Eastern Gray Squirrel
Sciurus carolinensis ranges over the eastern United States to just west of the Mississippi River and north to Canada. Introductions have occurred in the western states and some of Canada that was not previously inhabited, as well as in Italy, Scotland, England and Ireland. Sciurus carolinensis prefers habitats of mature continuous woodlands of greater than 40 hectares with diverse under story vegetation. Densities are highest in forests with trees that produce foods that last through winter storage such as oaks (Quercus) and walnuts (Juglans).
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.
