Editing Eastern gray squirrel

{{short description|Tree squirrel native to eastern and central North America}}
{{Use dmy dates|date=September 2017}}
{{speciesbox
| name = Eastern gray squirrel<ref name="Thorington">{{MSW3 Sciuridae|id= 12400104|page= 760}}</ref>
| fossil_range = {{longitem|style=line-height:1.25em|{{nowrap|[[Rancholabrean|Late Pleistocene]] – present}} {{nowrap|(18,735–0 [[Before Present|YBP]])<ref name="Bentley1994"/>}}}}
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Cassola, F. |date=2016 |title=''Sciurus carolinensis'' |volume=2016 |page=e.T42462A22245728 |doi=10.2305/IUCN.UK.2016-2.RLTS.T42462A22245728.en |access-date=19 November 2021}}</ref>
| status2 = G5
| status2_system = TNC
| status2_ref = <ref name="NatureServe">{{cite web|title=Sciurus carolinensis|url=https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.104371/Sciurus_carolinensis|website=Natureserve Explorer|access-date=12 May 2024}}</ref>
| image = EasternGraySquirrel GAm.jpg
| image_caption = [[File:Grey Squirrel (Sciurus carolinensis) (W1CDR0001470 BD12).ogg|center|thumb|Calls recorded in Surrey, England]]
| genus = Sciurus
| parent = Sciurus (Sciurus)
| species = carolinensis
| authority = [[Johann Friedrich Gmelin|Gmelin]], 1788
| subdivision_ranks = Subspecies
| subdivision = * ''S. c. carolinensis''
* ''S. c. extimus''
* ''S. c. fuliginosus''
* ''S. c. hypophaeus''
* ''S. c. pennsylvanicus''
| synonyms = * ''Neosciurus carolinensis''<ref>{{Cite journal|doi = 10.1186/s12862-020-01639-y|title = Museomics of tree squirrels: A dense taxon sampling of mitogenomes reveals hidden diversity, phenotypic convergence, and the need of a taxonomic overhaul|year = 2020|last1 = De Abreu-Jr|first1 = Edson Fiedler|last2 = Pavan|first2 = Silvia E.|last3 = Tsuchiya|first3 = Mirian T. N.|last4 = Wilson|first4 = Don E.|last5 = Percequillo|first5 = Alexandre R.|last6 = Maldonado|first6 = Jesús E.|journal = BMC Evolutionary Biology|volume = 20|issue = 1|page = 77|pmid = 32590930|pmc = 7320592|s2cid = 220071854 | doi-access=free | bibcode=2020BMCEE..20...77D }}</ref>
* ''S. pennsylvanica''
* ''S. hiemalis''
* ''S. leucotis''
* ''S. fulginosus''
* ''S. migratorius''
| range_map = Sciurus carolinensis range map.svg
| range_map_caption = Native range in red
}}

The '''eastern gray squirrel''' ('''''Sciurus carolinensis'''''), also known, outside of the United States, as the '''grey squirrel''', is a [[tree squirrel]] in the genus ''[[Sciurus]]''. It is native to eastern North America, where it is the most prodigious and ecologically essential natural forest regenerator.<ref>{{cite journal |last1=Goheen |first1=Jacob R. |last2=Swihart |first2=Robert K. |year=2003 |title=Food-hoarding behavior of gray squirrels and North American red squirrels in the central hardwoods region: Implications for forest regeneration |journal=[[Canadian Journal of Zoology]] |volume=81 |issue=9 |pages=1636–1639 |doi=10.1139/z03-143}}</ref><ref>{{cite journal |vauthors=Steele MA, Hadj-Chikh LZ, Hazeltine J |year=1996 |title=Caching and Feeding Decisions by ''Sciurus carolinensis'': Responses to Weevil-Infested Acorns |journal=[[Journal of Mammalogy]] |volume=77 |issue=2 |pages=305–314 |doi=10.2307/1382802 |jstor=1382802 |doi-access=free}}</ref> Widely introduced to certain places around the world, [[Eastern grey squirrels in Europe|the eastern gray squirrel in Europe]], in particular, is regarded as an [[invasive species]].

In Europe, ''Sciurus carolinensis'' is included (since 2016) in the [[List of invasive alien species of Union concern|list of Invasive Alien Species of Union concern]] (the Union list).<ref>{{Cite EU regulation|serial=1143/2014|date=July 13, 2016|description=List of Invasive Alien Species of Union Concern|eurlextag=02016R1141-20220802}}</ref> This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.<ref>{{Cite EU regulation|serial=1143/2014|date=October 22, 2014|description=On the prevention and management of the introduction and spread of invasive alien species|eurlextag=32014R1143}}</ref>

