BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Sciurus niger | Fox Squirrel 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Breeding season - Female fox squirrels come into estrus in mid-December
or early January and again in June.  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 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 fox squirrels are 4 to 5 weeks old, and ears
open at 6 weeks.  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 - Fox squirrels generally live up to 6 years in the wild but
have survived 13 years in captivity [5,16].


PREFERRED HABITAT : 
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 fox squirrel habitat.  The actual
species of pines and oaks themselves may not always be a major
consideration in defining fox squirrel habitat [23].  Fox squirrels are
often observed foraging on the ground several hundered meters from the
nearest woodlot.  Fox squirrels also commonly occupy forest edge habitat
[6].

In general, the woodland habitats occupied by the Delmarva fox squirrel
are simular to those occupied by other subspecies of 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 - 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.  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).  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 fox squirrels [16].


COVER REQUIREMENTS : 
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 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 fox squirrels depend largely on geographic location [5].
In general, 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 sqirrels
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, 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, fox squirrels feed
primarily on buds of elm, maple, and oaks but also on newly sprouting
leaves and insect larvae [5].

Fox squirrels in Ohio prefer hickory nuts, acorns, corn, and black
walnuts.  The squirrels are absent where two or more of these mast trees
are missing.  Fox squirrels also eat buckeyes, seeds and buds of maple
and elm, hazelnuts (Corylus spp.), blackberries (Rubus spp.), and tree
bark.  In March, they feed mainly on buds and seeds of elm, maple, and
willow.  In Ohio, 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, 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, fox squirrels feed on English walnuts (J.
regia), oranges, avocados, strawberries, and tomatoes.  In midwinter,
they feed on eucalyptus seeds [5].

In Michigan, fox squirrels feed on a variety of foods throughout the
year.  Spring foods are mainly tree buds and flowers, insects, bird
eggs, and seeds of red maple (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 fox
squirrels.  Of these predators, most only take fox squirrels
opportunistically [23].  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 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 fox squirrels are
not protected, they are considered a game animal [5,23].  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 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 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 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 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 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 artifical den boxes is an important part of the
recovery plan for the Delmarva fox squirrel [9].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Sciurus niger | Fox Squirrel