Rodents are the largest order of mammals in the
Appalachian region (as well as the world), both in species and actual numbers.
In fact, 40 % of the world’s mammalian species are rodents.
The diversification of species has been a relatively recent and rapid
evolutionary event, with few extinctions, causing much consternation among
taxonomic botanists.
Rodents
are the "gnawing" mammals. Rodents are known for their pair of large
upper and lower chisel-like incisors. Each incisor is a segment of
a true circle, continuously being pushed out of the end of the jaw. Some species have incisor growth rates of one
inch per month. Unlike lagomorphs that have enamel covering the entire
incisors, rodents only have hardened enamel on the anterior (front) side of
the incisors. This keeps a sharp
edge on the teeth, since the relatively soft posterior (back) side of the
teeth wears more quickly than the front. Also
unlike lagomorphs, rodents have only one pair of upper incisors, instead of two
permanent pair. These incisors grow throughout the life of the
rodent, kept in proper length by grinding of the teeth, not necessarily by
gnawing plants. Rodents lack canines, with the gap between the incisors and molars
known as the diastema. This large
gap allows rodents to curl their lips backward into it while gnawing and chewing. This behavior also permits the rodent to exclude unwanted
soil and debris from its diet. This
also enables muskrats and beaver to eat underwater without inhaling water.
The grinding molars, or "cheek" teeth, are a combination of
vertical layers of dentine and harder enamel, which produce peculiar ridged
patterns on the crown of the teeth, useful in classification by zoologists.
Rodents
have diversified to adapt to a variety of lifestyles including terrestrial
(mice and voles), arboreal (squirrels), fossorial (woodchucks), semiaquatic
(beavers and muskrats), and volant (flying squirrels). They range in size from
a third of an ounce of the harvest mouse, to the eighty pound beaver. All are
herbivores.
With
the cooling and drying out of much of North America during the Tertiary and the
Eocene (40-55 million years ago), forests transformed into grasslands, with the
concurrent evolution and diversification of mammals. Grasses became the
most important of all the flowering plants and became the nutrient source
base of wildlife herbivores, domestic grazing livestock, and, in fact,
mankind. As the plants provided an abundant energy source, herbivores
expanded in number and evolved into the ecological niches. The ungulates
evolved in the Eocene, the grass-eating marsupials arose 25-38 million years
ago, and the voles of the microtus genus were the last to emerge, about 10
million years ago. They have rapidly evolved and diversified for the past
6 million years filling all grassland niches.
In
order for rodents to fill out the grassland niches, two adaptations were
necessary. First, as a result of the abrasive silicas in the cells of grasses,
teeth, easily worn down by the silicas, became ever-growing throughout the life
of the rodent. The second adaptation was the ability of the herbivores to
digest the complex carbohydrates contained in the fibrous portion of grasses
through fermentation in the animal's gut by microorganisms.
The
success of the rodents became a problem in itself as carnivores evolved to
take advantage of this abundant new food source. In response, special
reproductive adaptations evolved to enable massive birth rates within the rodent order.
This includes "postpartum estrus" in mice, with females being mated
within hours of birthing.
Rodents
have four toes (sometimes five) in front and five toes in the rear.
Rodents
are known from fossils in North America dating back to late in the Paleocene
Epoch (60 million years ago).
Worldwide,
the rodent order is represented by 29 family, 468 genera and 2,052 species
(Nowak's Walker's Mammals of the World).
In North American, there are 9 families, 43 genera, and 217 species
(Jones' Checklist of North American Mammals). In the eastern United States, there are
about 38 species and five introduced
species.
Rodents
include twenty nine species in the Appalachian region within five families.
These include the squirrel - which includes the groundhog - (Sciuridae),
beaver (Castoridae), porcupine (Erethizontidae),
mice, rat and vole (Muridae), and
jumping mice (Zapodidae) families.
Family
Sciuridae - Squirrels and Woodchucks
This
family can be divided into three groups; tree squirrels, flying squirrels, and
ground-dwelling squirrels (woodchucks and chipmunks). Tree squirrels are
diurnal, leading solitary territorial lives, living on nuts and fruit.
The woodchuck and chipmunk are also diurnal.
Flying squirrels are nocturnal and tend to be more omnivorous.
The family name means "shade tail", alluding to the large
bushy tail of the arboreal tree sciurids. Most of these family members stand
on their haunches to view their surroundings. Most members of the sciurids
have high birth rates to compensate for their high mortality, especially to
the weasel family (R-selected strategy populations, like the lagomorphs). Squirrels come
in different sizes, habits, and habitats to maximize utilization of available
resources and to minimize competition among species.
They have the largest brains relative to their body size of all small
mammals and are the most intelligent of the rodents, as is reflected in their
complex vocalizations and social systems.
Some are arboreal (red, gray, and fox squirrels), some are
semifossorial - burrowers (prairie dogs, ground squirrels, woodchucks), and
some do both (chipmunks). Some
hibernate (woodchucks), some enter deep torpor and feed occasionally on cached
food supplies (chipmunks), and many are active year-round.
Squirrels
manufacture enzymes that enable them to eat the toxic amanita mushrooms.
However, like the pit viper that produces its venom and the skunk that
produces its musk, the squirrels produce these enzymes at a physiological
cost, thus “balancing” the benefit.
The
front foot (hand) has four toes and the rear foot has five toes.
Worldwide,
the 51 genera and 272 species of the squirrel family includes marmots,
woodchucks, prairie dogs, ground squirrels, chipmunks and tree squirrels
(Nowak's Walker's Mammals of the World).
They
range in size from 1/3 ounce of the pygmy squirrel, to 16 1/2 pounds of the
marmots.
Of 8 genera and
68 species found in North America,
seven species are represented in the Appalachian region (Jones' Checklist of North
American Mammals).
EASTERN CHIPMUNK (Tamias
striatus) (treasurer, or storer; striped)
Appalachian
Region Distribution:
Throughout.
Continental Range: Eastern US
and southern Canada. Nine
subspecies are recognized in eastern US,
with three in the Appalachian
region.
Abundance: Common
Population Density: 12 - 24/ acre;
with great annual variation.
Size and Molt: Head and body five
to six inches; 2 ½ - 4 ½ oz. Two
molts.
Mammae: Four pair.
Habitat: Open deciduous forests;
especially rocky areas and forest/field bushy edges.
Active Period: Diurnal, with two
peaks of daily activity, with a midday slump. Inactive in extremes of winter and
summer. Whether chipmunks hibernate or not depends on your source and
definition. They do not develop a layer of brown fat as does a true
hibernator. Instead, they go through periods of torpor of variable length
(rarely more than several days at a time) and frequency, normally starting in
October or early November. Not all animals in a population will
become torpid. During these periods
of torpor, studies reveal chipmunk respiration rates drop from 60 to less than
20 breaths per minute, and temperature drops from 100 to 42 - 45 degrees.
Chipmunks must wake about every two weeks to eat from their caches and defecate.
Will come out in mild weather any time.
(Mammal of Virginia states chipmunks have been seen in Blacksburg, VA
at 15° F and three inches of snow on the ground.)
Individuals vary on length of torpidity, and can change from one year
to the next. Additionally,
those of more northern habitat tend to spend more time “hibernating” while
those of the south enter a torpid state only during severe winter weather.
Diet: Nuts primarily, with a
preference for hickory. Also eats fruit, mushrooms, some invertebrates,
annelids and arthropods (snails, worms, cicadas, and other insects). Chipmunks
spend a lot of time caching food in their burrow, especially during fall. The
food is used during waking time of winter's hibernation. Like the gray
squirrel, the chipmunk disperses its food caches to deal with theft.
It has a primary storage site in its burrow and numerous smaller
scatter hoards well hid throughout its territory.
As other chipmunks raid the primary storage site, the owner will refill
it from the scatter sites. If no
thievery occurs, the scatter hoards often go unused, being left to rot or
sprout. Carries food in its cheek pouches. One chipmunk was found to be
carrying 70 sunflower seeds in its cheek pouches.
