  8. ^ a b c d e 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
  9. ^ Dueser, Raymond D.; Dooley, James L., Jr.; Taylor, Gary J. 1988. Habitat structure, forest composition and landscape dimensions as components of habitat suitability for the Delmarva fox squirrel. In: Management of amphibians, reptiles, and small mammals in North America: Proceedings of the symposium; 1988 July 19–21; Flagstaff, AZ. Gen. Tech. Rep. RM-166. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 414–421
  10. ^ a b c d Banfield, A. W. F. 1974. The mammals of Canada. Toronto, ON: University of Toronto Press
  11. ^ a b c d MacClintock, Dorcas. 1970. Squirrels of North America. New York: Litton Educational Publishing, Inc.
  12. ^ a b c d e f g h i j k l m n Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Pres
  13. ^ a b c d e f "Sciurus niger page". University of Michigan Museum of Zoology. Retrieved 2009-04-23. 
  14. ^ Carraway, Mike. "Fox Squirrel, North Carolina Wildlife Profiles". The North Carolina Wildlife Resources Commission. n.p. Retrieved 7 December 2013. 
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Names and Taxonomy

Taxonomy

Comments: Western and eastern populations of fox squirrels are markedly different in coloration, habitat preference, and response to human modification of their habitats, which suggest that the two groups evolved in isolation from each other during some portion of the Pleistocene (Weigl and Steele 1986, Moncrief 1987). A third fox squirrel subgroup is described as an artificial one, including two small, variably colored, isolated forms restricted to trophically poor, wetter areas in southern Florida (S. n. avicinnia) and the Mississippi flood plain (S. n. subauratus).

Individuals inhabiting the Mississippi River floodplain and delta region are smaller than individuals from adjacent areas; allozyme analyses revealed that there are differences among eastern and western populations as defined by their geographic location relative to the present channel of the lower Mississippi River (Moncrief 1993).

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Common Names

eastern fox squirrel
stump-eared squirrel
cat squirrel

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The currently recognized scientific name for the eastern fox squirrel is Sciurus
niger L. Ten subspecies are recognized: four eastern, four mid-western,
and two isolated subspecies [5,23].

Eastern fox squirrels are very large (2.4 to 3.2 pounds [900-1200 g]);
gray, agouti, or black; and often have black markings on the head and
white nose, ears, and paws [23]. Eastern fox squirrel subspecies are
listed below:

S. niger ssp. cinerea (Delmarva fox squirrel)
S. niger ssp. niger
S. niger ssp. shermani (Sherman's fox squirrel)
S. niger ssp. bachmani

Mid-western fox squirrels are smaller (1.6 to 2.4 pounds [600-900 g]) and
reddish. Subspecies are as follows [23]:

S. niger ssp. rufiventer
S. niger ssp. vulpinus
S. niger ssp. ludovicianus
S. niger ssp. limitis

A third group is composed of two small, variably colored, and isolated
subspecies: S. n. ssp. avicennia Howell (Big Cypress fox squirrel) and
S. n. ssp. ubauratus [23,24].

While eastern and mid-western subspecies are now widely separated in the
Atlantic States, considerable gene flow is possible in the Gulf Region
[23].

Where appropriate, the Delmarva fox squirrel will be highlighted
in this report.
  • 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]
  • 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032]
  • 24. Humphrey, Stephen R.; Jodice, Patrick G. R. 1992. Big Cypress fox squirrel: Sciurus niger avicennia. In: Humphrey, Stephen R., editor. Rare and endangered biota of Florida. Mammals: Volume 1. Naples, FL: Florida Game and Fresh Water Fish Commission: 224-233. [21060]

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