Index of Species Information
WILDLIFE SPECIES: Sciurus niger
Introductory
WILDLIFE SPECIES: Sciurus niger
AUTHORSHIP AND CITATION :
Tesky, Julie L. 1993. Sciurus niger. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
www.fs.usda.gov/database/feis/animals/mammal/scni/all.html [].
ABBREVIATION :
SCNI
COMMON NAMES :
eastern fox squirrel
stump-eared squirrel
cat squirrel
TAXONOMY :
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.
ORDER :
Rodentia
CLASS :
Mammal
FEDERAL LEGAL STATUS :
The Delmarva fox squirrel is Endangered [21].
OTHER STATUS :
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.
WILDLIFE DISTRIBUTION AND OCCURRENCE
WILDLIFE SPECIES: Sciurus niger
GENERAL DISTRIBUTION :
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].
ECOSYSTEMS :
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
STATES :
| AL |
AR |
CA |
CO |
CT |
DE |
FL |
GA |
ID |
IL |
| IN |
IA |
KS |
KY |
LA |
MD |
MI |
MN |
MS |
MO |
| MT |
NE |
NJ |
NM |
NC |
ND |
OH |
OK |
OR |
PA |
| SC |
SD |
TN |
TX |
VA |
WA |
WI |
|
ON |
MEXICO |
BLM PHYSIOGRAPHIC REGIONS :
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
KUCHLER PLANT ASSOCIATIONS :
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
SAF COVER TYPES :
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 - gray pine
252 Paper birch
255 California coast live oak
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
PLANT COMMUNITIES :
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].
BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Sciurus niger
TIMING OF MAJOR LIFE HISTORY EVENTS :
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].
PREFERRED HABITAT :
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].
COVER REQUIREMENTS :
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].
FOOD HABITS :
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].
PREDATORS :
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].
MANAGEMENT CONSIDERATIONS :
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].
FIRE EFFECTS AND USE
WILDLIFE SPECIES: Sciurus niger
DIRECT FIRE EFFECTS ON ANIMALS :
Eastern fox squirrels would probably not be able to escape fast-moving fires
[15]. However, they could probably easily escape low-severity ground
fires. Kirkpatrick and Mosby [11] found no evidence that prescribed
burning caused significant direct mortality among eastern fox squirrels.
Wildfires could destroy leaf nests, nest trees, and eastern fox squirrel
nestlings. However, cavities used for denning and leaf nests are
usually above the impact zone of prescribed fires [11].
HABITAT RELATED FIRE EFFECTS :
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].
FIRE USE :
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].
FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find Fire Regimes".
REFERENCES
WILDLIFE SPECIES: Sciurus niger
REFERENCES :
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[434]
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North America. Baltimore, MD: The Johns Hopkins University Press. 1147
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structure, forest composition and landscape dimensions as components of
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amphibians, reptiles, and small mammals in North America: Proceedings of
the symposium; 1988 July 19-21; Flagstaff, AZ. Gen. Tech. Rep. RM-166.
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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
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squirrel in the Yellowstone River drainage, Montana. Prairie Naturalist.
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habitats in relation to winter food supply and vegetation density.
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[Date of conference unknown]; [Location of conference unknown]. Gen.
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fox squirrel (Sciurus niger cinereus) with a discussion of reasons for
its decline. Proceedings, Southeastern Association Game & Fish
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20. Terrill, Harold V.; Crawford, Bill T. 1946. Using den boxes to boost
squirrel crop. Missouri Conservationist. 7: 4-5. [16740]
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22. Van Gelden, Richard George. 1982. Mammals of the National Parks.
Baltimore, MD: Johns Hopkins University Press. 310 p. [20893]
23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C.
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Implications for survival in the southeast. Bull. No. 24. Tallahassee,
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squirrel: Sciurus niger avicennia. In: Humphrey, Stephen R., editor.
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endangered fauna and flora in Florida. Tallahassee, FL: Florida Game and
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FEIS Home Page
https://www.fs.usda.gov/database/feis/animals/mammal/scni/all.html