Another; 32 beechnuts.
Home Range: ½ - 2 acres,
overlapping with others, with a smaller defended territory. Ranges may shift
annually for food, winter protection, or for finding mates. Males have larger
ranges than females. Within the home range is a protected territory, about 45
feet radius from the burrow opening.
Juveniles typically establish their own burrow systems near their
birthplaces. A PA study found a home
range of .27 acre, with a 0.05 acre range when seeds were ripe. An
Adirondacks report was 0.5 - 1 acre.
Social Structure: Solitary and territorial mammals, although known
to overwinter in small family groups. While ranges overlap, adults will strongly defend its
smaller territory in
order to protect it’s food caches and during breeding time.
There are no lasting pair bonds.
Life Cycle: Under favorable
conditions, two seasonal breeding periods occur; with birthing in April and
July or August, with usually four to five per litter. The second birthing period
often consists of last years' young that failed to breed in the spring,
although a number of chipmunks breed in both spring and summer, unusual in
hibernators. This second birthing period does not appear in northern
populations. Females are in estrus for 3
to 10 days. Gestation period of
31 days, weaned at 5 to 7 weeks, at which time they first leave the nest. At
about 8 weeks, the female refuses to let the young re-enter the burrow and the
young are on their own. This dispersal may be abrupt or take a week or two. At
this time, adults will make continuous "chirps" near their burrows,
perhaps advertising their own territories. Chipmunks can be sexually mature at
approximately three months. However,
most individuals do not breed for the first time until they are one year old.
Life span of two to three years,
although records of up to 13 years in captivity have been recorded .
Dens/Nest: Burrows fall into two categories. They can be simple
with one or two tunnels used for a hideaway or for food storage, or quite extensive with over 100 feet of tunnels
(average is about 12 feet in length) used for nesting and storage. Extensive
tunnel systems include a ten inch diameter nest chamber and separate chambers
for food caches approximately 3 feet underground. Surface opening is often
straight down and 1 1/2 - 2 inches diameter. Openings are often plugged with
soil each night and during the winter. Two side tunnels and openings may
exist, but are often plugged and not used. May occupy the same burrow system
for life. Burrows are not shared except briefly by the mother and young. Tree
cavities are occasionally used.
Tracks: Four front and five hind
toes approximately ½ to 5/8" wide and a long, depending on
depth of imprint. Not common in winter since often will be hibernating.
Straddle is 2 - 3". Holes of 2 inch diameter leading straight down with
no trace of excavated soil is the diagnostic home of the chipmunk.
Scat: Small piles of four to six
rice-sized droppings.
Remarks:
Runs with bushy tail straight up. Perhaps best identified by it’s sharp
chuck-chuck call in the woods as hikers pass. Well-developed cheek pouches
stores have been known to hold up to 32 beechnuts or 70 sunflower seeds. Food caches also are kept
throughout their range. Has been reported to overwinter with rattlesnakes,
purportedly sharing the snake’s warmth. Understandably, the chipmunk enters
the den after the snakes have become torpid, and exit in the early spring,
before the snakes lose their lethargy. However,
chipmunks are a common prey of rattlesnakes.
The name chipmunk is of native Indian origin and probably relates to
its chipping call.
Chipmunks
from western Maryland are paler in color, and those from the Carolinas
brighter than those from other areas. The
darkest individuals are found in the southern mountains, SW VA, Kentucky and
Tennessee. Both albinos and
melanistic individuals are known.
There
are twenty four species of chipmunks in North America (Nowak's Walker's
Mammals of the World - the Checklist of North American Mammals lists 22
species). There is one eastern species and 23 (or 21) western species.
The 1994 edition of Nowak's states the smaller western species and
eastern species were formerly placed in one genus; Tamias,
but recent evidence had caused the western species to be split into a separate
genus, Eutamias. Thus, at that
time, the eastern chipmunk was the only species in the genus Tamias."
However,
the 1999 edition of Nowak has the above two genera combined again
in the same genus; Tamias. It goes further to say, "There is
general agreement that the issue is not settled and further investigation is
needed on chipmunk systematics."
BACK TO THE TOP OF RODENTS
WOODCHUCK
(Marmota monax) (marmot; solitary)
Appalachian
Region Distribution:
Throughout.
Continental Range: Most of Canada and eastern US.
Four recognized subspecies,
with one in the study area.
Abundance: Common; in fact, more
common than in pre-Colombian times.
Population Density: W/H says 1 per
11 acres, occasionally up to 1 per 2 acres. Nowak reports a Wisconsin
average of 1/125 acres. Other sources say 2-6/acres.
Populations tend to vary greatly year to year.
Size and Molt: Head and body 12-20 inches; 5 - 12 pounds.
Hibernation results in the loss of about 30% of fall body weight. However, weight loss immediately after emergence from
hibernation was much greater, with energy derived from remaining stored fat
reserves. Males tend to be
slightly larger than females. One summer molt, taking 3 and ½ weeks,
occurring from late May into September.
Mammae: Four pair.
Habitat: Prefers open fields, but
found in mature woods, pastures and hayfields.
Active Period: Primarily
diurnal to crepuscular (morning and evening, like deer). Only spends one to
three hours above ground each day during the summer. True hibernators, entering their dens in
the first week of November and emerging in early February
(sometimes requiring help for Feb 2). Populations
further to the north may hibernate for up to four months, while more southern
populations may only hibernate for six to eight weeks or not at all.
Winter activity has been documented, but is atypical.
Older and fatter woodchucks enter their hibernacula first and emerge
first.
Diet: Herbivorous grazers.
Seasonal herbs and fruits, but known to taste grasshoppers, beetles and
snails. Does not cache food.
Home Range: 2 - 5 acres. Woodchucks exhibit
little territoriality, except in the direct vicinity of their burrows.
Home range may shift from winter to summer den sites with corresponding shifts
in home range. Same sexes do not generally overlap, but males may overlap 1-3 females. Female ranges are
generally smaller than males in the spring, but may become larger
than males after young are born before contracting again in the fall.
Social Structure: Solitary, but may
live in small family groups with a male dominance hierarchy. Woodchucks are
not territorial, relying on a dominance/submission hierarchy to establish
avoidance of dominants by submissives where home ranges overlap.
Burrows are occupied by a single male, a mother and her young, or
occasionally, a male and a female.
Contrary to other marmots, the woodchuck is fairly aggressive.
This is a function of the length of the growing season.
The shorter growing season of the western marmots (60 days) requires
more time together to assure ample breeding (the Olympic marmot shares its
burrow with an adult male, two adult females and offspring from the previous
two litters). The eastern
woodchuck can afford to be more picky (150 day growing season in PA).
Life Cycle: Mating shortly after
spring emergence (late February to early April), one litter of four to five is produced in
April to mid-May. Gestation period of 32 days. Weaned in six weeks and on
their own (chased off by mommy dearest) at two months of age (July). By
fall, the young have established their own burrows.
Occasional young females will overwinter with the mother, like other
ground squirrels. 10 to 25
percent may reproduce in the subsequent spring at one year of age.
Most will mate in their second or, more commonly, third year. Life span
of four to six years. (Nowak reports 13-15 years).
Den/Nest: Will normally have both a summer and winter den. The
winter den (with normally only one opening) is often situated in brushy or
gently sloping wooded areas, whereas the summer den (with several openings) is in open,
flat fields. Occasionally, the winter den is used year round and by succeeding
generations. The burrow system
includes nest chambers, and/or a hibernaculum chamber (both about 15" wide and
10" high, lined with leaves and grass), and a latrine chamber.
The summer system has a number
of surface openings, easily identified by the excavated soil and a number of
nests. In addition to the main opening, there may be up to five more or less
obvious openings for emergency entrance or exit needs.
At least one of these hidden entrances will be a “plunge hole”;
having a two foot drop from the surface.
