Observations by anniienguyen

Scientific & Common Names
Scientifically, the Eastern Gray Squirrel is known as Sciurus carolinensis. Other common names this particular species of squirrel goes by are Gray/Grey Squirrel, Bannertail, and Silvertail (Canadian Wildlife Federation, 2016).

Habitat & Geographic Range
The gray squirrel is also known for being a successful invasive species, and can thrive in various habitats and geographic ranges once introduced. The species is more prevalent in mature continuous forests, with higher density populations in areas with trees that provide winter-storable foods such as oaks, walnuts, and hickory (Bertolino, 2008; Lawniczak, 2002). These silvertail squirrels spend most of their time in the tree tops, commonly descending to feed, forage, and store food for the winter (Hamilton, 1990). The gray squirrel is the largest tree squirrel native to eastern North America, and can be found dispersed from the Gulf of Mexico to southern Quebec and Ontario (Bertolino, 2008). They’ve been known to invade many parts of Europe - such as Italy and England from the U.S., and Scotland from Canada (Koprowski, 1994). Gray squirrels were introduced to Britain in the late 19th century and thus far have replaced the native red squirrel (S. vulgaris) in most mainland wooded areas in southern Britain (Kenward et al, 1998). This is just one example of their prowess as an invasive species.

Size/Weight & Lifespan
The S. carolinensis species of squirrel are a medium-sized tree squirrel with no sexual dimorphism in size or colouration, resulting in both sexes looking relatively similar (Koprowski, 1994). The typical gray squirrel can range from 380-525mm in body length, and 300-710g in weight (Bertolino, 2008). The average weight of a gray squirrel is 540.33g (Lawniczak, 2002). The average expected lifespan is less than six years, however some wild gray squirrels have been observed to live up to 13 years (Hamilton, 1990).

Diet
Evidently, the gray squirrel’s ability to invade a variety of different habitats and geographic ranges has proven to be pronounced. Its invasive success can be attributed to its versatility in diet, which varies with habitat and season. In the spring, their diet consists of buds of hardwood trees, shoots, and flowers (Moller, 1983). Their diet shifts to include more coarse plant and animal foods, the winged seeds of trees (samaras), seeds, berries and other wild fruits, nuts, and apples in the summer (Moller, 1983; Canadian Wildlife Federation, 2016). During the autumn, hard nuts such as acorns, hickory nuts, butternuts, walnuts, and pine seeds are plentiful for consuming (Canadian Wildlife Federation, 2016). During this time, squirrels also engage in hoarding an abundance of food to prepare for the winter; burying hundreds of nuts and seeds for survival throughout the winter (Canadian Wildlife Federation, 2016). It is not unusual for squirrels to rely on bird feeders as a source of food, especially in winter months (Hamilton, 1990). Gray squirrels have also been known to feed on fungi, some insects, and an occasional nest of birds’ eggs or young birds (Bertolino, 2008; Hamilton, 1990). Individuals consume 400-900g of food per week (Hamilton, 1990).

Reproduction & Communication
The eastern gray squirrel undergoes two reproductive seasons per year in the winter (January-February) and summer (June-July) (Hamilton, 1990). However, only female squirrels over the age of two will breed in both of these reproductive seasons (Canadian Wildlife Federation). Most females are able to begin reproducing at 1.25 years, whereas young males are sexually mature by 11 months (Lawniczak, 2002). When a female is in estrus, or in “heat”, she is sexually receptive and fertile; exhibiting this by displaying an enlarged pink vulva, which typically lasts less than 8 hours (Lawniczak, 2002). A receptive female gray squirrel exhibits courtship behaviour days prior to estrus by continuously calling out from the trees with a distinctive duck-like vocalization (Hamilton, 1990). This can lead to male squirrels following a certain female’s calls 5 days before estrus, and as many as 34 males have been known to be attracted to an estrous female from distances as far as 500m (Koprowski, 1994). As the males gather, fighting may arise to determine a social hierarchy among the males (Hamilton, 1990). Pardo et al (2014) conducted a study in which they concluded that S. carolinensis communicate via certain configurations and tightness in the curve of the tail. Dominant males use subordinate males’ tail configurations to decide how aggressively to act in order to beat out their male competitors (Pardo et al, 2014). The dominant male will usually be the one allowed to mount the female dorsally and engage in copulation, which lasts less than 30 seconds (Koprowski, 1994). If copulation proves successful, the gestation period will begin and ranges from 40-44 days (Canadian Wildlife Federation, 2016). Litter sizes average three young, but range from one to six depending on the reproductive season with summer litters generally being larger relatively (Hamilton, 1990).