==Distribution==
''Sciurus carolinensis'' is native to the [[Eastern United States|eastern]] and [[midwestern United States]], and to the southerly portions of the central provinces of [[Canada]]. In the mid-1800s the population in the midwestern United States was described as being "truly astonishing," but human predation and habitat destruction through deforestation resulted in drastic population reductions, to the point that the animal was almost absent from Illinois by 1900.<ref name=":1">{{Cite magazine |last=Evensen |first=Dave |date=Fall 2023 |title=The squirrel experiment |url=https://las.illinois.edu/system/files/inline-files/Magazine_Quadrangle_FALL23_web.pdf |department=LAS in History |magazine=The Quadrangle |publisher=[[University of Illinois Urbana-Champaign|University of Illinois]], College of Liberal Arts & Sciences |pages=26–27}}</ref>

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. The eastern gray squirrel is found from New Brunswick, through southwestern Quebec and throughout southern Ontario plus in southern Manitoba, south to [[East Texas]] and Florida.<ref name="iucn status 19 November 2021" /> Breeding eastern gray squirrels are found in Nova Scotia, but whether this population was introduced or came from natural range expansion is not known.<ref>{{cite journal |vauthors=Huynh HM, Williams GR, McAlpine DF, [[Richard W. Thorington Jr.|Thorington RW]] |date=December 1, 2010 |title=Establishment of the Eastern Gray Squirrel (''Sciurus carolinensis'') in Nova Scotia, Canada |journal=Northeastern Naturalist |publisher=Eagle Hill Institute |publication-place=United States |volume=17 |issue=4 |pages=673–677 |doi=10.1656/045.017.0414 |s2cid=84649999}}</ref>

A prolific and adaptable species, the eastern gray squirrel has also been introduced to, and thrives in, several regions of the [[western United States]] and in 1966, this squirrel was introduced onto Vancouver Island in Western Canada in the area of Metchosin, and has spread widely from there. They are considered highly invasive and a threat to both the local ecosystem and the native squirrel, the [[American red squirrel]].<ref>{{cite web |date=December 22, 2009 |title=Alien Species Alert! |url=http://www.env.gov.bc.ca/van-island/wildweb/pdf/alien_sp_alert_brochure291009.pdf |access-date=September 19, 2023 |website=Vancouver Island Region Wildlife |publisher=Ministry of Environment and Climate Change Strategy |publication-place=Canada}}</ref>

Overseas, [[eastern gray squirrels in Europe]] are a concern because they have displaced some of the native squirrels there. They have been introduced into Ireland,<ref>{{cite journal |vauthors=McGoldrick M, Rochford J |year=2009 |title=Recent range expansion by the Grey Squirrel (''Sciurus carolinensis'' Gmelin 1788) |journal=[[Irish Naturalists' Journal]] |volume=30 |issue=1 |pages=24–28 |jstor=20764520}}</ref> Britain, Italy, South Africa, and Australia (where it was [[Local extinction|extirpated]] by 1973).<ref name="iucn status 19 November 2021" />

In Ireland, the native squirrel – also colored red – the [[Red squirrel|Eurasian red squirrel]] ''S. vulgaris'' – has been displaced in several eastern counties, though it still remains common in the south and west of the country.<ref>{{Cite book |title=The Irish Squirrel Survey |vauthors=Carey M, Hamilton G, Poole A, Lawton C |publisher=COFORD, National Council for Forest Research and Development |year=2007 |isbn=978-1-902696-60-7 |location=Dublin, Ireland}}</ref>{{Page needed|date=September 2023}} The gray squirrel is also an [[invasive species]] in Britain; it has spread across the country and has largely displaced the red squirrel.<ref name=":0">{{Cite web |last=<!--no author attribution--> |date=<!--not specified on page nor in html--> |title=The Threat |url=https://www.europeansquirrelinitiative.org/the-threat/ |access-date=October 6, 2023 |website=European Squirrel Initiative |publication-place=Suffolk, England}}</ref> That such a displacement might happen in Italy is of concern, as gray squirrels might spread to other parts of [[mainland Europe]].<ref name=":0" /><ref>{{cite web |url=http://www.europeansquirrelinitiative.org/summary.html |title=Summary (of Bertolino S., Lurz. P.W.W., Rushton S.P. 2006, DIVAPRA Entomology & Zoology) |publisher=Europeansquirrelinitiative.org |access-date=10 June 2010 |archive-url=https://web.archive.org/web/20110120003007/http://www.europeansquirrelinitiative.org/summary.html |archive-date=20 January 2011  }}</ref>
[[File:Brown Squirrel 0300 (4327562105).jpg|thumb|Brown morph, in Ontario]]

===Fossil record===
''S. carolinensis'' is known to have occurred at least 18 times throughout the North American [[Pleistocene]] fossil record, across eight different US states,<ref group=note>These are (not counting the single fossil specimen from South Carolina): Florida, Kentucky, Maryland, Missouri, Pennsylvania, Tennessee, Texas, and Virginia.</ref> with some fossils allegedly dating back as early as the late [[Irvingtonian]] period.<ref name="NobodyShouldEverPay167GoddamnEurosForThisBook">{{Cite book|title=Pleistocene Mammals of North America|last1=Kurtén|first1=Björn|last2=Anderson|first2=Elaine|publisher=Columbia University Press|date=September 1980|page=221|quote="The primarily arboreal gray squirrel... has been identified in 18 Pleistocene faunas dating back to the late Irvingtonian (Coleman IIA) in Florida, Kentucky, Maryland, Missouri, Pennsylvania, Tennessee, Texas, and Virginia."|url=https://archive.org/details/pleistocenemamma0000kurt/page/220/mode/2up|isbn=0231037333}}</ref> Body size seems to have increased during the early to middle [[Holocene]] and then decreased to the present size seen today.<ref name="Koprowski"/> 