Burrows may be four to five feet deep (reportedly up to 16 feet deep)
and 25 to 50 feet long. Other mammals will use woodchuck burrows (skunks, foxes, opossums,
raccoons, rabbits, mice, and others). A
woodchuck burrow can be distinguished from others by the fresh pile of soil at
the main entrance, since woodchucks clean out their burrows several times a
week. Unlike foxes, woodchucks will not defecate outside the
entrance. Rather, they use separate chambers in the burrow.
Tracks: Four toes on front feet, 1
¾" by 2" long, and five hind toes, the front a little longer than
the rear. Running gait shows four
feet tracks within 12" and 12" between sets of prints.
Scat: Quite variable, depending on
diet. Often 2 1/2" long by
1/2" wide. Can be longer
strings (if not separated) or more loose piles.
Fecal pellets are often deposited in a specific fecal chamber
underground or buried in the loose soil excavated outside of the burrow.
This burying behavior is unknown in other squirrels.
Remarks:
The common name comes from the Cree Indian word, wuchak. The largest member of the squirrel family, with a flattened, bushy tail. Also,
the most widely distributed and best known of all the marmots. The only representative of a genus of circumpolar
distribution. An accomplished climber and swimmer. True hibernators, with the
oldest (and fattest) entering the burrow first (late October). In Autumn,
after gaining 30% of it’s summer weight (mostly in the form of a half-inch
layer of brown fat stored over much of the body, especially the back and
shoulders), the ground hog will line it’s hibernaculum with grass and leaves
and then plug the entrances (to maintain constant temperatures and to keep out
curious visitors) before curling into a ball. During hibernation, heart rate
drops from 100 to four beats per minute (W/H says 100 to 15), respiration rate
drops to one breath per three or four minutes, and the body temperature drops
from 98 to about 40 degrees (W/H says 96 to 47). Males usually exit a few days
earlier than females in early March (similar to the hibernating jumping mice)
(W/H says one month earlier). This allows males to compete for good home
range and dominance over other males. The
period of hibernation is about three to four months, with each 10 miles
northward adding one day of hibernation; given similar elevation. Due to the shortened northern growing season, the emergence
is much more precise than in the southern range, thus enabling the well-known
"groundhogs day" of Punxsutawney PA on Feb 2.
In an eight-year period, the PA emergence date fell between January 29
and February 8, regardless of the weather. They will awaken
occasionally throughout the winter (about every two weeks) to defecate. This
may occur in special chambers below ground or, less frequently, on the
surface. They will emerge having lost approximately one half their fall weight
(W/H says 20 to 37%). Ground hogs
have been observed every month of the year, even occasionally with snow on the
ground and temperatures in the 20’s.
Melanistic
(black) or erythristic (reddish-cinnamon) groundhogs are not uncommon. Albinos
are uncommon. Is known to climb trees for fruit and is a good swimmer. It’s
loud, shrill whistle gives it the common name "whistle pig" (call is
made with vocal chords; thus, not truly a whistle). At the beginning of European man's introduction, woodchucks
were scarce. As a result of human
disturbances, the range and population of ground hogs have increased over the
last 200 years.
In
Kentucky, between 1964 and 1971, some 267,500 ground hogs were taken each year!
There
are six other North American species in the genus Marmota,
all located in the west, called marmots.
BACK TO THE TOP OF RODENTS
EASTERN GRAY SQUIRREL (Sciurus
carolinensis) (shadow tail; belonging to Carolina)
ARTICLES
Appalachian
Region Distribution:
Throughout.
Continental Range: East of the Great Plains and south of the Great
Lakes. Basically, their range correlates with the eastern hardwood forests.
Five subspecies recognized
in eastern US, with only one in the study area.
Abundance: Common at lower
elevations; rare at higher elevations. Populations reflect "mast"
years (acorn supply). Much
higher numbers were found when the native American chestnut tree was common.
Population
Density: Highly variable, with highest populations in late August and
September. Chapman and Feldhamer report
four WVA state forest densities over a six year period ranging from 0.44-1.0,
0.24-0.84, 0.2-0.44, and 0.32-1.4 per acre. Our friend, Dr. Vagn Flyger of Silver
Spring, MD, found a range in his suburban yard backing up to the Northwest
Branch in Quaint Acres from 0.8-4.0 per acre over a three year
period. 2-20/acre in some studies,
others report 0.1-6/acre; max up to
20 / acre (public park densities can exceed 50 per acre).
Size and Molt: Head and body is 9 to11 inches; ¾ - 1 ¾ pounds. Sexes are alike in size and color. Two molts; paler winter pelage, although the tail
molts only once in mid summer. Northern
individuals are larger than southern populations.
Mammae: Four pair.
Habitat: Mature oak and hickory
hardwood forests. Land use may be highest in forested river bottomlands, river valleys and swamp hardwoods.
Extremely adaptable, they are found anywhere, except
spruce/fir forests, where red squirrels dominate. Gray squirrels tend to prefer more dense woods than fox
squirrels. The more large trees
an area has, the more gray squirrels will inhabit the area (larger cavities
and more food).
Active Period: Diurnal in winter to
crepuscular in summer, non-hibernating, primarily arboreal mammals.
Active year-round, but will will remain in their nests in very cold or
stormy weather until food forces them out. W/H states that females are more active in spring and summer, with
males being more active in autumn and winter. Most active in September and early October, burying
acorns (this is also the peak time for their arboreal activity).
Additionally, spring born (and some adult) fox and gray squirrels
frequently move to new locations at this time.
This dispersal period is also referred to as the “fall reshuffle”,
with movement of 6 or more miles. As
noted in the remarks below, this fall reshuffle, in conjunction with a failed
hard mast season, can result in massive fall migrations, more appropriately
called movements.
Diet: Nuts are the mainstay, with
buds, flowers, and roots in spring; maple samaras, fruits, berries, mushrooms,
and insects in the summer; nuts and fungi in fall and winter (specifically oak
and hickory nuts and maple samaras). They usually feed on just one food at a
time, changing the item as additional sources come along. They are known to eat bark of dead trees
for the fungal mycelia within. Shedd
even notes gray squirrels are known to eat bird eggs and frogs.
In February and March, they chew twigs of maples, oaks and pine. Winter
food storages, or caches, consists of each acorn buried separately, decreasing
the risk of losing an entire stash. Adults obtain minerals from bones, antlers and turtle shells.
See
Articles
above for more information.
Home Range: Most studies indicate
one to four acres, up to ten acres (varies with food availability), larger for
males than females. Chapman and
Feldhammer report 2 acres for males and 1.25 acres for females in a Maryland
study (Flyger). Nowak reports 1.3 acres for males and 1 acre for females in a Virginia study. Male home
range will overlap that of several females. Overlaps
other squirrel home range. Range
of gray squirrels are smaller than the fox squirrel.
Basically, their home range focuses on (and around) one nest tree, shifting
as food sources become available.
Social Structure: Usually solitary,
shy and non-aggressive. During the mating season, males will be territorial and exhibit
antagonism toward one another. Males are polygamous.
The
same applies to females on a nest. The
male provides no parental care. Mammals
of Virginia say gray squirrels are gregarious and often congregate in
considerable numbers, while W/H says they are not social, only gathering
in winter denning situations..
Chapman and Feldhamer says
both fox and gray are relatively nonaggressive toward either their own species
or the other species, but may share dens with a number of individuals of their
own species (Shedd says only males and juveniles will den together in winter,
with females – probably pregnant - being cantankerous and denning by
themselves). Wilson says at night
and during bad weather, as many as seven or eight squirrels may occupy a
communal den, where they will groom each other and conserve heat during cold
winter nights. Among squirrels
with overlapping home range, especially at high densities, there is an
established dominance hierarchy, with the oldest (male or female) normally
assuming dominance (W/H says males over females, adults over juveniles, and
residents over immigrants). Dominance
(i.e., aggression) appears at mating time, food concentrations (including bird
feeders), and at den trees.
Life Cycle: Normally two litters of
about three (1-9) per litter per year (parturition about March and August).
Forsyth says only 20 to 40% have two litters.
