SquirrelsTop
The gray squirrel is the largest and most common squirrels. The back and sides of
its coat are silver-gray in color and the underparts are white. Various color phases occur
in this species, including several shades of black and red. Its broad, bushy tail is about
the length of its head and body combined. Top
Range:
Gray squirrels occur from southern Quebec, New Brunswick and Ontario to Florida,
west into eastern Texas, and north into southern Manitoba. They have been introduced into
Washington, British Columbia, and Vancouver Island. Top
Reproduction:
Gray squirrels mate in late winter and spring. After a 44-day gestation period,
females give birth to a litter of two to seven young. They are blind and helpless at birth
but are weaned and somewhat independent at eight to 10 weeks of age. The second litter is
usually born in July. The nest is often in a tree cavity or constructed of leaves
suspended in the treetops. These leaf nests are also used for temporary protection against
inclement weather or predators. Top
Interesting Facts:
These tree-dwelling rodents are agile climbers and jumpers. They have keen senses
of sight, smell, and hearing and are alert, nervous and wary, especially on the ground.
When danger is near, they quickly retreat to the safety of the trees. Gray squirrels are
somewhat sociable and can tolerate other squirrels nearby. The gray squirrel is active
year-round but needs tree cavities for shelter during harsh weather. In the fall, gray
squirrels gather and bury, at random, a winter food supply. This food supply is usually
recovered as needed, by sniffing the ground until a buried nut is found. Top
Habits and Ecology
Eastern grey squirrels are active year round during the daytime. Even during the
most severe winter weather they will leave their nests for short periods of time to forage
for food. Activity is bimodal from late spring to autumn with peaks 2 hours after sunrise
and again 2 - 5 hours before sunset. Grey squirrels are non-territorial. They have large
overlapping home ranges which average 5 hectares in size, but can vary from 0.5 hectares
to greater than 20 hectares. Males have slightly larger ranges than females, due to an
increase in their range during the breeding season. Home range sizes also increase during
spring and summer for both sexes and are negatively correlated with food supply and
squirrel population density.
Eastern grey squirrels are most commonly found in mature continuous woodlands greater than
40 hectares in size. Densities are highest in habitats composed of tree species that
produce foods suitable for storing over winter such as oak, hickory and walnut. Due to a
variability in seed production in different years, a diversity of nut trees is important
to support high densities. Top
Grey squirrels are generalist feeders. Eighteen plant species account for 87% of their
diet, but they may feed on as many as 97 plant and 14 animal items. Squirrels feed heavily
on nuts, flowers, and buds of 24 oak species, and 10 species of walnut, hickory and pecan.
Other food items include the fruits, seeds, buds or flowers of maples, mulberry,
hackberry, elms, buckeyes, horse chestnuts, wild cherries, dogwoods, hawthorne, hazelnut
and ginkgo. Pine tree seeds and pollen cones are readily eaten including cedar, hemlock,
pines, and spruce. Fungi are also consumed when readily available in summer, as are
cultivated crops in winter. Animal food items include bones, bird eggs, nestlings, and
frogs. Top
Nests
Eastern gray squirrels typically use 3 different types of nests:
winter dreys, summer dreys, and dens. Dreys are round conspicuous twig and leaf nests
built in trees between 25 and 45 cm in diameter. They are waterproof, and made of an outer
layer of interwoven twigs with a softer inner lining consisting of moss, bark, leaves,
fur, feathers, lichen or other similar material. Summer dreys are less elaborate than
winter dreys and may be no more than twig and leaf saucer shaped platforms on exposed
branches. Dreys are generally built in the upper 1/3 of the canopy and seldom in isolated
trees, which may serve to protect nests from predators.
Tree dens are another type of nest used by eastern gray squirrels. These are holes or
cavities in the main trunks of trees which are also lined with soft material. Formation of
den cavities requires 8 - 30 years, and are more common in deciduous trees than in
coniferous trees. Squirrels often use dens in winter months and dreys in summer months. Top
The southern flying squirrel is found throughout the deciduous forests of eastern
North America from southern Ontario to the Gulf Coast, with isolated populations in Mexico
and as far south as Honduras. Top
Description
The southern flying squirrel is easily distinguished by its gliding membrane, or
patagium, a fold of skin that extends from the wrist of the front leg to the ankle of the
hind leg. When the front and hind legs are extended, the membrane forms a wing-like
gliding surface. The furred, broad and horizontally flattened tail serves as a rudder and
stabilizer during glides. The eyes are noticeably large, an adaptation for its nocturnal
habits. The ears are more prominent than in other tree squirrels. Whiskers are also
prominent. Southern flying squirrels are quite small. Adults usually are nine to 10 inches
long including the tail, and they weigh between two and four ounces. Their fur is soft,
silky and moderately long. The upper body is grayish to brownish in color, and the
underparts are creamy white. The eyes are surrounded by a black ring, and a black border
extends along the edge of the gliding membrane. Top
Flying squirrels produce several vocalizations including a high pitched "tseet"
and other chirping sounds. Some vocalizations are above the frequency range of the human
ear. Some researchers have speculated that flying squirrels use high-pitched sounds for
navigation, similar to the echolocation system of bats. Although flying squirrels have an
excellent sense of hearing, they do not have the highly specialized hearing system of
bats, and echo location is unlikely. Top
Habits
Undoubtedly the most unusual habits of the southern flying squirrel are its
gliding ability and its nocturnal behavior. unlike fox squirrels or gray squirrels that
are active by day, the southern flying squirrel is probably the most nocturnal of all
mammals. Other gliding mammals from various parts of the world also tend to be nocturnal,
and a possible explanation for this association is that gliding in daylight might attract
the attention of hawks or other daytime predators. The gliding of a flying squirrel is
spectacular. Glides begin after the squirrel climbs to a lofty treetop perch and assesses
the landing site by moving its head up and down and from side to side, apparently
triangulating to judge distance. It then launches itself with all four legs extended at
right angles from the body, stretching the flying membrane.
