Eastern Gray Squirrel

Taxobox
name = Eastern Gray Squirrel
status = LC
status_system = iucn3.1


image_width = 250px
domain = Eukarya
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Rodentia
familia = Sciuridae
genus = "Sciurus"
subgenus = "Sciurus"
species = "S. carolinensis"
binomial = "Sciurus carolinensis"
binomial_authority = Gmelin, 1788

The eastern gray squirrel ("Sciurus carolinensis") is a tree squirrel native to the eastern and midwestern United States and to the southerly portions of the eastern provinces of Canada. The specific epithet, "carolinensis", refers to the Carolinas, where the species was first recorded and where the animal is still extremely common. The native range of the eastern gray squirrel overlaps with that of the fox squirrel ("Sciurus niger"), with which it is sometimes confused, although the core of the fox squirrel's range is slightly more to the west.

A prolific and adaptable species, the gray squirrel has been introduced to, and thrives, in several regions of the western United States. It has also been introduced to Britain, where it has spread across the country and has largely displaced the native red squirrel, "Sciurus vulgaris". In Ireland, the red squirrel has been displaced in several eastern counties, though it still remains common in the south and west of the country. [Carey, M., Hamilton, G., Poole, A., and Lawton, C.. The Irish Squirrel Survey 2007. COFORD, Dublin – Report can be downloaded from www.coford.ie] There are concerns that such displacement might happen in Italy.

Description

As the name suggests, the eastern gray squirrel's fur is predominantly gray but it can have a reddish tinge. The eastern gray squirrel's belly is white and it has a large bushy tail. Particularly in urban situations where the risk of predation is reduced, both white- and black-colored squirrels are quite often found. The melanistic form, which is almost entirely black, is predominant in certain populations and in certain geographic areas, such as in large parts of southeastern Canada. There are also genetic variations within these, including gray squirrels with black tails and black colored gray squirrels with white tails.

Life cycle

Gray squirrels are mammals, and hence have live babies. They breed twice a year, the first litter being born in February or March, the second in August or September. There are normally three or four babies in each litter. [cite web |url=http://www.scambs.gov.uk/Environment/Pestsandnuisance/AnimalNuisanceandPests/squirrels.htm |title=Gray squirrels |accessdate=2008-07-10]

Gray squirrels have a gestation period of about 45 days. The young are weaned at 10 weeks old and leave the nest between April and June. The second litters arrive in June and July, leaving the nest during August and September. Gray squirrels do not hibernate. [cite web |url=http://www.macclesfield.gov.uk/pdfs/grey_squirrel.pdf |title=Grey squirrel Advisory |accessdate=2008-07-10]

Baby gray squirrels don't know by instinct what is good to eat, and hence will eat all sorts of random things, leaving them broken and half-eaten.

Gray squirrels can start breeding as early as 5.5 months, [cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_carolinensis.html |title=Sciurus carolinensiseastern gray squirrel |accessdate=2008-07-10] but usually breed for the first time at a year old. [cite web |url=http://www.northampton.gov.uk/site/scripts/documents_info.php?documentID=588&pageNumber=4|title=SquirrelsWhat is the life cycle of the grey squirrel? |accessdate=2008-07-10] The gray squirrel can live to be 20 years old in captivity, but usually in the wild only live to about 12 years old. [cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_carolinensis.html |title=Sciurus carolinensiseastern gray squirrel |accessdate=2008-07-10]

Behavior

Like many members of the family Sciuridae, the eastern gray squirrel is a scatter-hoarder; it hoards food in numerous small caches for later recovery. Some caches are quite temporary, especially those made near the site of a sudden abundance of food which can be retrieved within hours or days for re-burial in a more secure site. Others are more permanent and are not retrieved until months later. It has been estimated that each squirrel makes several thousand caches each season. The squirrels have very accurate spatial memory for the locations of these caches, and use distant and nearby landmarks to retrieve them. Smell is used once the squirrel is within a few centimeters of the cache.

Gray squirrels build a type of nest, known as a drey, in the forks of trees. The drey consists mainly of dry leaves and twigs. They may also build a nest in the attic or in the exterior walls of a house, often to the consternation of the homeowner. In addition, gray squirrels may inhabit a permanent tree den. [cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_carolinensis.html |title=Sciurus carolinensiseastern gray squirrel |accessdate=2008-07-10]

They will raid bird feeders for millet corn, and sunflower seeds but they are reported to dislike the slight capsaicin content of safflower seeds. So-called anti-squirrel birdseed preparations are available; the seeds are coated with chili pepper. The birds are unaffected because they cannot taste the capsaicin. Mixing hot pepper flakes into regular birdseed works well as a squirrel deterrent. Gray squirrels are notorious for digging bulbs from gardens. Their reputation for these habits has led some to call them "tree rats" or "fuzzy-tailed sewer rats". Eastern gray squirrels have a high tolerance for humans and inhabit residential neighborhoods and urban parks. Wild squirrels may even be enticed to accept food from people.

Gray squirrels are more active during the early and late hours of the day, and tend to avoid the heat in the middle of a summer day. [cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_carolinensis.html |title=Sciurus carolinensiseastern gray squirrel |accessdate=2008-07-10]

Predators include humans, hawks, mustelids, skunks, raccoons, domestic and feral cats, snakes, owls and dogs. On occasion, a squirrel may lose part of its tail while escaping a predator.