Gestation period of 45 days, weaned in two months; about the same time
they first leave the nest. Breeding
can begin as early as December. Males
play no role in child-rearing. The
spring brood stays with the mother until late summer, and the second brood
will often stay with the mother over winter. Young make leaf nests at about 18
weeks of age. Young breed the
next year (may only have one litter). Life span has been
up to 15 years, although 6 years is more the maximum. Wilson says
more like one year for the average. One captured animal lived for 23
years.
Dens/Nest: Winter and summer nests are
made. Will make winter nests in
tree cavities and summer leaf nests in branches (occasionally a winter leaf
nest is maintained). A favored den tree may be
used for many years, but an animal always has several other nests where it can
escape enemies. The tree cavity must be 12 inches deep and have an
opening at least 3 inches in diameter. Often, several leaf nests
(called dreys) are built around
different food sources. Gray squirrels average 1 1/2 to 2 leaf nests per
squirrel. The leafy nest is composed of leaves and twigs forming a
water-resistant form lined on the inside with moss, grass, and shredded bark.
The main entrance is positioned to face the main tree trunk.
The winter nest is high off the ground in a tree hollow, lined with
vegetation. Normally, the first brood is had in the tree cavity with the
second brood in a leaf nest.
Tracks:
Has five toes on hind feet (2 5/8" l x 1 1/4" w) and four on the
front feet ( 2" l x 3/8" w). Straddle
is 4 to 5". Running stride of 16 - 36". Front and rear tracks
are often lined like a square, so it can give the appearance of two question
marks (!!), with the front tracks behind the rear tracks (or somewhat behind
and between the rear tracks) .
Scat: Pea-sized droppings (1/4 –
3/8” x 3/16”).
Remarks:
Can be blonde, black (melanistic), erythristic (reddish), or albinos (Olney,
IL is famous for its protected albinos - Trenton, NJ and Greenwood, SC also
have albino populations). Black squirrels are more common in
the northern portions of their range. Gray
squirrels from MD and the western parts of VA and NC are slightly darker and
larger than those from eastern VA and most of the Carolinas. It is common for
one of the color variants to be dominant in an urban setting, since the
predatory natural selection (culling out) of these colored aberrants does not
exist.
Melanistic
gray squirrels of the Washington DC area owe their existence to two shipments
of black squirrels from Ontario being released in the National Zoological Park
in 1906. It appears that the dark
pelage gives them an advantage over the gray winter coats of the normal
squirrels in winter through energy savings due to the additional absorbed
solar heat (lower heat loss and lower basal metabolic rates).
Formerly
known to make massive movements in search of food. Ernest Thompson Seton estimated one mass movement at more
than one billion individuals in 1920.
Such migrations are necessitated by local high populations and erratic
annual acorn mast crops. A more
recent mass movements on a reduced scale was reported in October of 1968 in the southern
Appalachians of TN, GE and NC. This followed a
mast crop the previous year, resulting in
an abundance of young squirrels. Unfortunately,
1968 was a poor mast year, resulting in a major food shortage.
Such a phenomenon is incorrectly called a migration, when it actually
is nothing more than a big fall reshuffle.
Caching of seeds and nuts ensure tree generation. Nuts are buried
separately, about 1/4" to an inch deep and are recovered by any squirrel that may
smell them (one study found 85% of buried nuts were found over the winter).
Nuts buried by scientists were recovered at the same rate as nuts buried by the
squirrels, indicating that memory is not involved in nut recovery. The
nuts can be smelled when buried under a foot of snow. A
thicker pelage and layer of fat help insulate the squirrel in winter. While
fox squirrels and gray squirrels inhabit similar habitats and share common
foods, they are rarely found in the same area (mutually exclusive, or
allopatric) and do not interbreed. Fox squirrels prefer the more open woods,
the gray squirrels in the more dense woods. When 10% of the land is wooded,
both species seem to be equally abundant.
When 70% of the land is wooded, fox squirrels are absent.
Gray squirrels are a major prey species of timber rattlesnakes. In the
late summer, swellings under the skin are signs of the developing larvae of
the parasitic botfly, which emerges in the fall. They do not seriously
endanger the squirrel.
Due
to the extraordinary amount of tannins in their systems afforded the gray and
fox squirrels by their acorn digestion, they are unusual in rarely having
either tapeworms or roundworms, which is a deadly poison to these parasites.
Much
more abundant a century ago. Gypsy
moth defoliation and subsequent loss of acorns in the 1980's practically wiped
out squirrel populations in southern PA.
Important
game species with 40 million "harvested" each year in the US.
In
Kentucky, an average of 1,309,000 gray and fox squirrels were taken annually
from 1964 to 1971.
There
are seven species of the genus Sciurus
in North America.
BACK TO THE TOP OF RODENTS
EASTERN FOX SQUIRREL (Sciurus
niger) (shadow tail; dark)
Appalachian
Region Distribution:
Throughout.
Continental Range: East of the
Great Plains and from PA south. The
range extends slightly farther west than that of the gray squirrel but not as
far northward. W/H says to the west
of a line from Harrisburg PA, Harpers Ferry WV, Roanoke VA, and along the Blue
Ridge to the Smokies, with a disjunct subspecies found on the eastern shore,
although other sources show the fox squirrel ranging throughout all SE
US. However, declining populations
are found in the piedmont and coastal plains regions of both Virginia and
North Carolina. Eight
subspecies recognized in the eastern US,
with two subspecies found in the study area..
(The well-known federally-designated endangered species, the Delmarva fox
squirrel; Sciurus niger cinereus, is one of these eight subspecies. It
is only found on the Delmarva peninsula of Virginia and Maryland.)
Abundance: Uncommon in central
PA and the piedmont and mainland coastal plain of VA and NC, common to the
west of these locations, but with declining numbers. Due to the decrease in the open, mature forest habitat in the east
preferred by fox squirrels, their numbers are declining and often confined to
small and shrinking localities.
Population Density: Highly
variable. Reported densities of 0.4 -
2/acre, up to
nearly 10 per acre. Weigl, working with piedmont and coastal plain
populations in North
Carolina, found densities averaging 0.002/acre.
Size and Molt: Head and body 10 to
15 inches; 1 ¼ - 3 pounds. (Weigl's
NC piedmont and coastal plain populations averaged 2.2 lbs.) Sexes are alike in size and color. Largest
tree squirrel in the Western Hemisphere.
Chapman and Feldhamer
says two molts, with one tail molt. Nowak says there are two
molts per year in some, perhaps all, species (of the scuirus genus), but
the tail fur is shed only once yearly. W/H, PA Mammals, says one molt in late spring.
Twice the size of
gray squirrels.
Mammae: Four pair.
Habitat: Fox squirrels prefer
higher ground and larger trees than gray squirrels.
Open hardwood forests and pine woods where occasional fires promote
grassy surface growth are ideal. Will not be found in the closed forests of
the gray squirrel.
Active Period: Crepuscular in
summer, diurnal in winter; non-hibernating, they start foraging later in the
morning than gray squirrels. Tends to aestivate (summer dormancy) in summer if
hot. Most active in summer in
light rain or just after rains (cooler temperatures, nuts and fungi are easier
to smell, and the ground is easier to dig).
Most active in September and early October, burying acorns.
Additionally, fox and gray squirrels frequently move to new locations
at this time. This dispersal
period is also referred to as the “fall reshuffle”, with movement of over
6 or more miles. However, mass movements by fox squirrels have never
been as massive as gray squirrels.
Diet: No apparent difference is
observed between the gray and fox squirrels.
Preference is for hickory and oak acorns. Pine seeds from cones; green or mature and the cambium tree
layer are preferred in some habitats. Also buds and berries, fungi, insects,
bird eggs, and corn. Nuts and
seeds are buried individually or two or three together like gray squirrels,
versus the caching done by red squirrels.