A single fossil specimen (held and cataloged by [[South Carolina State Museum]]'s natural history collection as SC93.105.172–.174) is known from the [[Harleyville Formation|Ardis local fauna site]] in [[Harleyville, South Carolina]].<ref name="Bentley1994">{{cite journal|last1=Bentley|first1=Curtis C.|last2=Knight|first2=James L.|last3=Knoll|first3=Martin A.|date=December 1994|title=The mammals of the Ardis local fauna (late Pleistocene), Harleyville, South Carolina|journal=Brimleyana|volume=21|access-date=28 March 2024|url=https://www.biodiversitylibrary.org/page/42326537#page/2/mode/1up|url-status=live|archive-url=https://archive.today/20240328151733/https://www.biodiversitylibrary.org/page/42326537%23page/1/mode/1up|archive-date=28 March 2024}}</ref> This specimen consists of a partial [[humerus]] (.172) and two partial [[tibia|tibiae]] (.173, .174), which are anatomically indistinguishable from that of contemporary ''S. carolinensis''.<ref name="Bentley1994"/> Surrounding fossil material from the site has been [[Radiocarbon dating|dated]] back to 18,940–18,530 years ago, during the [[Late Pleistocene]] (late [[Rancholabrean]]) epoch, and indicates that the site was likely a [[Coniferous swamp|hardwood-conifer swamp]] during this time.<ref name="Bentley1994"/>

==Etymology==
The [[genus|generic name]], ''Sciurus'', is derived from two Greek words, ''skia'' 'shadow' and ''oura'' 'tail'. This name alludes to the squirrel sitting in the shadow of its tail.<ref name="hww">{{cite book |author=Hamilton |first=Heather |url=https://www.hww.ca/assets/pdfs/factsheets/eastern-grey-squirrel-en.pdf |title=Eastern Grey Squirrel |publisher=[[Hinterland Who's Who]] |year=1990 |isbn=0-660-13634-1 |editor=Smith, D. |location=Canada |access-date=6 October 2023}}</ref> The [[Specific name (zoology)|specific epithet]], ''carolinensis'', refers to [[the Carolinas]], where the species was first recorded and where the animal is still extremely common. In the United Kingdom and Canada, it is simply referred to as the "grey squirrel". In the US, "eastern" is used to differentiate the species from the [[western gray squirrel]] (''Sciurus griseus'').

==Characteristics==
[[File:Sciurus carolinensis Tracks.jpg|thumb|Bounding tracks in concrete]]
The eastern gray squirrel has predominantly gray [[fur]], but it can have a brownish color. It has a usual white underside as compared to the typical brownish-orange underside of the fox squirrel.<ref>{{cite web|title=New York's Wildlife Resources |url=http://www.dnr.cornell.edu/ext/info/pubs/Wildlife/NYwildlife/gray%20squirrel.pdf |page=2 |publisher=Department of Natural Resources at Cornell University |access-date=28 September 2013  |archive-url=https://web.archive.org/web/20070715134624/http://www.dnr.cornell.edu/ext/info/pubs/Wildlife/NYwildlife/gray%20squirrel.pdf |archive-date=15 July 2007 }}</ref> It has a large bushy tail. Particularly in urban situations where the risk of [[predation]] is reduced, both white-colored<ref>{{cite web|last1=Nelson|first1=Rob|title=White and Albino Squirrel Research Initiative|url=http://www.untamedscience.com/biodiversity/white-squirrel/|website=UntamedScience.com|access-date=23 March 2015}}</ref> and black-colored individuals are quite often found. The [[black squirrel|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. Melanistic squirrels appear to exhibit a higher cold tolerance than the common gray morph; when exposed to −10&nbsp;°C, black squirrels showed an 18% reduction in heat loss, a 20% reduction in basal metabolic rate, and an 11% increase to [[non-shivering thermogenesis]] capacity when compared to the common gray morph.<ref name=Koprowski/> The black coloration is caused by an incomplete dominant mutation of [[MC1R]], where ''E<sup>+</sup>/E<sup>+</sup>'' is a wild type squirrel, ''E<sup>+</sup>/E<sup>B</sup>'' is brown-black, and ''E<sup>B</sup>/E<sup>B</sup>'' is black.<ref name=McRobie2009>{{cite journal | title = The Genetic Basis of Melanism in the Gray Squirrel (Sciurus carolinensis) | year = 2009| doi = 10.1093/jhered/esp059| doi-access = free| last1 = McRobie| first1 = H.| last2 = Thomas| first2 = A.| last3 = Kelly| first3 = J.| journal = Journal of Heredity| volume = 100| issue = 6| pages = 709–714| pmid = 19643815}}</ref>

