Observations by kaseym

Scientific Name:
Sciurus carolinensis
Common Name:
Eastern grey squirrel
Habitat & Geographic Range:
Eastern grey squirrels are native to North America, specifically southeastern Canada and the eastern and mid-western United States (Lioy, Mori, Wauters, & Bertolino, 2016). This species of tree squirrel commonly lives in highly wooded areas, although some may be found in cities. In general, their populations are the densest in areas that include nut-producing trees, such as oaks, since nuts are easily stored for the winter (Koprowski, 1994).
In the 1800s, grey squirrels were brought to Europe from North America, specifically to Britain, Ireland, and Italy (Lioy et al, 2016). The species was later introduced to both South Africa and Australia via Britain. However, the eastern grey squirrel became locally extinct in Australia by 1973 (Koprowski, 1994). These squirrels are considered an invasive species in Britain because they threaten native red squirrels, Sciurus vulgaris, through competition for resources. They are also a threat to regional plant life, as they are known to strip bark from trees in the UK (Nichols, Drewe, Gill, Goode, & Gregory, 2016).
Size & Lifespan:
The eastern grey squirrel is generally medium-sized relative to other species. Adults weigh between 400 and 720 grams and grow to be approximately 42 to 55 centimeters in length including their tails (Lioy et al., 2016). The life expectancy of a newborn grey squirrel is only one or two years. However, if they reach adulthood, their life expectancy increases to approximately six years. Eastern grey squirrels are known to live much longer, on average, in captivity than in the wild due to the absence of predators and fluctuations in food availability (Koprowski, 1994).
Diet:
The diet of the eastern grey squirrel consists mostly of nuts, fruits, and seeds. They commonly consume both acorns and hazelnuts. These squirrels often eat fungi and berries to supplement their diet, while other items such as bird eggs, small invertebrates, tree bark, and lichen act as secondary food sources. Overall, their food consumption varies by season due to changes in availability, especially in the spring and summer when nuts from the previous autumn are more scarce. For example, lactating females have been known to gnaw on the bones and antlers of other animals as a source of calcium (Nichols et al., 2016). There is a peak in activity among these squirrels at feeding sites around midday and dominant squirrels tend to monopolize food sources by keeping smaller competitors away. Eastern grey squirrels compete for the same food sources with other small animals, such as corvids (Jayne, Lea, & Leaver, 2015).
Reproduction & Communication:
Little or no sexual dimorphism exists between male and female grey squirrels in terms of size and colour. Most females are not able reproduce until they are over a year old, while males reach sexual maturity at around 10 to 11 months old. Females tend to mate with several males and can reproduce for more than eight years after reaching sexual maturity. A hierarchy exists among males, with some viewed as more dominant than others (Koprowski, 1994). There are two annual breeding seasons in winter and summer, and population sizes fluctuate each year according to food availability and the cold temperatures in winter months (Nichols et al., 2016). Each litter consists of two or three young on average, but litter size decreases when food is scarce. Newborns do not have an fur and weigh between 13 and 18 grams (Koprowski, 1994).
Grey squirrels use several different vocalizations to communicate, which differ according to their purpose and context. While foraging, they may use alarm sounds and body language to warn others of predators. Squirrels also use cooing noises for communication between males and females during breeding, as well as between mothers and their young to show affection. The species has a number of other communication methods that involve both gestures, such as tail movements, and facial expressions (Koprowski, 1994).
Predation:
Some of the main predators of the eastern grey squirrel include larger rodents, large birds such as hawks and owls, snakes, foxes, and domestic animals such as dogs (Jayne, Lea, & Leaver, 2015). Grey squirrels make up approximately five percent of the diet of timber rattlesnakes, which reside in the same region of North America (Pomento, Perry, Denton, Gibbs, & Holding, 2016). The risk associated with predators weighs heavily on decisions about foraging location and time span. Squirrels often participate in social foraging to reduce their vulnerability to predators. Although some individuals will choose areas that are more exposed to predators in order to avoid competition for resources, foraging in the company of others increases safety and is often seen as beneficial. Alarm behaviours include standing on the hind legs, waving of the tail, and barking (Jayne et al., 2015).
Conservation Status:
The eastern grey squirrel is listed as “Least Concern”, the lowest level of conservation. Grey squirrels are not currently threatened by extinction. On the contrary, populations are thought to be growing in number (Lioy et al., 2016).
Did You Know?
Eastern grey squirrels may be able to evolve a resistance to the venom of the western diamond rattlesnake, C. atrox, which is present in the southwestern regions of the squirrel’s native geographic range. Serum-based inhibitors resist hemorrhagic activity in the blood of the grey squirrel after they are exposed to the bite of a rattlesnake. This serves as a useful defense mechanism, as rattlesnakes are one of the main predators of the grey squirrel (Pomento et al., 2016).
 
References

Jayne, K., Lea, S. E. G., Leaver, L. A. (2015). Behavioural responses of Eastern grey squirrels, Sciurus
coralinensis, to cues of risk while foraging. Behavioural Processes, 116, 53-61.
http://dx.doi.org/10.1016/j.beproc.2015.05.002

Koprowski, J. L. (1994). Sciurus carolinensis. Mammalian Species, 480, 1-9. Retrieved from
www.science.smith.edu/msi/pdf/i0076-3519-480-01-0001.pdf

Lioy, S., Mori, E., Wauters, L. A., Bertolino, S. (2016). Weight operated see-saw feeding hoppers are not
selective for red squirrels when greys are present. Mammalian Biology, 81, 365-371.
http://dx.doi.org/10.1016/j.mambio.2016.03.008

Nichols, C. P., Drewe, J. A., Gill, R., Goode, N., Gregory, N. (2016). A novel causal mechanism for grey
squirrel bark stripping: The calcium hypothesis. Forest Ecology and Management, 367, 12-20.
http://dx.doi.org/10.1016/j.foreco.2016.02.021

Pomento, A. M., Perry, B. W., Denton, R. D., Gibbs, H. L., Holding, M. L. (2016). No safety in the trees:
Local and species-level adaptation of an arboreal squirrel to the venom of sympatric
rattlesnakes. Toxicon, 118, 149-155. http://dx.doi.org/10.1016/j.toxicon.2016.05.003