Early summer may be the hardest time for fox squirrels to find food,
especially in pine forests. The
buds, flowers and young fruits of tulip trees are heavily foraged when
available. Studies on recovery of
cached acorns reveal tremendous range from 33% to 99%. Succulent vegetation will normally satisfy their moisture requirements. Water is utilized if present, but the lack of it
is not a limiting factor.
Home Range: Varies by densities,
food supplies, and habitat quality. 7
- 24 acres and greater are commonly reported.
Weigl's NC piedmont and coastal plains populations had home ranges estimates
of 66 and 42 acres, or 107 and 62 acres, respectively for males and
females. A study of a Florida population revealed a home range of
106 and 41 acres for males and females. This is larger than the gray squirrel,
not just due to size, but also the relative paucity of food in the preferred
more open woods habitat. Home
range may overlap.
Social Structure: Solitary, except
occasionally to feed in common areas and share winter dens among family
members.
Life Cycle: Similar to gray
squirrels (but breeds slightly earlier), with two litters (from two year olds)
with an average of two or three (1-6) per litter per year. (Weigl's NC
piedmont and coastal plain populations revealed no evidence of two litters per
year.) If a female produces 2 litters per year, they may produce none the next year if food conditions are bad.
Birthing usually occurs
in March and again in July, although pregnant
females have been found every month of the year. Weaned, able to eat solid food in eight weeks, and soon
thereafter are independent. Gestation
of 44 days. Sexual maturity in
one year (first year females usually having only one brood). Will
disperse a distance of 9 miles or more from their birthing site. Life span up to
12 years.
Dens/Nest: Prefers hollows in trees for
winter and natal nests, but will make large leaf nests in summer (and winter
if tree cavities are scarce). Cavity openings are 3 inches wide with a hollow
of six inches wide by sixteen inches deep. Outside leaf nests vary greatly,
averaging 20 inches in diameter. Like gray squirrels, the opening faces the
trunk. Winter nests have an outer layer of twigs with leaves attached, a
series of inner layers of damp leaves pressed together, with a lining of
shredded bark and leaf fragments. A
leaf nest may be used for several years.
Fox squirrels average about three to six active leaf nests per
individual (one study reported in Nowak found an average of nine nests were
used per year). Platforms, made just
for sitting, are sometimes made.
Tracks: Four-toed front feet are 1
and 1/2" and five-toed rear feet are 2" in length.
While running/hopping, the front foot prints are parallel and behind
the rear feet. Straddle is 4
1/2" with 2' stride. Food debris is often found scattered about the
base of a tree used as a feeding perch by fox squirrels.
Scat: Pea-sized droppings.
Remarks:
Fox squirrels get their common name from their fox-like tails.
Species name comes from southern
subspecies, which is much darker than other regional populations.
The
populations of the Appalachians and to the west differ from the eastern
populations in being smaller (~2 lbs) and more consistently reddish in
color. The eastern populations of the piedmont and coastal plains
averaged more like 3 pounds in size and were quite variable in coloration,
being silver, gray, black and gold, often with black masks and with distinct
white marking on the nose, ears, and feet. Additionally, western
populations inhabited deciduous forests while the eastern populations occupied
mature pine-oak woodlands. Weigl and others suggest that the
southeastern and western fox squirrel populations evolved in isolation in
separate refugia during the Pleistocene, eventually colonizing different
regions to the north and subsequently establishing variable zones of overlap
and interbreeding.
Fox
squirrels have the widest range of colors of any other mammal. Fox squirrels can be found in several dorsal (back) color
morphs (subspecies); brown, brownish orange, gray-black, blackish brown, steel
gray, or all black (color variations tend to match local habitat - yellow
midwestern squirrels blend with the yellows of the hickories in fall, black of
southeastern squirrels match periodic burning of the pine forests, etc.- its
just someones' thought). Along the coastal area of Virginia and Delaware (S.
niger cinereus) the population is colored steel gray with no tawny. The
ventral (belly) can also vary from creamy yellow to rusty orange to black.
Fox
squirrels have a darker head (than gray squirrels), some white on the muzzle
and white on the back of the ears, and a larger, more fluffy tail than the
gray squirrel.
More
terrestrial than gray squirrels (less agile in trees than gray squirrels).
Fox squirrels spend more time foraging and running about on the ground
than do gray squirrels and will more often run on the ground between trees
while grays will jump from one tree branch to another tree branch.
Wilson says fox squirrels are more “easy going”, getting up later
in the morning and turning in earlier in the evening.
Fox squirrels have home ranges of up to ten times the size of grays,
due to the more open (poorer food supply) habitat.
Fox
squirrel bones are pink (due to the accumulation of porphyrin compounds); gray
squirrel bones are white. Of the three tree squirrels, the fox is the
quietest, the gray more vocal, the red squirrel, the most vocal. Mass
movements, well-documented among gray squirrels, are not common, nor as large,
among the fox squirrels.
Due
to the extraordinary amount of tannins in their systems afforded the gray and
fox squirrels by their acorn digestion, which is a deadly poison to tapeworms or
roundworms, they are unusual in rarely having
either of these parasites.
An
account by Seton (1953) states; Arlington
Cemetery had always been a haven of fox-squirrels. About 20 years ago, they had increased to surprising numbers.
Then one day, they seemed to be possessed of a migration craze; they
all set out eastward. At once,
they were met by the broad Potomac; but plunged in, swimming away toward
Analostan Island (Roosevelt Island), the nearest wooded tract.
Here many of them stayed; but many moved on, and were lost sight of. They still frequent Arlington Cemetery.
Approximately
18 Fox-squirrels
were released in the National Zoological Park from 1899 to 1916 from various
states across the country (see remarks for gray squirrels above).
When Audubon and Bachman were conducting their research
for the Quadrapeds
of North America, they noted that in South Carolina the fox squirrel
"takes possession of the deserted hole of the ivory-billed
woodpecker."
In
Kentucky, an average of 1,309,000 gray and fox squirrels were taken annually
from 1964 to 1971.
There
are five species of the genus Sciurus
in North America.
BACK TO THE TOP OF RODENTS
RED SQUIRREL (Tamiasciurus hudsonicus) (steward, shade tail; the Hudson Bay)
Appalachian
Region Distribution:
Throughout.
Continental Range: A boreal
species of the north across Canada, south along the Rockies to southern
Arizona and New Mexico, and down the Appalachians to Smokies.
Five subspecies recognized in
eastern US,
with two found in the study area. In fact, one of
the widest distributions of any North American squirrel.
Abundance: Common, especially in
conifer forests.
Population Density: 1-3 / acre. W/H
says up to18 per acre with great seasonal variability.
Wilson notes up to 17 – 20 per acre is possible in good habitat. Nowak reports
from 2 - 11 per acre. Population densities reach a high every three to
four years in the Adirondacks of New York.
Size and Molt: Head and body 7 to 9
inches; 5
to 9
oz. No differences in size or color by sex. Two molts,
although, the tail only molts once in the middle of summer.
Mammae: Four pair.
Habitat: Highly arboreal.
Apparently, it originated in coniferous forests, but now is found also
in mixed hardwood forests and swamps of higher elevations.
In southern limits of its range (southern Appalachians), the red
squirrel is found in the same areas as gray and fox squirrels, with resultant
competition for food and den sites.
Active Period: Diurnal in winter,
crepuscular in summer, spending much time on the ground as well as arboreally;
year-around. Red squirrels do not hibernate, but may spend several days
in their dens during inclement winter weather.
Diet: Quite diverse diet (more
omnivorous than the gray squirrel). Due
to high metabolism, a high energy content diet is required.
Some brown fat is present in winter. Most of the energy is derived from the hemlock, pine and other conifer
cones, which are stored in mass food caches ("middens") if not eaten on the spot. Also acorns, hickory and
beechnuts, tulip tree and sycamore seeds, when seasonally available, buds,
twigs, occasional insects and mushrooms (including the very poisonous amanita;
aka, destroying angel or fly agaric). In
the Smokies, fruits of the cucumber magnolia, mountain holly, silverbell,
beech, buckeye, serviceberry, black walnut, American chestnut, and blackberry;
seeds of mountain maples, hemlock, and pines; cones of fir and spruce;
mushrooms; the buds of the rosebay rhododendron and the buckeye and roadside
garbage cans are eaten. Fungi are
cut and placed in trees to dry for later winter eating, or later cached in
middens. Terminal evergreen buds are a main stay in winter diets. Have been known to eat young birds and bird eggs.