The head and body length is from {{convert|23|to|30|cm|in|abbr=on}}, the tail from {{convert|19|to|25|cm|in|abbr=on}}, and the adult weight varies between {{convert|400|and|600|g|oz|abbr=on}}.<ref>[[BBC]]: Science and Nature, [https://web.archive.org/web/20090208090853/http://www.bbc.co.uk/nature/wildfacts/factfiles/190.shtml "Grey squirrel: Sciurus carolinensis"]</ref><ref name=MassWild>{{cite web|title=Red & Gray Squirrels in Massachusetts |url=http://www.mass.gov/dfwele/dfw/wildlife/living/living_with_squirrels.htm |work=MassWildlife |publisher=Massachusetts Division of Fisheries and Wildlife |access-date=3 April 2012  |archive-url=https://web.archive.org/web/20130517191120/http://www.mass.gov/dfwele/dfw/wildlife/living/living_with_squirrels.htm |archive-date=17 May 2013 }}</ref> They do not display [[sexual dimorphism]], meaning there is no gender difference in size or coloration.<ref name="ICSRS">{{cite web|title=Basic information about squirrels|url=http://i-csrs.com/basic-information-about-squirrels|website=ICSRS|publisher=Interactive Centre for Scientific Research about Squirrels|access-date=14 April 2017|date=17 November 2015}}</ref>

The tracks of an eastern gray squirrel are difficult to distinguish from the related [[fox squirrel]] and [[Abert's squirrel]], though the latter's range is almost entirely different from the gray's. Like all squirrels, the eastern gray shows four toes on the front feet and five on the hind feet. The hind foot-pad is often not visible in the track. When bounding or moving at speed, the front foot tracks will be behind the hind foot tracks. The bounding stride can be two to three feet long.<ref>Murie, Olaus Johan and Elbroch, Mark (2005). ''Peterson Field Guide to Animal Tracks'', Houghton Mifflin Harcourt, p. 79, {{ISBN|061851743X}}.</ref>

The [[dentition#Dental formula|dental formula]] of the eastern gray squirrel is 1023/1013 (upper teeth/lower teeth).<ref name=Koprowski/>

{{DentalFormula|upper=1.0.2.3|lower=1.0.1.3}} × 2 = 22 total teeth.

Incisors exhibit indeterminate growth, meaning they grow consistently throughout life (as is true for all [[rodent]]s), and their cheek teeth exhibit [[Molar (tooth)#brachydont|brachydont]] (low-crowned teeth) and [[Molar (tooth)#bunodont|bunodont]] (having tubercles on crowns) structures.<ref name=Koprowski/>

{{Multiple image
| image1            = Eastern Grey Squirrel-black.jpg
| caption1          = [[Melanistic]]
| image2            = White leucistic squirrel with a peanut (85668).jpg
| caption2          = [[Leucistic]]
| total_width       = 700
| image3            = Albino Grey Squirrel (25421305328).jpg
| caption3          = [[Albino]]
| align             = center
| header            = Colour mutations
}}

=== Growth and ontogeny ===
[[File:Juvenile sciurus carolinensis 1 (cropped).jpg|thumb|right| Newborn gray squirrel developing fur. They are born hairless and blind.]]
Newborn squirrels are called kits, kittens,<ref>{{Cite web |title=Squirrels in the UK: what they are up to, when and why |url=https://www.nhm.ac.uk/discover/uk-squirrel-behaviour-what-when-and-why.html |access-date=2024-02-07 |website=www.nhm.ac.uk |language=en}}</ref> or pups.<ref>{{Cite web |date=June 2, 2010 |title=Squirrels adopt strays, Canadian study finds |url=http://www.cbc.ca/news/science/squirrels-adopt-strays-canadian-study-finds-1.898990 |website=CBC.ca}}</ref><ref>{{Cite web |title=Eastern Gray Squirrel {{!}} NC State Extension Publications |url=https://content.ces.ncsu.edu/eastern-gray-squirrel-1 |access-date=2024-02-07 |website=content.ces.ncsu.edu |language=en-US}}</ref> They weigh 13–18 grams at birth. They are born [[Blindness_in_animals#Infant_blindness|blind]], entirely hairless, and pink with [[vibrissae]] present at birth. 7–10 days postpartum, the skin begins to darken, just before the juvenile pelage grows in. Lower incisors erupt 19–21 days postpartum, while upper incisors erupt after 4 weeks. Cheek teeth erupt during week 6. Eyes open after 21–42 days, and ears open 3–4 weeks postpartum. Weaning is initiated around 7 weeks postpartum, and is usually finished by week 10, followed by the loss of the juvenile pelage. Full adult body mass is achieved by 8–9 months after birth.<ref name="Koprowski" />