With tremendous agility, flying squirrels can steer around branches or other obstacles.
Most steering is done with the tail, but squirrels also vary the tension on the membrane
to steer and to control speed. They usually land on the vertical trunk of another tree,
invariably upright with the hind feet touching first. Upon landing, they scurry to the
opposite side of the tree to elude any pursuing predator. Glides occasionally extend for
more than 50 yards, but are usually much shorter. Flying squirrels appear to have a
maximum gliding ratio of about three horizontal feet for every vertical foot, a glide
ratio that would allow them to travel the length of a football field from a perch 100 feet
high. Top
Southern flying squirrels do not hibernate, although they may remain in their
nests for several days during severe winter weather. In winter they form groups in a
common nest to conserve warmth. The number of animals in the winter congregations varies
by latitude, with larger con- gregations found in northern climates. Top
The population density of flying squirrels depends on the quality of the habitat. In
favorable habitat, densities can approach five squirrels per acre. Estimates of home range
size, the area used for normal day-to-day activities, range from about one acre to five
acres. Females defend their home range, at least during parts of the year, and there is
little or no over lap with the home range of other females. Males do not defend territory,
and their home ranges often overlap with those of other males. Top
Reproduction
Southern flying squirrels show two periods of breeding activity. The first is in
February and March, and the other is from late May through July. Females can produce two
litters per year but only under favorable conditions. Litters, usually of three or four,
but up to seven young, are born following a gestation period of 40 days. Top
Newborn young are hairless with eyes and ears closed. They are tiny, weighing less than a
quarter-ounce each. The gliding membrane is visible as a transparent fold of skin. The
ears open at about three weeks of age, and a week later the eyes open. The young are
weaned at six to eight weeks and are capable of gliding soon thereafter. Young typically
remain with the female until the birth of the next litter. Top
Adults are sometimes seen together as pairs, but males typically leave females before the
young are born and do not assist in caring for the young. The females are devoted parents.
They seldom leave the new- born young, defend them rigorously and will move the young to a
new nest if disturbed. An accumulation of parasites in the nest may cause the female to
move the young even if no other disturbances are present. Top
Flying squirrels reach sexual maturity at about one year. They do not form tight
pair-bonds. Females frequently have different mates in subsequent breeding seasons. Top
Food
Southern flying squirrels are primarily vegetarian, but will occasionally eat
animal foods. Nuts, primarily acorns and hickory nuts, are preferred foods and make up the
bulk of the diet. Flying squirrels will also consume various seeds, fruits, berries,
mushrooms, buds, flower blossoms and tree bark. Animal items that occasionally may be
eaten include insects, bird eggs and nestlings, small nestling mammals, carrion, and adult
shrews and mice. Top
Nuts are gathered and stored as winter approaches. The shortening of day length rather
than temperature triggers the urge to store food. Nuts are buried individually or are
cached in nest cavities or other cracks and crevices in trees. Several hundred nuts can be
stored in a night. In good nut-production years, the stored nuts carry the squirrels
through the winter and even into spring and summer. Nuts are eaten in a characteristic
pattern. Flying squirrels usually cut a fairly smooth circular or oval opening on the side
or end of a nut. On larger, heavy-shelled nuts they will make a second opening or remove
an entire end in a single cut. Other tree squirrels usually crush nuts without leaving the
shells intact. Top
The feeding pattern of flying squirrels more closely resembles that of deer mice or
white-footed mice, which also inhabit cavities and nest boxes in southeastern Nebraska,
but these species usually do not eat large, heavy-shelled nuts, and their tooth marks are
finer. Flying squirrels will accept a "helping hand" by visiting bird feeders
where they consume seeds, suet and peanut butter. Top
Habitat
ln broad terms, southern flying squirrels require deciduous forests
as habitat. Specifically, they require mast-producing trees such as oaks, hickories and
walnuts for food, cavities in dead or live trees for shelter or and some form of water. Top
Cavities used by flying squirrels are often constsructed by woodpeckers, although any
natural or artificially constructed cavity with an entrance hole larger than one inch in
diameter might be used. Cavities are typically lined with strips of inner bark and leaves,
but lichens, moss, feathers and other materials have been incorporated into nests.