Unlike the single nut burial philosophy of the gray and fox squirrels,
the red squirrel goes for middens, used for
winter food, which is vigorously defended. These middens (made up primarily of
pine cones) may grow over the years to amass several bushels of nuts. Red
squirrels can afford to make this middens where they only have other red
squirrels to defend against. However,
in regions cohabited with gray squirrels, red squirrels must scatter their
hordes, since gray squirrels are not intimidated by red squirrels’ threats.
Hole eaten into nut is irregular in shape. They have favorite feeding sites, as opposed to gray
squirrels, that pretty much eat their acorns where they find them.
The size of this debris pile is measured in bushels and varies with conifer species, seeds, proportion of diet, forest age, squirrel population and the feeding place,
but can be up to 20 feet by 12 feet and 3 feet deep. Red squirrels are also known to "tap" maple trees for sap.
Home Range: 2 - 5 acres, with no overlap of range (unlike
gray squirrels), but only 0.5 to 3 acres defended in
the area of the nest and prime feeding areas.
In high quality habitat, red squirrels have been observed to be
non-territorial.
Social Structure: Solitary. Very
territorial and aggressive in protecting their core home range (1/2 to 2
acres), especially in late summer when juveniles are dispersing. Females allow
males into their territories in late winter for mating.
Not known for communal denning in winter like gray squirrels.
Life Cycle: One or two litters per
year (April - May) with an average of five or six (1-7) per litter. Females are
receptive for only one day, at which time, she allows males to enter her
territory. Gestation period of 35
days. A second litter is had in August in good seasons. Weaning at 9 - 11 weeks
of age (W/H says 6 to 7 weeks, Novak says 7 - 8 weeks). (PA mammals says weaning occurs after the
female makes a nest on the periphery of her range for her young. W/H says the
female is known to occasionally leave the area to the young, who then
subdivide it.) Spring young disperse at
around 18 weeks (September). Second brood
overwinters with the mother. Young are sexually mature the following season.
Life span two or
three years common, with ten years known in captivity. Only 5% of a
cohort live beyond five years.
Dens/Nest: A winter and summer nest is
common. Tree cavities are preferred for winter nests, while leaf nests
(~15 feet high) in summer are common (about the size of a basketball, often
made of grapevine bark, while gray
squirrel nests are larger and coarser), especially in conifer woods, where
cavities are less numerous. Will also
build on abandoned bird nests or make use of underground dens. Often, a
second winter nest is made in the form of a weather-tight structure located in
the densest foliage of a tree. Can
tunnel and make nests in the ground under rocks or stumps in the winter. Burrow holes are 2 ½ to 3
inches in diameter, often with cone remains near the entrance.
Tracks: Four front toes (1/2"
l x 3/8" w) and five rear toes (7/8" l x 5/8"w). Straddle
is 3 to 4". Running stride
is 9 - 30". In winter, makes
extensive runways through the snow.
Scat: Small, 1/4" - 1/2"
elongated droppings.
Remarks:
Known in WV as the "fairy diddle".
A northern species, the red squirrel is smaller than the gray squirrel,
with somewhat different summer and winter pelages. In summer, a lateral black
stripe separates the dorsal brown from the white ventral fur. In the winter,
although the black stripe disappears, the back and tail is rusty red and tufts
of hair appear on the ears. Red squirrels are distinctly darker on the head
and sides in the spruce and fir forests of the higher southern Allegheny
Mountains. Both albinism and melanism is
known among red squirrels. Very vocal and active;
usually heard before seen. Smaller than the gray and fox squirrels. Vocally
protects it’s territory, many hunters have had their hiding place announced
by the red squirrel. Noted for
its food caches, which may accumulate in size over several years, usually
located in hollow trees. The seed caches (middens) are favorite sources of
high quality seed used by foresters, which are cleaned and used in nursery
propagation.
Hickory
nuts eaten by red squirrels will have a ragged hole opening. Flying
squirrels have smooth edges of the opening, while white-footed and deer mice
will have several openings. Gray and fox squirrels crush the nut.
The
western Douglas squirrel is the only other species of this genus in North
America. Both species are known as pine squirrel, mountain boomer,
chickaree, or fairydiddle.
Several
million red squirrels are trapped each year for the fur trade.
BACK TO THE TOP OF RODENTS
NORTHERN
FLYING SQUIRREL
(Glaucomys sabrinus) (gray, mouse;
Severn River)
Appalachian
Region Distribution:
High elevations (> 2,680') of the Appalachian Mtns. as far south as the Smokies. Can be
found continuously from Maine to central PA.
South of central PA, only two disjunct relic populations exists. Both, by their isolation, are recognized as
subspecies and designated as Federally listed Endangered Species.
In six eastern WV counties (Greenbrier, Pendleton, Pocahontas,
Randolph, Tucker and Webster) and Highland County, VA, the subspecies Glaucomys
sabrinus fuscus was first described in 1936.
The type locality is Mill Point, Cranberry River, Pocahontas County.
The second subspecies, Glaucomys
sabrinus coloratus, first described in 1953, is found in SW Virginia near Mount
Rogers, VA (Whitetop Mountain) and along the Appalachian Mountains of the
North Carolina/Tennessee border through the Smokies as far south as
Georgia. Populations identified
for study by Weigl included Roan Mountain, Bald Knob Ridge, Grandfather
Mountain, the Black Mountains (including Craggy Mountains), and the Great
Smoky Mountains, among others. For the first
time since 1958, three northern flying squirrels were found in the Smokies in
1987 on Clingman's Dome. The type locality is Bald Knob, 5,000 feet south of the summit, Mt.
Mitchell, NC.
Continental
Range: Throughout Canada, extending south along the Rockies and the
Appalachians. Four
subspecies recognized in eastern US, with
the two Endangered Species
mentioned above
and a third found in PA making up the population of the Appalachian region.
Abundance: Becoming rare - listed federally as Endangered in VA, NC and WV.
In WV, the characteristic spruce-fir and northern hardwood habitat of
the G. s. fuscus subspecies is relatively abundant, potentially more
continuous and at lower elevations, thus suggesting some potential for
sustained populations. The subspecies G. s. coloratus, resides
only on high elevation ridges and peaks, and thus occupies habitat islands
which are both highly disjunct and of limited size.
It is very limited from southern Virginia to the Smokies due to the more
aggressive southern flying squirrel (and, to some degree, a parasite that is
transmitted by the southern flying squirrel).
This limited range, along with the possible impact of warming trends, recent
droughts and high elevation loss of conifers from introduced insects and
acid-rain impacts, suggests a more vulnerable status of this southern
subspecies. These disjunct populations are relics of former
broader populations that existed in historically cooler climatic conditions.
Populations have been shown to fluctuate, with peaks reached in the late
1980's in areas studied in WV, VA and NC.
Population Density: <1 to 4/acre.
Size and Molt: Head and body 5
½ to 6 2/5 inches; 2 - 4 ½ oz.
(Weigl's study populations in NC and TN had a mean head and body length of
6" and weight of 3.85 oz. These are the subspecies G. s.
coloratus.) Females are generally larger than males. The
northern flying squirrel is slightly
larger than the southern flying squirrel. (In addition, the northern subspecies, G.
s fuscus, is smaller with a more muted pelage than the southern
subspecies, G. s. coloratus. One
molt. Shedd says two molts, unlike the southern flying squirrel.
Shedd also says the northern’s tail molts only once, like the gray,
red and southern flying squirrel.
Mammae: Four pair.
