Sciurus carolinensis (Grey Squirrel)
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Sciurognathi > Family: Sciuridae (squirrels)
Sciurus carolinensis, Company Gardens, Cape
Town, South Africa. [photo
Robertson, Iziko ©]
Indigenous to North America and introduced by Cecil John
Rhodes to Cape Town around the turn of the 19th-20th Century. Grey squirrels are
common in the Western Cape wherever there are pines and oaks and has not spread
significantly into natural vegetation. Hence, while alien to South Africa, it is
not considered a serious threat to local biodiversity although it does
supplement its vegetarian diet by predation of eggs and chicks in bird's nests.
Squirrels are easily recognized with their cylindrical
bodies and bushy tails. They show a marked difference in coat colour in winter
and summer. The summer coat is generally a brownish-grey, while the winter coat
is a silver-grey. The underparts are white or just off-white. Their bushy tails
have several uses; they serve for balance while running, as a rudder when
jumping, as a signal flag when communicating and as a blanket that they wrap
around for warmth when sleeping. The eyes are large surrounded by a light white
or off-white coloured ring. Placed on the sides of the head they give the
squirrel a wide field of vision. There are touch sensitive whiskers (vibrissae)
on the head, feet, and the outsides of the legs. Squirrels are extremely agile
when moving through the trees and have prehensile limbs and long sharp claws for
gripping. Their incisors grow continuously and are worn back down with use.
Although not common white albinos and melanistic black forms also occur in some
Total Length 50 cm; weight 600g '
I C P M =
Distribution and habitat
Native to the hardwood forests of North America, the Grey
squirrel was introduced into South Africa by Cecil John Rhodes. At the turn of
the 19th century he released squirrels on Groote Schuur estate in Cape Town. By
the 1970’s their range had extended as far as Swellendam in the Western Cape.
Their distribution is patchy and discontinuous being closely associated with oak
trees and pine plantations, and expands and contracts with the establishment and
removal of the trees. They are also found in vineyards and deciduous fruit
orchards where pine trees have been planted as windbreaks. Readily available
water is also an important requirement. Grey squirrels are unable to utilize
fynbos vegetation, and this serves to buffer its spread. Most of the indigenous
trees do not bear fruit or berries suitable for their food requirements. To date
their range remains confined to the south-western Cape and in most cases the
squirrels will only expand their range by introduction new
plantations.Restricted to pine and oak plantations, as well as suburban gardens
in the south-western Cape. Natural distribution is North America.
Grey squirrels are solitary, except when a female is
accompanied by her young. They are diurnal and may be seen at anytime of the day
but are generally most active in the early morning and later in the afternoon.
Although it is an arboreal (tree dwelling) species, squirrels spend a lot of
time foraging on the ground. They rest in dreys, a spherical nest, constructed
in the branches of the trees. These nests are normally about the size of a
soccer ball and made up of twigs, shredded bark, leaves and any other soft
materials such as string, paper and rags. It is thickly lined with dry grass,
moss and fur and is very well insulated. Squirrels will also make use of tree
holes that they line with leaves and other soft litter. Tree squirrels do not
hibernate, however, in cold weather they will stay in their nests only leaving
every few days when it is necessary to find food.
When threatened the individual will flatten its body on the
side of the tree trunk away from the threat and remain completely still until it
is safe to move again. The alarm call is a rapid scolding “kuk-kuk-kuk”.
Squirrels are primarily vegetarian, with acorns and pine
seeds making up most of their diet. When unavailable they will eat other nuts
and seeds as well as fruit, young shoots and buds, and flowers. They will also
eat insects, fungi, bird’s eggs, nestlings and small vertebrates if they are
available. Grey squirrels hoard acorns, pine nuts and other seeds by burying
them safely in the soil. Squirrels will poach nuts from another’s larder, this
leads to squirrels bury hundreds of nuts in a season and scattering their
stores. Many seeds are never retrieved and results in inadvertent tree-seed
dispersal and squirrels acting as inadvertent reforesters. This long
co-evolution of tree-squirrels with many of the forest tree species, has
resulted in these trees producing such abundant crops of nuts that many buried
nuts are never recovered and are left to germinate.
The gestation period is about 45 days. The young are born
in the Western Cape during two main periods spring (August/November) and summer
(December/February). The average litter size of the gray squirrel is 3. The
young are born naked and blind and only open their eyes at about 4 weeks old.
Fur begins to appear after about 2 weeks and the young will remain in the nest
until they are 5 – 6 weeks old. Weaning starts at about 7 weeks and is completed
by the time the young are 10 weeks old. The adult size is reached at about 9
months. Females may have 2 litters annually.
Other than its introduction to the Cape Peninsula, the Grey
squirrel has also been introduced in the UK and Europe. In the UK and Northern
Italy the indigenous Red squirrel is listed as near threatened due to exclusion
by the Grey squirrel. While it is regarded as an invasive alien in South Africa,
the Grey squirrel is currently not problematic as its distribution is limited to
commercial plantations and urban gardens. The Grey squirrels along the Oak-lined
Government Avenue in Cape Town are a major tourist attraction and hardly a
minute goes by in the day without someone photographing one of them.