Cavities are used throughout the year. Flying squirrels inhabit a primary nest cavity that
is used more or less continuously and one or more secondary nest cavities used as feeding
stations or as a refuge if the primary nest is disturbed. Outside leaf nests are seldom
used in Northern climates, but are fairly common in warmer areas. Top
The water requirements of flying squirrels are not well understood. They obviously obtain
some water from their food. Free-standing water is consumed when available, but their
range is not limited to areas with available surface water. Where surface water is not
available, squirrels appear to be physiologically adapted and get sufficient water from
food, dew and rains. They probably make use of water that temporarily collects in tree
cavities. Top
Mangrove Fox Squirrel or Big Cypress Fox Squirrel
The Big Cypress fox squirrel is distinctly smaller than Sherman's fox squirrel (Sciurus niger shermani). The head plus body average 28 centimeters long versus 32 centimeters for the Sherman's fox squirrel. Like other subspecies of the fox squirrel it has a long, bushy, fox-like tail and it is highly variable in color, ranging from buff to black. The most frequent color phase of this subspecies is buff, with a buff underside and buff basal bands on the tail hairs, white toes, lips, nose, and eartips, a black crown, and an agouti back. Second in frequency is the black phase, all the coat is black except for white lips, nose, and eartips, white or blackish toes, and agouti feet. The least frequent color phase is tan, with a tan underside and tan basal bands of the tail hairs, white lips, nose, and eartips, white to tan limbs, and agouti cheeks, nape, back and sides. Top
This subspecies is endemic to southwestern Florida, but the species is widespread in eastern and central North America. It occurs in the Immokalee Rise, Big Cypress Swamp, and Devil's Garden area in Collier County. Some areas of this range have become vacated, while many other suitable areas are being altered or becoming isolated through development. The subspecies uses most types of forest occurring in its range. Only the dense interiors of mixed cypress-hardwood strands seem to be avoided, because these are occupied by dense populations of gray squirrels. Big Cypress fox squirrels have been reported in cypress swamp, pine flatwood, tropical hammock, hardwood hammock, mangrove swamp, and suburban habitats including golf courses, and residential areas in native vegetation. Big Cypress fox squirrel densities appear to be quite low, and on this basis the subspecies can be considered inherently rare. Top
Platform nests in pines and hardwoods, and moss and stick nests in cypress, tops of cabbage palms, and large clumps of bromeliads have been observed. Cabbage palms and bromeliads seem especially important, because they allow fox squirrels to range over large areas without the need to construct nests on a daily basis. Fox squirrels often strip bark from cypress trees for incorporation into the nest. They are primarily solitary animals, coinhabiting a nest only during the mating season. Top
Chases and cheek rubbing are a large proportion of social interactions and are observed most frequently during the mating season (May to August). Vocalizing is common during this time, but takes place infrequently outside of mating season. Litters of 2 to 4 young are produced per year. Gestation period is approximately 45 days. The young are weaned at about 2 or 3 months. At one year of age females breed. Fox squirrels have been known to live 10 years or more. Top
Is the most frequent activity. Slash pine seems to be a primary food source for Big Cypress fox squirrels. Individuals have been observed feeding on microstrobili (male cones) in winter, while seeds from magastrobili (female cones) form the bulk of the diet during the summer rainy season. Mega- and microstrobili from cypress are consumed in autumn and early winter, respectively. Cabbage palm fruits, bromeliad buds, and acorns also are important food items. Fox squirrels on golf courses have been observed eating all the above, plus, on a regular basis, queen palm fruits, fig fruits, and fungi. They are known to cache fruits and acorns when they are ground foraging. During wet seasons and when there is a lack of understory and closed canopy, fox squirrels may be observed traveling long distances in order to obtain sufficient food resources. Top
Inactive time varies seasonally, peaking in the humid summer months. Diurnal inactivity may last from a few minutes between foraging events to several hours during extreme weather. During warmer weather fox squirrels often lie draped over a branch or palm frond, with legs dangling on opposite sides. Animals resting this way often remain motionless even when disturbances are present. During cooler weather, fox squirrels sit-up on branches, covering their backs with their tails. Top
Early reports considered habitat destruction to endanger the Big Cypress fox squirrel. While public acquisition of large parcels of land in the subspecies' range has reduced the majority of this threat, large-scale residential and commercial development of pine flatwoods west of Big Cypress National Preserve, conversion of forested wetlands to citrus north of Big Cypress National Preserve, and expansion of Interstate 75 (along with increased local traffic on State Road 29) still pose serious threats to habitat quality and quantity. This loss of habitat will make the distribution smaller and will further isolate remaining populations of squirrels. For instance, some of the populations at golf courses in Naples now are completely isolated from source and dispersal areas by urban growth that has claimed native habitats formerly connecting the golf courses. Top
Since 1990, the Big Cypress fox squirrel has been listed as threatened by the Florida Game and Fresh Water Fish Commission and it currently under review for possible listing by the U.S. Fish and Wildlife Service. Top