=== Diseases ===
Diseases such as [[typhus]], [[Plague (disease)|plague]], and [[tularemia]] are spread by eastern gray squirrels. If not properly treated, these diseases have the potential to kill squirrels. When bitten or exposed to bodily fluids, humans can contract these diseases. Eastern gray squirrels may also carry parasites such as ringworm, fleas, lice, mites, and ticks which can kill their squirrel host. Their skin may become rough, blotchy, and prone to hair loss due to the mite parasite during the chilly winter months. The parasites are not transferred to people when these squirrels reside in attics or homes.<ref>{{Cite web |title=Eastern Gray Squirrel {{!}} Mid-Atlantic Wildlife Control |url=https://www.midatlanticwildlifecontrol.com/eastern-gray-squirrel/ |access-date=2022-11-03 |website=Best Animal Removal Services - Mid-Atlantic Wildlife Control |language=en-US}}</ref> A frequent illness spread by ticks is [[Lyme disease]].<ref>{{Cite web |title=Lyme disease - Symptoms and causes |url=https://www.mayoclinic.org/diseases-conditions/lyme-disease/symptoms-causes/syc-20374651 |access-date=2022-11-03 |website=Mayo Clinic |language=en}}</ref> Ticks can also spread [[Rocky Mountain spotted fever]]. It can result in damage to internal organs including the heart and kidney if not properly treated.<ref>{{Cite web |title=Rocky Mountain spotted fever - Symptoms and causes |url=https://www.mayoclinic.org/diseases-conditions/rocky-mountain-spotted-fever/symptoms-causes/syc-20361032 |access-date=2022-11-03 |website=Mayo Clinic |language=en}}</ref>  An eastern gray squirrel is susceptible to diseases including [[fibromatosis]] and [[Squirrelpox virus|squirrelpox]]. A squirrel with fibromatosis, a virus-induced illness, may grow massive skin tumors all over the body. Blindness could result from a tumor that is located close to a squirrel's eye.<ref>{{Cite web |last=anirudh |date=2011-06-29 |title=Eastern Gray Squirrel - Facts, Diet, Habitat, Behavior and Pictures |url=https://www.animalspot.net/eastern-gray-squirrel.html |access-date=2022-11-03 |website=Animal Spot |language=en-US}}</ref>

== Behavior and ecology ==
[[File:Sciurus carolinensis -British Columbia, Canada-8.jpg|thumb|Reaching out for food on a garden bird feeder, this squirrel can rotate its hind feet, allowing it to descend a tree head-first.]]

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.<ref name="iucn status 19 November 2021" /> 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 reburial in a more secure site. Others are more permanent and are not retrieved until months later. Each squirrel is estimated to make several thousand caches each season. The squirrels have very accurate [[spatial memory]] for the locations of these caches, using distant and nearby landmarks to retrieve them. [[Olfaction|Smell]] is used partly to uncover food caches, and also to find food in other squirrels' caches. Scent can be unreliable when the ground is too dry or covered in snow.<ref>{{cite web|last1=McCracken|first1=Brian|title=DO SQUIRRELS REALLY KNOW WHERE THEY BURY THEIR FOOD?|url=http://animals.mom.me/squirrels-really-bury-food-11108.html|website=Animals – mom.me}}</ref>

Squirrels sometimes use deceptive behavior to prevent other animals from retrieving cached food. For example, they will pretend to bury the object if they feel that they are being watched. They do this by preparing the spot as usual, for instance, digging a hole or widening a crack, miming the placement of the food, while actually concealing it in their mouths, and then covering up the "cache" as if they had deposited the object. They also hide behind vegetation while burying food or hide it high up in trees (if their rival is not arboreal). Such a complex repertoire suggests that the behaviours are not innate, and imply [[theory of mind]] thinking.<ref>
Grant, Steve (21 October 2004). "[https://www.courant.com/2004/10/21/the-squirrels-bag-of-tricks/ The Squirrel's Bag Of Tricks: They Can't Get Out Of The Way Of Cars, But Other Behaviors Demonstrate Advanced Thinking (for A Rodent)]", ''The Hartford Courant''.</ref><ref>"[http://news.bbc.co.uk/cbbcnews/hi/newsid_7190000/newsid_7193400/7193418.stm Smart squirrels fool food thieves]", ''BBC'', 17 January 2008.</ref>

The eastern gray squirrel is one of very few mammalian species that can descend a tree head-first. It does this by turning its feet so the claws of its hind paws are backward-pointing and can grip the tree bark.<ref>{{cite book|author=Alexander, R. McNeill|title=Principles of animal locomotion|url=https://books.google.com/books?id=2anZacrFaxoC&pg=PA162|year=2003|publisher=Princeton University Press|page=162|isbn=978-0-691-08678-1}}</ref><ref>{{cite web|last1=Nations|first1=Johnathan A.|last2=Link|first2=Olson|title=Scansoriality in Mammals|url=http://animaldiversity.org/collections/scansoriality-in-mammals/|website=Animal Diversity Web}}</ref>