Communication

As in most other mammals, communication among gray squirrels involves both vocalizations and posturing. The eastern gray squirrel has a quite varied repertoire of vocalizations, including a squeak similar to that of a mouse, but more low pitched, a chatter, and a raspy "mehr mehr mehr". Other methods of communication include tail-flicking.

Diet

The eastern gray squirrel consumes a variety of foods such as inner tree bark, various seeds and acorns, walnuts, and other nuts.

Distribution

The eastern gray squirrel is common throughout most of its natural range and wherever it has been introduced. It readily becomes tolerant of humans and learns to take food left or offered by picnickers.

Introductions

The eastern gray has been introduced to a variety of locations on the west coast of North America, including the states of Washington and Oregon and, in California, to the city of San Francisco and the Peninsula area of San Mateo and Santa Clara counties, south of the city. It has become the most common squirrel in many urban and suburban habitats in the western United States north of central California. At the turn of the 20th century the eastern gray squirrel was introduced into South Africa, Ireland and England. It spread rapidly across England and then became established in both Wales and parts of southern Scotland. On mainland Britain, it has almost entirely displaced the populations of native red squirrels. On the island of Ireland, this displacement has not been as rapid, owing to the fact there was only a single introduction of gray squirrels in County Longford. Eastern gray squirrels have also been introduced to Italy, and the European Union has expressed concern that it will similarly displace the red squirrel from parts of the European continent.

Displacement of red squirrels

In the United Kingdom, the animal is known simply as the "grey squirrel" and it has few natural predators. This has aided their rapid population growth and has led to the species being classed as a pest. Measures are being devised to reduce their numbers, including one plan for famous television chefs to promote the idea of eating the squirrels. [cite news |url=http://news.bbc.co.uk/1/hi/uk_politics/4835690.stm |title=Jamie 'must back squirrel-eating' |publisher=BBC News |accessdate=2007-08-22] In areas where relict populations of red squirrels survive, such as the island of Anglesey, programmes seeking to eradicate pest squirrels are in progress in an effort to allow red squirrel populations to recover. [cite web |url=http://www.redsquirrels.info/ |title=Red squirrel conservation, squirrel ecology and grey squirrel management |publisher=The Friends of the Anglesey Red Squirrels |accessdate=2007-08-22]

Although complex and controversial, the main factor in the displacement of red squirrels by grays is thought to be the grays' greater fitness and, hence, a competitive advantage over red squirrels on all measures. [Wauters, L. A., Gurnell, J., Martinoli, A., & Tosi, G. (2002). Interspecific competition between native Eurasian red squirrels and alien grey squirrels: does resource partitioning occur? "Behavioral Ecology and Sociobiology, 52", 332-341.] Gray squirrels tend to be larger and stronger than reds and have been shown to have a greater ability to store fat for winter. These factors are thought to result in gray squirrels competing effectively for a larger share of the available food, resulting in relatively lower survival and breeding rates among red squirrels. Parapoxvirus may also be a strongly contributing factor; red squirrels are fatally affected by the disease, while grey squirrels are unaffected but thought to be carriers. Red squirrels are also less tolerant of habitat destruction and fragmentation than are the more adaptable grey squirrels, resulting in a decrease in the population of reds and a resultant expansion in the number of gray squirrels.

Similar factors appear to have been at play in the Pacific region of North America, where the native American red squirrels have been largely displaced by grays in parks and forests throughout much of the region.

Ironically, 2008 saw the rise of "fears" for the gray squirrel's future, as "black" (melanistic gray squirrels) begin to spread through the southern British population of gray squirrels. [cite web|url=http://www.bbc.co.uk/theoneshow/article/2008/05/eh_blacksquirrel.shtml|title=BBC's "The One Show" feature on Black Squirrels|accessdate=2008-05-15] Conversely, in the UK, if a grey squirrel is trapped, under the Wildlife and Countryside Act 1981 it is illegal to release a grey squirrel or to allow it to escape into the wild. They should be humanely destroyed. [cite web|url=http://www.defra.gov.uk/rds/publications/technical/tan_09.pdf|title=Defra Rural Development Service Technical Advice Note 09]

ee also

*Fox Squirrel
*Western Gray Squirrel

References

*IUCN2006|assessors=Baillie|year=1996|id=42462|title=Sciurus carolinensis|downloaded=6 May 2006
*ITIS|ID=180175|taxon=Sciurus carolinensis|year=2006|date=23 March

External links

* [http://www.arkive.org/species/ARK/mammals/Sciurus_carolinensis/ ARKive] Still photos, Videos.
* [http://www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/eastern_gray_squirrel.htm FCBS Directoy: Eastern Gray Squirrel]
* [http://belchonock.org.ua/ Squirrels are everywhere]
* [http://www.registrars.kent.edu/home/SITE_NAVS/history.htm A brief history of the black squirrel at Kent State University]
* [http://www.hww.ca/hww2.asp?id=89&cid=8 Eastern Gray Squirrel Facts from Hinterland Who's Who]
* [http://www.washingtonpost.com/wp-dyn/content/article/2005/05/18/AR2005051802251.html An Exotic Evolution: Black Squirrels Imported in Early 1900s Gain Foothold (from "The Washington Post")]
* [http://pages.cthome.net/rwinkler/graysquirrel.htm The Squirrel and the Computer] Reflections on the death of a suburban Eastern gray squirrel
* [http://www.wildlifeonline.me.uk/squirrels.html WildlifeOnline - Natural History of Tree Squirrels]
* [http://www.mnh.si.edu/mna/image_info.cfm?species_id=298 Smithsonian Eastern Gray Squirrel article]