Eastern Grey Squirrel
Scientific & Common Name(s)
The Eastern grey squirrel is scientifically known as Sciurus carolinesis (Lawniczak, 2002). It is commonly referred to as the grey (or gray) squirrel, the bannertail squirrel, or the silvertail squirrel (Lawniczak, 2002).
Habitat & Geographic Range
The Eastern grey squirrel resides in the urban settings of eastern North America, ranging from the eastern regions of the United states to southeastern Canada (Koprowski, 1994). However, their populations are not restricted to within these ranges. Eastern grey squirrels were introduced into non-native populations in Europe, Ireland, Britain and England, where their populations thrived in each environment (Bertolino et al., 2013). Bertolino et al. (2013) found that when the non-native Eastern Grey Squirrel was introduced into Italy, the species managed to take over the red squirrel population by increasing their occupancy range to 2016km2. Though they seem to be a versatile species, grey squirrels prefer habitats with mature hardwood forests, where they reside in tree cavities or leafy nests (Saunders, 1988). Additionally, Tounzen et al. (2013) found that the grey squirrels inhabit riparian and upland forest, which include nearby fresh water sources and minimal open land, providing security for the grey squirrels. Furthermore, the team found that the home range of females is typically less than males, especially if the female is a lactating female. Finally, Saunders (1988) mentions that the most commonly observed suburban and urban areas which grey squirrels inhabit include towns, cities, and parks.
Size/Weight & Lifespan
The grey squirrel ranges in total size from 380mm to 525mm, with the length of its tail making up 150mm to 250mm of this total (Koprowski, 1994). Furthermore, Koprowski (1994) found that an adult grey squirrels body mass ranges from 300g to 710g. Infant grey squirrels on the other hand, are evidently smaller than adult grey squirrels, with their average weights recorded between 14-15g (Saunders, 1988). Saunders (1988) records that adult grey squirrels can live up to a maximum of 12 years in the wild or 20 years in captivity, with the mean life span of adult grey squirrels being 6 years. Comparatively, the life expectancy for infant grey squirrels is 1-2 years (Saunders, 1988).
Diet
The eastern grey squirrel diet consists primarily of fruits, nuts and samaras of deciduous trees (Moller, 1983). Though the species prefer seeds, they will resort to plant foods when seeds are limited, which may be during seasonal changes (Moller 1983). D.C. Thompson and P.S. Thompson (1980) refer to the species as “diurnal feeders”, meaning that they feed during the day. D.C. Thompson and P.S. Thompson (1980) found that Eastern Grey Squirrels primarily eat flowers and buds from deciduous trees in the spring time while husked nuts such as hickory and oak are commonly eaten in the winter. In the winter, the species have a stable diet, consisting of Sycamore maple, which are collected from the fall season (D.C. Thompson & P.S. Thompson, 1980). The spring diet is extremely diverse, consisting of 17 types of food, with the primary food items being from foods collected and stored during the winter months (D.C. Thompson & P.S. Thompson, 1980). D.C. Thompson and P.S. Thompson (1980) mention that the fall foods are eaten in order of maturing crop, usually beginning with hickory nuts. Though it is evident that grey squirrels are omnivorous mammals, they will consume animals or insects in times of extreme food shortages (D.C. Thompson & P.S. Thompson, 1980). Animal foods include eggs, small birds, and smaller rodents (Lawniczak, 2002).
Reproduction & Communication
Winter mating season occurs from January to February, while the summer mating season occurs from May to June (Thompson, 1977). During mating season, males follow a scent that the estrous female gives off, and communicate their interest in the female by constantly flipping their tails (Thompson, 1977). The squirrels’ sense of smell not only increases male reproductive success by aiding in identification of estrous females, but it also tells them information about the levels of stress of individuals around it (Lawniczak, 2002). Stress or the presence of danger is also communicated by squirrels through alarm calls, which sound like rapid clicking sounds (Lawniczak, 2002). Though the squirrels evidently demonstrate cooperation, they can also demonstrate competition for females. Male squirrels compete amongst themselves via distinct vocalizations (Thompson, 1977). This vocalization also communicates to other males that there is competition between males for a female, so other males run to the area of the vocalization, to win over the female squirrel (Lawniczak, 2002). Most often, the dominant male copulates with the estrous female (Thompson, 1977). If the female is impregnated, the gestation period lasts 40-44 days, after which the female bears 1-9 infants, depending on her age (Saunders, 1988). Most females begin reproductive life at 1.25 years, and bear young twice a year (Lawniczak, 2002). Saunders (1988) notes that younger mothers tend to have fewer offspring.
Predation: Does the animal have any predators?
Eastern grey squirrels are preyed on by red foxes, bobcats, grey wolves, coyotes, lynx, humans and raccoons (Lawniczak, 2002). Though they have predators, their speed and vigilance makes them difficult to capture (Lawniczak, 2002).
Conservation Status
The eastern squirrel population is said to be of least concern with regards to conservation status (Bertolino et al., 2013). The reason for this is because the species thrives when introduced to non-native habitats, illustrating that the species is tolerant to changing environments.
Did You Know?
Just as snakes can wipe out a nest of baby squirrels, squirrels can eat infant snakes in times of food shortages. So, who is the real predator?
References
Bertolino, S., di Montezemolo, N.C., Preatoni, D.G. et al. (2014). A grey future for Europe: Sciurus carolinensis is replacing native red squirrels in Italy. Biological Invasions, 16: 53, doi:10.1007/s10530-013-0502-3
Thompson, D.C. (1977). Reproductive behavior of the grey squirrel. Canadian Journal of Zoology, 55:7, 1176-1184. Doi: 10.1139/z77-152
Thompson, D.C., & Thompson, P.S. (1980). Food habits and caching behavior of urban grey squirrels. Canadian Journal of Zoology, 58:5, 701-710. Doi: 10.1139/z80-101
Moller, H. (1983). Foods and foraging behaviour of Red (Sciurus vulgaris) and Grey (Sciurus carolinensis) squirrels. Mammal Review, 13:2-4, 81-98. Doi: 10.1111/j.1365-2907.1983.tb00270.x
Saunders, D.A. (1988). Gray Squirrel (Sciurus carolinensis Ord). Retrieived October 20, 2016, from http://www.esf.edu/aec/adks/mammals/gray_squirrel.htm
Koprowski, J. (1994). Sciurus carolinensis. Mammalian Species, 1-9. Doi: i0076-3519-480-01-0001
Tounzen, M.R., Epperson, D., & Taulman, J.F. (2013). Home Range and Habitat Selection of Eastern Gray Squirrels (Sciurus carolinensis) in a Small Urban Hardwood Forest. Transactions of the Kansas Academy of Science, 115:3-4, 89-101. Doi: 10.1660/062.115.0301
Lawniczak, M. (2002). Sciurus carolinensis. Animal Diversity. Retrieived October 20, 2016, from http://animaldiversity.org/accounts/Sciurus_carolinensis/