Eastern gray squirrels build a type of [[nest]], known as a [[drey]], in the forks of trees, consisting mainly of dry leaves and twigs. The dreys are roughly spherical, about 30 to 60&nbsp;cm in diameter and are usually insulated with moss, thistledown, dried grass, and feathers to reduce heat loss.<ref name="ICSRS" /> Males and females may share the same nest for short times during the breeding season, and during cold winter spells. Squirrels may share a drey to stay warm. They may also nest in the [[attic]] or exterior walls of a house, where they may be regarded as pests, as well as fire hazards due to their habit of gnawing on electrical cables.<ref>{{Cite web |title=Eastern Grey Squirrel - WildlifeNYC |url=https://www.nyc.gov/site/wildlifenyc/animals/eastern-gray-squirrels.page |access-date=2022-11-03 |website=www.nyc.gov}}</ref> In addition, squirrels may inhabit a permanent tree den hollowed out in the trunk or a large branch of a tree.<ref name="ADW"/>

Eastern gray squirrels exhibit [[Diurnality|diurnal]] or [[crepuscular]] behavior depending on the season,<ref name="MassWild"/> and tend to avoid the heat in the middle of a summer day.<ref name="ADW"/> They do not [[hibernate]].<ref>{{cite web |url=http://www.macclesfield.gov.uk/pdfs/grey_squirrel.pdf |archive-url=https://web.archive.org/web/20060207094417/http://www.macclesfield.gov.uk/pdfs/grey_squirrel.pdf |archive-date=7 February 2006 |title=The Grey Squirrel (''Sciurus carolinensis'')|work=Grey squirrel Advisory |access-date=10 July 2008}}</ref>

===Reproduction===
Eastern gray squirrels can breed twice a year, but younger and less experienced mothers normally have a single litter per year in the spring. Depending on forage availability, older and more experienced females may breed again in summer.<ref>Curtis, Paul D. and Sullivan, Kristi L. (2001) [https://web.archive.org/web/20140117163030/http://www.ccenassau.org/yahoo_site_admin/assets/docs/Squirrel_factsheet.209103258.pdf Tree Squirrels], Wildlife Damage Management Fact Sheet Series, Cornell Cooperative Extension, Ithaca, N.Y.</ref> In a year of abundant food, 36% of females bear two litters, but none will do so in a year of poor food.<ref name=Koprowski>{{cite journal|last=Koprowski|first=John L.|title=''Sciurus carolinensis''|journal=Mammalian Species|date=1994|issue=480|pages=1–9|url=http://www.science.smith.edu/msi/pdf/i0076-3519-480-01-0001.pdf|access-date=26 March 2014|doi=10.2307/3504224|jstor=3504224|archive-url=https://web.archive.org/web/20140327221219/http://www.science.smith.edu/msi/pdf/i0076-3519-480-01-0001.pdf|archive-date=27 March 2014}}</ref> Their breeding seasons are December to February and May to June, though this is slightly delayed in more northern latitudes.<ref name="MassWild"/><ref name="ADW"/> The first litter is born in February or March, the second in June or July, though, again, bearing may be advanced or delayed by a few weeks depending on climate, temperature, and forage availability. In any given breeding season, an average of 61 – 66% of females bear young.<ref name="Koprowski" /> If a female fails to conceive or loses her young to unusually cold weather or predation, she re-enters estrus and has a later litter. Five days before a female enters estrus, she may attract up to 34 males from up to 500 meters away. Eastern gray squirrels exhibit a form of polyandry, in which the competing males will form a hierarchy of dominance, and the female will mate with multiple males depending on the hierarchy established.<ref name=Koprowski/>

[[File:Squirrels drey.JPG|thumb|right|Eastern gray squirrel drey]]
Normally, one to four young are born in each litter, but the largest possible litter size is eight.<ref name="Koprowski" /> The [[gestation]] period is about 44 days.<ref name="Koprowski" /> The young are [[Weaning|weaned]] around 10 weeks, though some may wean up to six weeks later in the wild. They begin to leave the nest after 12 weeks, with autumn born young often wintering with their mother. Only one in four squirrel kits survives to one year of age, with mortality around 55% for the following year. Mortality rates then decrease to around 30% for following years until they increase sharply at eight years of age.<ref name="Koprowski" />

