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Eastern gray squirrel
Sciurus carolinensis is a medium sized tree squirrel with no sexual
dimorphism in size or coloration. The dorsal surface ranges from
grizzled dark to pale grey and may have cinnamon tones. The ears are
pale grey to white and its tail is white to pale grey. under parts
are grey to buff. Melanism is common in the northern portions of the
range and albinism is rare in all areas. There are a total of 22
teeth in the adults with a dental formula of i (1/1), c (0/0), p
(2/1/), m (3/3). The total length of these squirrels ranges from 380
to 525 mm, tail length ranges from 150 to 250 mm, ear length ranges
from 25 to 33mm, and hind foot length ranges from 54 to 76mm.
Reproduction
Males compete among themselves for the ability to mate with female
eastern grey squirrels. Females may mate with more than one male as
well.
Males start following females 5 days before estrus and may come from
as far away as 500 meters. Estrus in the female is indicated by an
enlarged pink vulva, a condition which usually lasts less than 8
hours. The vagina is closed in prepubescent and anestrous females.
Copulation lasts less than thirty seconds. After ejaculation, a
gelatinous white vaginal plug forms, preventing further sperm entry.
Breeding occurs in December-February and May-June and is slightly
delayed in more northern latitudes. Gestation lasts 44 days. Most
females begin their reproductive life at 1.25 years but can bear
young as early as 5.5 months. Females may bear young twice a year
for more than 8 years. Males usually are sexually mature by 11
months but maturity can be delayed by as much as two years if the
young males are housed with a dominant adult male. Inactive testes
weigh 1g, whereas active testes weight 6-7g. This cycle of
testicular recrudescence and regression occurs twice a year.
Newborns are naked with the exception of their vibrissae and they
weigh from 13-18g. Young are altricial. Weaning begins in the
seventh week and is completed by the tenth. At this point, the
juvenile pelage is lost. Adult size and mass are reached at 9
months. Two litters are born each year in late winter and midsummer
with generally 2-4 young per litter (up to 8 young are possible).
Newborns are naked with the exception of their vibrissae. Vibrissae
are small hairs around the nose and mouth that are used for touch,
much like the whiskers of a cat. The newborns weigh from 13-18g.
Young are altricial. They are cared for in the nest by their mother
until they reach independence. Weaning begins in the seventh week
and is completed by the tenth. At this point, the juvenile hair is
lost. Adult size and mass are reached at 9 months old.
The maximum longevity is 12.5 years in the wild but a captive female
lived to be over 20 years of age.
Behavior
During the spring, summer and autumn, squirrels have their peak
activity times about 2 hours after sunrise and 2-5 hours before
sunset. This allows them to avoid the heat of the day. During the
winter, they are unimodally diurnal with a peak just 2-4 hours
before sunset. Generally, females are more active in the summer
months and males are more active in the winter months. A dominance
hierarchy forms in males during breeding times; females mate with
several males. Related individuals may defend a territory (Taylor
1969). Squirrels occupy two types of homes, including a permanent
tree den as well as a nest of leaves and twigs on a tree crotch
30-45 feet above the ground. Females nest alone when pregnant, and
lactating females are especially aggressive and avoided by others.
Home ranges are generally larger in the summer. Home range sizes are
negatively correlated with squirrel density. Lactating females may
decrease their home ranges by as much as 50%. Home ranges are used
in the same sequence each day.
Food Habits
Sciurus carolinensis feeds mostly on nuts, flowers and buds of more
than 24 species of oaks, 10 species of hickory, pecan, walnut and
beech tree species. Maple, mulberry, hackberry, elm, bucky and horse
chestnut fruits, seeds, bulbs or flowers are also eaten along with
wild cherry, dogwood, hawthorn, black gum, hazelnut, hop hornbeam
and gingko tree fruits, seeds, bulbs and/or flowers. The seeds and
catkins of gymnosperms such as cedar, hemlock, pine, and spruce are
another food source along with a variety of herbaceous plants and
fungi. Crops, such as corn and wheat, are eaten, especially in the
winter. Insects are eaten in the summer and are probably especially
important for juveniles. Cannibalism has been reported, and
squirrels may also eat bones, bird eggs and nestlings, and frogs.
They bury food in winter caches using a method called scatter
hoarding and locate these caches using both memory and smell. In
captivity they should be offered a complete diet of rodent lab blocks, and rat or mouse
mix, with bits of fruit or veggies regularly. Cheerios or wheat
bread are great treats, in small quantities. Do NOT feed chocolate,
fried foods, salted foods, candy or junk food! They may enjoy
crickets and mealworms if they are captive bred, never feed wild
insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium
during nursing and growth due to demands on their systems at those
times, but take care not to overdo it. Water bottles should be used
to proved constant, clean water. Ceramic or stoneware food dishes
work well for keeping seeds or fresh foods off the floor, and a wire
mesh hopper that allows them to eat the lab blocks through without
extra waste.
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