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Scientific name: Tamiascurus hudsonicus
Common name: Red Squirrel
(Information in this Species Page was compiled by Moe Ortz in Biology 220W, Spring
2002, at Penn State New Kensington)
The red squirrel (Tamiascurus hudsonicus) is also called the chickaree
or the pine squirrel. The three common names for this animal describe its
general appearance, active vocalizing habits, and preferred habitat. The
scientific name, on the other hand, describes this species’ habit of making
extensive caches of buried food stuffs (“tamias”) and its predominantly high
latitude, North American distribution (“Hudson Bay”). Range and Habitat
The red squirrel is found throughout much of Canada and the northern United
States from the eastern seaboard to Alaska. Its range extends south, down
through the high altitude regions of the Rocky Mountains, well into northern New
Mexico. Their preferred ecosystems are cool, coniferous forests with dense,
interlocking canopies and abundant fungal resources. In the Rocky Mountains, red
squirrels are especially abundant in Norway spruce and red pine forests, while
in Pennsylvania and New York, they prefer mixed coniferous and deciduous forest
stands. They can also live in hedgerows, orchards, parks, and even buildings
(red squirrels once made a nest in my attic in fact….what a racket!). 
Appearance
An adult red squirrel is 10 to 15 inches long. It has a relatively thin tail
(thin for a squirrel, anyway) which makes up almost half of this overall length.
Males tend to be larger than females, but both genders have the same basic body
coat color patterns with red-brown dorsums (“backs”), white venters (“bellies”),
and often (especially in the summer) a lateral, black stripe separating the
brown and white regions. Their tails are predominantly the same red-brown color
of their backs outlined by broad, black bands and sometimes a white edging. The
body fur is replaced in two annual molts (one in the spring and another in the
fall). The hair on the tail, though, is only shed and replaced once a year.
Nests
Red squirrels make a variety of types of nests. Occasionally, they will dig
multi-chambered tunnels in loose soil under rotting logs, but most often they
will live up in the trees either among the branches or in a tree hole. Branch
nests are typically located sixty or more feet above the ground. They are
globular in shape (about a foot in diameter), and are constructed of interwoven
twigs, bark, leaves, grasses, feathers, fur, and almost any other available
materials. Tree holes, though, are the red squirrel’s preferred nesting
location. Natural tree cavities and abandoned woodpecker nests, especially in
coniferous trees, are highly favored. All nests are located with a maximum
diversity of escape routes and potential canopy pathways. Nests are used for
shelter and rest, for over-wintering (red squirrels do not hibernate), and as
brood chambers.
Locomotion and Activity Period
The red squirrel is an agile and daring arboreal (“tree dwelling”) species. It
runs along limbs that would seem to be far too insubstantial for its weight and
is capable of great leaps from branch to branch and from tree to tree. They run
through and up and down their trees with amazing speed and precision. Red
squirrels move about on the ground primarily in leaps that are 8 to 30 inches
long. Ground tracks of a red squirrel typically show the larger, five-toed hind
feet slightly ahead of the smaller, four-toed front feet reflecting the landing
and take-off body patterns involved in their leaping pattern of locomotion.
Their tracks are often clustered in distinct, square-sided, groupings.
The red squirrel is primarily a diurnally (“day-time”) active animal. It has
dual peak activity times in the morning and in the afternoon during the spring
and summer, a single peak in mid-day during the winter, and almost continuous
activity during the daylight hours of the fall. Nocturnal activities are
possible but are very limited. Inclement weather (heavy rain, snow, wind, etc)
may cause the red squirrel to remain in its nest for shelter for a day. Each
individual must, however, forage for food at least every other day.
Diet
Red squirrels are omnivorous, opportunistic feeders. They primarily eat the
seeds of a great variety of coniferous and deciduous trees. As one of its common
names indicates, pine cones are a particular favorite. Red squirrels are a major
cause of failure in pine reforestations since they eat anywhere from 60 to 100%
of a pine stand’s seed cones. Red squirrels will also eat many types of
invertebrates, fruits, fungi, bark, tree saps, and bird eggs. Their propensity
to strip tree bark to get at the tree’s rich phloem and cambium tissues is
another major source of forest damage and re-forestation failure wrought by
these animals. Red squirrels will also eat the young of birds, mice, rabbits,
gray squirrels, and snakes. They rarely drink water but instead get most of
their dietary moisture from fruits, berries, and fungi. Red squirrels actively
gather food stuffs during times of abundance and store great quantities of
materials in caches called “middens.” An individual squirrel may have up to six
of these middens near their nest. Each midden may contain up to a bushel of
dried seeds, cones, and mushrooms. The territorial nature of these squirrels is
directly related to the positioning of these middens.
Life Span and Reproduction
In captivity red squirrels can live for nine or ten years. In the wild, though,
their expected life spans are much shorter. Very few individuals live beyond
five years of age. Sixty percent of a newborn cohort dies in their first year,
another twenty percent of this cohort dies in their second year, and another ten
percent in the third. Less than ten percent of a birth cohort, then, is expected
to live into their fourth year of age. Females become sexually mature anywhere
from one to four years of age. They breed once a year in the southern portions
of their range but can breed twice a year in more northern habitats. Litter size
is typically between 3 and 5 but can be as large as 7. The young are weaned 65
days after birth but will remain close to their mothers throughout the summer
until early fall. Foraging behaviors, vocalizations, nest construction, and
mating and dominance behaviors are all learned by the young during this
post-weaning period.
Predation
Red squirrels are taken by a great variety of predators including almost all
type of hawks (including Cooper’s hawk, goshawks, red-tail hawks, red-shouldered
hawks, broad wing hawks, northern harriers, and sharp-shinned hawks), several
owls (including the great horned and the great gray), the bald eagle, the
American kestrel, red fox, lynx, pine martens, minks, and timber rattlesnakes.
Domesticated dogs are also a major source of mortality if not predation. Humans
also take large numbers of red squirrels each year primarily for their pelts
(red squirrels are, after muskrat and beaver, the third most abundantly
commercially harvested furbearing, wild animal in North America!).
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