Rarely, eastern gray females can enter estrus as early as five and a half months old,<ref name="ADW">{{cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Sciurus_carolinensis.html |title=''Sciurus carolinensis'' |author=Lawniczak, M. |year=2002 |publisher=[[Animal Diversity Web]] |access-date=10 July 2008}}</ref> but females are not normally fertile until at least one year of age. Their mean age of first estrus is 1.25 years.<ref name="Koprowski" /> The presence of a fertile male will induce ovulation in a female going through estrus.<ref name=Koprowski/> Male eastern grays are sexually mature between one and two years of age.<ref>{{Cite journal
 | pmid = 4018551
| year = 1985
| last1 = Webley
| first1 = G. E.
| title = Seasonal changes in the testes and accessory reproductive organs and seasonal and circadian changes in plasma testosterone concentrations in the male grey squirrel (''Sciurus carolinensis'')
| journal = General and Comparative Endocrinology
| volume = 59
| issue = 1
| pages = 15–23
| last2 = Pope
| first2 = G. S.
| last3 = Johnson
| first3 = E
| doi = 10.1016/0016-6480(85)90414-9
}}</ref> Reproductive longevity for females appears to be over 8 years, with 12.5 years documented in North Carolina.<ref name=Koprowski/> These squirrels can live to be 20 years old in captivity, but in the wild live much shorter lives due to predation and the challenges of their habitat. At birth, their life expectancy is 1–2 years, an adult typically can live to be six, with exceptional individuals making it to 12 years.

===Communication===
[[File:Grey Squirrel (Sciurus carolinensis) (W1CDR0001470 BD12).ogg|left|thumb|Calls recorded in Surrey, England]]
As in most other mammals, communication among eastern gray squirrel individuals involves both vocalizations and posturing. The species has a quite varied repertoire of vocalizations, including a squeak similar to that of a mouse, a low-pitched noise, a chatter, and a raspy "mehr mehr mehr". Other methods of communication include tail-flicking and other gestures, including facial expressions. Tail flicking and the "kuk" or "quaa" call are used to ward off and warn other squirrels about predators, as well as to announce when a predator is leaving the area.<ref name="Kelly" /> Squirrels also make an affectionate coo-purring sound that biologists call the "muk-muk" sound. This is used as a contact sound between a mother and her kits and in adulthood, by the male when he courts the female during mating season.<ref name=Kelly>{{cite news|last=Kelly|first=John|title=Learn to speak squirrel in four easy lessons|url=https://www.washingtonpost.com/local/learn-to-speak-squirrel-in-four-easy-lessons/2012/04/09/gIQAV8Jr6S_story.html|access-date=7 March 2014|newspaper=Washington Post|date=9 April 2012}}</ref> The use of vocal and visual communication has been shown to vary by location, based on elements such as [[noise pollution]] and the amount of open space. For instance, populations living in large cities generally rely more on the visual signals, due to the generally louder environment with more areas without much visual restriction. However, in heavily wooded areas, vocal signals are used more often due to the relatively lower noise levels and a dense canopy restricting visual range.<ref>{{cite journal |url=http://www.currentzoology.org/temp/%7B9776C11E-254E-42C9-8B99-06749C919867%7D.pdf |journal=Current Zoology |year=2010 |volume=56 |issue=3 |pages=313–326 |title=Multimodal alarm behavior in urban and rural gray squirrels studied by means of observation and a mechanical robot |author=Partan, Sarah R. |doi=10.1093/czoolo/56.3.313 |doi-access=free |access-date=7 March 2014 |archive-date=18 June 2018 |archive-url=https://web.archive.org/web/20180618152733/http://www.currentzoology.org/temp/%7B9776C11E-254E-42C9-8B99-06749C919867%7D.pdf |url-status=dead }}</ref>

=== Habitat ===
[[File:Eastern Gray Squirrels (Sciurus carolinensis), Family - Mississauga 02.jpg|thumb|Eastern gray squirrel staying in a birdhouse]]
In the wild, eastern gray squirrels can be found inhabiting large areas of mature, dense [[woodland]] ecosystems, generally covering 100 acres (40 hectares) of land.<ref name="ADW" /> These forests usually contain large [[Mast (botany)|mast]]-producing trees such as oaks and hickories, providing ample food sources. Oak-hickory hardwood forests are generally preferred over coniferous forests due to the greater abundance of mast forage.<ref name="MassWild" /> This is why they are found only in parts of eastern Canada which do not contain boreal forest (i.e. they are found in some parts of New Brunswick, in southwestern Quebec, throughout southern Ontario and in southern Manitoba).{{Ambiguous|date=April 2023}}

Eastern gray squirrels generally prefer constructing their dens upon large tree branches and within the hollow trunks of trees. They also have been known to take shelter within abandoned bird nests. The dens are usually lined with moss plants, thistledown, dried grass, and feathers. These perhaps provide and assist in the insulation of the den, used to reduce heat loss. A cover to the den is usually built afterwards.<ref>{{Cite web |title=Eastern Gray Squirrel |url=https://www.projectnoah.org/spottings/10395086 |access-date=2022-10-11 |website=Project Noah}}</ref> Eastern gray squirrels also use dens for protection from predators and to help them look after their young. Young survive 40 percent less if they lived in a leaf nest compared to a den. Squirrels tend to claim 2-3 dens at the same time. Canopy and midstory trees are used by squirrels to hide from predators such as hawks and owls. The typical squirrel ranges over {{convert|1.5|to|8|acre|ha}} and tends to be smaller where more of them are found.<ref name="content.ces.ncsu.edu" />