Habitat: In the southern
Appalachians, a mixed ecotone of dense coniferous forests and northern hardwood
forests (birch/beech/maple/cherry) are favored habitat. The WV
subspecies (G. s. fuscus) is generally limited to habitat over 3,000',
while the more southern G. s. coloratus is most commonly found at
elevations over 4,500'. Habitat in this Appalachian region is limited by
extent of spruce forests and competition with the
southern flying squirrel. See remarks below.
Active Period: Nocturnal, primarily
in the evening and just before sunrise. Active year-round.
It is known to withstand cold and wet conditions lethal to red squirrels and
southern flying squirrels. Has been found foraging on the forest floor even to -24
°
F (Weigl reports -4° F). However,
Weigl found that when inactive and exposed to cold temperatures, the northern
flying squirrel will drop it's temperature from ~98 to 86° F and assume a
curled position. Red squirrels under similar conditions are not able to
reduce their body temperatures, and thus are not able to survive similar
conditions without adequate store. Southern flying squirrels show an
intermediate response, with a slightly reduced metabolism and body
temperature. Weigl notes this reduced metabolism and body temperature is
not torpor, since the northern flying squirrel is capable of immediate
activity at these reduced levels.
Diet: Somewhat more omnivorous than
the southern flying squirrel. Lichens
and fungi, including mycorrhizal fungi (which is a major source of minerals,
such as sodium and phosphorus, as well as energy), can constitute a major part of their
diet . The staminate cones of conifers
are a major part of the spring diet. Nuts are eaten, however,
less so than the southern flying squirrel due to the absence of oaks and
hickories in its range. Also eats buds, fruit, various seeds and a number of
insects (beetles and moths). They are known to raid the middens of nocturnal
red squirrels during the night. Will
eat meat (young rodents, birds and bird eggs, but less than southern flying
squirrel); are known for stealing bait. Creation of food caches in the summer
for winter use is contradicted by various authors (as a minimum, the behavior
is not as common as with the southern flying squirrel). It has been
found that many of the mycorrhizal forms of fungi that provide food for the
forest trees, depend on the dispersal of fungal spores through the defecation
of these squirrels. In fact, a northern California study
correlated the fungal biomass positively with the numbers of northern flying
squirrels.
Home Range: 2 ½ - 7 ½ acres. (W/H
says 5 - 19 acres or more.) One North Carolina/ Pennsylvania study
reported a home range of about 5 acres. Weigl's North Carolina work
found ten squirrels had a mean of 23 acres, with a winter range of 29 acres
and a summer range of 15 acres, possibly a function of remote conifer food
sources and mate-finding scenarios.
Social Structure: Very gregarious,
although not as much so as the southern flying squirrel.
Weigl's study found 33 instances of nest sharing, averaging 2.8 per
nest (2-6). Most groups consisted of
only two individuals (13 out of 33) and 15 groups were composed of adults of
both sexes. About equal numbers of all male or all females groups (7 and
4 respectively) were observed. In groups of three or more involving
juveniles, the adult was always a female. Males do not help in child care.
Life Cycle: Usually one litter with
two or four (1-6) per litter per year.
Parturition from April through September, after a gestation period of 37 - 40 days. Weaned
in eight to nine weeks, often spending the first winter with the mother,
normally breeding the following spring. Life
span 3 to 5 years, with 13-14 years in captivity.
Den/Nest: Prefers woodpecker holes or
tree cavities, although even witch’s brooms and mats of moss have been used
in northern regions. Will also use leaf nests (dreys) in spruce trees. (Being larger than the southern flying squirrel, it must make more
leaf nests, since less suitable trees can be found.) Also uses old crow or red squirrel nests.
Weigl found 12 summer nests included 7 cavities and 5 dreys, with 27 winter
nests including 15 cavities and 12 dreys. Urban (1988) found an almost
exclusive reliance on drey nests in WV. Nests are covered with
firmly matted spruce twigs, lined with shredded yellow birch bark, lichens, grasses,
sedges, and moss. Outside nests
are 8" - 10" in diameter, and 6" - 8" deep, usually high
(14-28') in red spruce (exclusively spruce for Weigl's study). A single
2" opening leads to the nest. Weigl found an average of 3.25 nests per squirrel were used. 70% of
Weigl's nests were found within 300' of the coniferous/hardwood borders.
A third category of nest is recognized as a retreat nest, of marginal nest quality and
serving as sheltered breeding stations, food storage areas or defecatoria.
Tracks: The give away is the
"sitzmark", or landing spot, with the pattern of feet leaving the
site, much like a gray squirrel, only smaller (rear foot 1 5/8" in
length, with a straddle of 3 3/4 inches).
Scat: Indistinct piles, each
dropping less than 1/4" in length.
Remarks:
The northern and southern flying squirrels are the only two species in the
genus. The northern flying squirrel is much larger and heavily built than the southern flying squirrel. Belly hairs
basically white with gray at the base (but occasionally white throughout),
while the southern flying squirrel belly hairs are a solid white. Individuals from the southern Appalachians tend to be darker than northern
individuals. Mean average glide is 66 feet, although flights up to 270 feet
are recorded (the distance is more a function of height; the glide course is
about three horizontal feet for every vertical foot drop).
Their tail allows them a good deal of maneuverability.
In fact, flying squirrels have been observed turning more than 180°
during a glide. Less vocal
than the southern flying squirrel.
The
northern and southern flying squirrel are generally not sympatric (occurring in the same area;
thus, they are allopatric); the smaller southern flying squirrel being more
aggressive and tending to displace the larger northern flying squirrel.
Where they overlap, populations of both are limited and unstable.
Overlap areas generally support one species or the other. However, where
there are good populations of the northern flying squirrel, red squirrel
populations are almost always abundant. There is also evidence of a nematode parasite of the southern flying squirrel
that is lethal or debilitating to the northern flying squirrel. When
northern flying squirrels come down from their mountain habitats and come into
contact with the southern flying squirrel, it would very likely pick up the
parasite and perhaps suffer either sickness or at least a competitive
disadvantage. On the other hand, when southern flying squirrel
populations invade the spruce forest habitats of the northern flying squirrel,
it cannot store adequate winter reserves of acorns to enable it to
competitively survive the winters. Still, another factor comes into play
regarding the nematode. The staminate spruce cones that make up a
significant portion of the northern flying squirrel's spring diet are filled
with highly aromatic oils that are known to have some potential as "vermifuges".
It is possible that these cones provide the northern flying squirrel with some
protection in the high elevation spruce forests which is lost when it leaves
the coniferous forests for the lower elevation oak forests.
Interestingly, it has also been found that the success of the nematode is
severely limited at colder temperatures.
With
southern flying squirrels found at the highest elevations in Virginia, it does
not look good for the future of the northern flying squirrel in
Virginia.
The introduced balsam
wooly adelgid will have a major impact on these squirrels by the loss of the
nesting sites and food source. High
concentrations of heavy metals found at high elevations in NC (lead, copper,
zinc, manganese) can also be harmful to these squirrels.
At
night, the eyes of the flying squirrel will shine red by the light of a
flashlight.
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SOUTHERN
FLYING SQUIRREL
(Glaucomys volans) (gray, mouse;
flying)
Appalachian
Region Distribution:
Throughout.
Continental Range: All of eastern US. Three eastern subspecies recognized in eastern US, with
only one in the Appalachian region.
Abundance: Common wherever there
are oak/hickory forests. In fact,
often outnumbers the diurnal gray squirrel in mature woodlands.
Population Density: 1-3/acre, up to
5/acre.
Size and Molt: Head
and body 5 ½ to 5 2/3 inches; 1 - 3 oz.
One fall molt. Females are generally larger than
males. Smaller than the
northern flying squirrel.
Mammae: Four pair.
Habitat: Prefers mature hardwood
forests, as opposed to the preferred coniferous forest of the northern flying
squirrel, since they rely on stored middens of acorns, unlike the northern
flying squirrel.