Predation: Does the animal have any predators?
The predators of these medium-sized mammals include other mammals such as minks, weasels, red foxes, lynx, coyotes, and wolves (Lawniczak, 2002). Young squirrels in the nest are preyed on by raccoons, snakes, and red squirrels (Hamilton, 1990). The gray squirrel also has many bird predators, such as the Northern Goshawks, Red-tailed Hawks, and Great Horned Owls (Hamilton, 1990). Luckily, the gray squirrel is extremely agile in the trees making it difficult for their predators to apprehend them when in pursuit (Lawniczak, 2002).

Conservation Status
According to the IUCN Red List of Threatened Species, the gray squirrel is listed as being of Least Concern (Cassola, 2016). There are no major threats to this specific species, and its current population trend is that it is increasing (Cassola, 2016).

Did You Know?
Squirrels bury hundreds of seeds and nuts for food storage for the upcoming scarce winter season, and hope to find them again using their highly developed sense of smell. However, some of these seeds and nuts will never be found again by their owners. Instead, they will germinate and grow into new trees; demonstrating that the eastern gray squirrels are nature’s little tree huggers. So the next time you see a tree, instead of wondering WHO planted it.. wonder WHAT did! (Hamilton, 1990).

References
Bertolino, S. (2008). Introduction of the American grey squirrel (Sciurus carolinensis) in Europe: a case study in biological invasion. Current Science, 95(7). Retrieved from https://www.researchgate.net/publication/242084905_Introduction_of_the_American_grey_squirrel_Sciurus_carolinensis_in_Europe_A_case_study_in_biological_invasion.
Canadian Wildlife Federation: Eastern Grey Squirrel. (n.d.). Retrieved from http://cwf-fcf.org/en/resources/encyclopedias/fauna/mammals/eastern-grey-squirrel.html
Cassola, F. (2016). Sciurus carolinensis. The IUCN Red List of Threatened Species 2016: e.T42462A22245728. Retrieved October 25 2016, from http://www.iucnredlist.org/details/42462/0.
Hamilton, H. (1990). Hinterland Who's Who - Eastern Grey Squirrel. Retrieved October 25, 2016, from http://www.hww.ca/en/wildlife/mammals/eastern-grey-squirrel.html#sid2
Kenward, R. E., Hodder, K. H., Rose, R. J., Walls, C. A., Parish, T., Holm, J. L., . . . Doyle, F. I. (1998). Comparative demography of red squirrels (sciurus vulgaris) and grey squirrels (sciurus carolinensis) in deciduous and conifer woodland. Journal of Zoology, 244(1), 7-21. doi:10.1111/j.1469-7998.1998.tb00002.x
Koprowski, J. (1994). Sciurus carolinensis. Mammalian Species, (480), 1-9. doi:1. Retrieved from http://www.jstor.org/stable/3504224 doi:1
Lawniczak, M.K. (2002). Sciurus carolinensis. Animal Diversity Web. Retrieved October 25, 2016 from http://animaldiversity.org/accounts/Sciurus_carolinensis/
Moller, H. (1983). Foods and foraging behaviour of Red (Sciurus vulgaris) and Grey (Sciurus carolinensis) squirrels. Mammal Review, 13: 81–98. doi:10.1111/j.1365-2907.1983.tb00270.x
Pardo, M. A., Pardo, S. A., Shields, W. M., Pardo, M. A., Pardo, S. A., Shields, W. M., . . . Shields, W. M. (2014). Eastern gray squirrels (sciurus carolinensis) communicate with the positions of their tails in an agonistic context. The American Midland Naturalist, 172(2), 359-365. doi:10.1674/0003-0031-172.2.359