Active Period: Nocturnal. Does not
hibernate, but undergoes periods of torpor and inactivity, more often than the northern flying
squirrel (who, apparently, is more used to the cold weather). NAS says body
temperatures can drop to 22°F and will take up to 40 minutes to wake. Tends to aggregate in winter nests (in one study of 841 winter
nests, 676 - 81% - had two or more in the nest, and, of those, 79% housed only
adults). 16 were found curled
together in a wood duck box one February day at the Patuxent Research Refuge
in Maryland (50 have been recorded in one nest).
Low body temperatures seem to coincide with larger denning numbers.
Diet: Most carnivorous member of
the squirrel family; eating insects, birds, eggs, small mice and shrews, and
even carrion. Animal sources dominate summer diet. Winter and spring diet
includes buds, catkins, and shoots of trees.
Also mushrooms, berries, buds and maple sap. Forages mainly arboreally.
Known to cache food (unlike the scurids, this squirrel hides its nuts above
ground in tree hollows. The southern flying squirrel may store up to 15,000
nuts in a season. Hole eaten in nut is circular with a smooth edge. (It
is a single hole versus numerous smaller holes of the mouse.)
Home Range: 1 - 7 acres.
Females are territorial in summer.
Males are less territorial, with broadly overlapping ranges. A
Maryland study a home range of 6 acres for males, 5 acres for females and 1.5
acres for juveniles. Ranges of males overlapped extensively, with
females overlapping very little with other females or males.
Social Structure: Somewhat
gregarious, especially in winter nests. Very
shy. Males overlap ranges extensively, but females ranges overlapped
little among themselves or with male ranges during the breeding
period. Reports vary on male role in rearing young; one says they help raise
young, SE Mammals says male kicked out at child birth; raised by the mother,
then male reappears for second mating when young are weaned, others make no
comment about male role. Gregarious in winter months, with usually three to
eight sleeping in the same cavity (although 28 and 50 – in an Illinois tree
hollow - have been recorded). Shedd
states the southern flying squirrel is considerably more aggressive than the
northern, and generally is dominant where the two species are sympatric.
Life
Cycle: Usually two litters, with two to four per litter per year, born in
April and July. Females are polyestrus, in estrus for only one day, with a gestation period of 41 days.
Weaned (and can glide) at eight weeks. Mother and young will stay
together until next litter. Will
breed in one year (although many studies show summer births often bear young
the following spring). Young females usually have one litter, while older
females often have two litters. Life
span of three to five years, with records of up to 13 years in captivity.
Dens/Nest: Dependent on cavities in
trees, often made by woodpeckers (15 - 20 feet above the ground). Has a primary nest
and several secondary nests used intermittently as feeding stations and, even
some for defecating stations, with openings of 1 ½ to 2 inches. Are known to
make summer leaf nests, but being smaller than the northern flying squirrel,
it can more often find a suitable tree cavity. Nests are lined with lichens or finely chewed bark.
Outside nests are 8" - 10" in diameter.
Known to reuse fox or gray squirrel nests, or even bird houses.
Tracks: The give away is the "sitzmark",
or landing spot, with the pattern of feet leaving the site, much like a gray
squirrel, only smaller (rear foot 1 5/8" in length, with a straddle of
3 3/4 inches).
Scat: Indistinct piles, each
dropping less than 1/4" in length.
Remarks:
A very small tree squirrel with loose skin between the limbs. Belly hairs
totally white, which differentiate the southern from the northern flying
squirrel (whose white belly hairs have a gray base). Extremely arboreal, can glide up to 260 feet (normally at a 30
degree slope), although 30 to 50 feet is more common, and capable of turning
90 degrees in mid-flight. Nut-caching fall habits are photoperiodically
triggered (short days). Those from SC and western NC are darker than those
from MD, VA, and eastern NC. Shy and docile, they make good pets, except they
can be quite noisy at night.
Audubon and Bachman reported
seeing at least 200 in and under several large beech and oak trees near
Philadelphia.
At
night, the eyes of the flying squirrel will shine red by the light of a
flashlight.
The
northern and southern flying squirrels are the only two species in the
genus.
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Family
Castoridae – Beaver
With
only two species worldwide, this is truly a small family. The other species, Castor
fiber, is native to portions of Europe and Asia. Numerous closely related family members existed in
prehistoric times, including the Pleistocene and late Tertiary. One was a 700 - 800 pound, muskrat-like animal that fed on
marshy vegetation. Another
extinct group constructed deep, spiraling burrows.
The
beaver, the only species in North America, is the largest rodent in North
America, weighing 88 pounds, or more.
Although
it is frequently reported that a beaver will continue growing throughout its
life, studies indicate that growth basically terminates at age four or
five.
AMERICAN
BEAVER (Castor
canadensis) (beaver; from Canada)
ARTICLES
Appalachian
Region Distribution:
Throughout, due to restocking. Was basically extirpated from eastern US by the
turn of the century.
Continental Range: All of North America. Only
one recognized eastern
US subspecies.
Abundance: Becoming more common.
Population Density: Depending on
habitat quality, studies show .2 to
2 colonies/square mile (up to 8/square mile in ideal habitat) (one colony equals 4-8 individuals), or one
colony per 0.4 - 1.5 miles of stream habitat, up to a maximum of 4.2 per
stream mile.
Size and Molt: Head and body 25 to
35 inches. The largest rodent in the Appalachian region, weighing 35 to 70 pounds, with a
record
as of 1981 of 115 pounds.
Second
largest rodent in the world, with only the capybara of South America being
larger. While many references state that beaver grow continuously throughout
their life, others say they reach their practical full size after 3 -5
years. Beaver are somewhat smaller in the southern part of their range.
It can be assumed beaver found in Appalachian streams and rivers will be on
the small size, based on food quality and quantity compared with coastal
marsh/ broad piedmont-coastal plain rivers. One molt.
Mammae: Two pair.
Habitat: Live along water courses
having adequate tree supply.
Active Period: Nocturnal and
crepuscular, year-round. Most active in the fall to repair the dam and create
a food cache.
Diet: Vegetarian, feeding on the
cambium layer of buds and twigs in winter, aquatic plants and grasses in
summer. A colony of 6 to 8 beaver will consume about 1,000 trees a year.
Known to "mow down" an entire aspen forest before other
trees are eaten. Coprophagy is
known to occur among beaver. Beaver
are unable to digest cellulose any better than any other non-ruminant mammal,
thus, large quantities of woody fibrous material must be eaten. Will cache branches in fall underwater (cache can be ten feet
high and forty feet wide) for winter food, which, in the north, must last for
up to six months. Caches are not cut until after the sap has returned to
the roots, minimizing chance of spoilage. In the south, such caches are not made.
In addition, brown fat, stored in the tail, is utilized to provide
needed winter energy. One study
found witch hazels were cached for food, while maple was eaten on the spot.
Beaver will discriminate among aspen trees, “testing” the bark on
aspens, and selecting those individuals with a lower concentration of natural
toxic plant compounds in the bark.
Home Range: Within 660 feet from the lodge.
Social Structure: Monogamous,
gregarious and
very territorial (as a colony). The social
structure of a beaver colony is based on the mating pair. Living together in a lodge, beaver live in social units of
about 6, consisting of a mating pair, the yearlings, and the kits (and
occasionally one or more that are about 2.5 years old).
Larger colonies (up to 12 members) are found in higher quality habitat.
Most sources say beaver mate for life (monogamous).
PA mammals says the female is reported to mate for life, although males
are polygynous. There usually is only a
single breeding female in a colony. The female appears to be dominant
over both males and young most of the time. Bonds normally
last only a few years, with the death of one of the mates.
At this time, a member of a younger generation from another colony
replaces the adult. This
difference in age in the couples is common. It is normally the female that
selects the home site. If the
paired male dies, the female remains at the existing site.
If the female dies, the territory may be abandoned.
The two-year olds are driven off (or instinctively disperse) a few
miles to establish their own range (one to five miles upstream or downstream), at which time they have reached sexual
maturity. Castor scent mounds are made to stake a claim, which may lead to
territorial fights, or the finding of a unmated beaver of the opposite sex.