Close to human settlements, eastern gray squirrels are found in parks and back yards of houses within urban environments and in the farmlands of rural environments.<ref>{{cite web |title=The Leading America Zoo Site on the Net |url=http://www.americazoo.com/goto/index/mammals/140.htm |access-date=30 October 2011 |publisher=americazoo.com}}</ref>

=== Ecosystem ===
Eastern gray squirrels forage tree seeds and disperse them through seed-caching. They may also contribute to the distribution of truffle fungal spores when they eat truffles. They are an important prey source and parasitic host for other animals.<ref>{{Cite web |last=Lawniczak |first=Mara Katharine |title=Sciurus carolinensis (eastern gray squirrel) |url=https://animaldiversity.org/accounts/Sciurus_carolinensis/ |access-date=2024-02-12 |website=Animal Diversity Web |language=en}}</ref> 

===Predation===
Eastern gray squirrels predators include [[Accipitridae|hawks]], [[Mustelidae|weasels]], [[raccoon]]s, [[bobcat]]s, [[fox]]es, [[Cat|domestic]] and [[feral cat]]s, [[snake]]s, [[owl]]s, and [[dog]]s.<ref name=":1" /><ref name="ADW" /> Their primary predators are hawks, owls, and snakes.<ref>{{Cite web |last=Watson |first=Jessica |date=2022-08-09 |title=What Impact Does The Eastern Gray Squirrel Have Economic ? Find Out Here Squirrel Arena |url=https://www.squirrelarena.com/what-impact-does-the-eastern-gray-squirrel-have-economic/ |access-date=2022-11-21 |website=www.squirrelarena.com |language=en-US}}</ref> Raccoons and weasels may consume a squirrel depending on where it lives in the United States.<ref name="All of the Types of Squirrels">{{Cite web |title=All of the Types of Squirrels |url=https://sciencing.com/types-squirrels-8209821.html |access-date=2022-11-20 |website=Sciencing |language=en}}</ref> Rattlesnakes eat squirrels in California as they are searching for food in a heavy forest.<ref name="All of the Types of Squirrels" /> The squirrel is susceptible to being eaten by foxes in the eastern region of the United States.<ref name="All of the Types of Squirrels" />

In its introduced range in South Africa, it has been preyed on by [[African harrier-hawk]]s.<ref>{{cite web |title=Polyboroides typus (African harrier-hawk, Gymnogene) |url=http://www.biodiversityexplorer.org/birds/accipitridae/polyboroides_typus.htm  |archive-url=https://web.archive.org/web/20131103175811/http://www.biodiversityexplorer.org/birds/accipitridae/polyboroides_typus.htm |archive-date=3 November 2013 |access-date=29 June 2013 }}</ref> When a predator is approaching the eastern gray squirrel, other squirrels will inform the squirrel of the predator by sending an acoustic signal to let the squirrel know. The speed of a squirrel makes it hard for it to be captured by the predators.<ref>{{Cite web |title=Eastern Gray Squirrel |url=https://www.chesapeakebay.net/discover/field-guide/entry/eastern-gray-squirrel |access-date=2022-10-11 |website=Chesapeake Bay |language=en-US}}</ref>

== Diet ==
[[File:Hazelnuts gnawed by Grey Squirrel.jpg|thumb|Hazelnuts gnawed by gray squirrel; the curved cut marks left by the sharp incisors are visible around the holes]]

Eastern gray squirrels eat a range of foods, such as tree bark, tree [[bud]]s, flowers,<ref name="animaldiversity.org">{{Cite web|url=https://animaldiversity.org/accounts/Sciurus_carolinensis/|title=Sciurus carolinensis (eastern gray squirrel)|first=Mara Katharine|last=Lawniczak|website=Animal Diversity Web}}</ref> berries, many types of [[seed]]s and [[acorn]]s, [[walnut]]s, and other [[nut (fruit)|nuts]], like hazelnuts (see picture) and some types of [[fungi]] found in the forests, including [[Amanita muscaria|fly agaric]] mushrooms<ref name="Long1995" /> and [[truffle]]s.<ref name="ADW" /> They can cause damage to trees by tearing the bark and eating the soft [[Cambium|cambial tissue]] underneath. In Europe, [[Acer pseudoplatanus|sycamore]] and [[Fagus sylvatica|beech]] suffer the greatest damage.<ref>Butler, F. and Kelleher, C. (eds) 2012. ''All-Ireland Mammal Symposium 2009. '' Irish Naturalists' Journal, Belfast, {{ISBN|978-0-9569704-1-1}}</ref> [[Mast (botany)|Mast]]-bearing [[gymnosperm]]s such as [[Cedrus|cedar]], [[Tsuga|hemlock]], [[pine]], and [[spruce]] are another food source,<ref name="animaldiversity.org" /> as well as [[angiosperm]]s such as [[hickory]], [[oak]], and [[Juglans|walnut]]. These trees produce important foods for them during the spring and fall months. The squirrels will vary the species they forage from depending on the season.<ref name="content.ces.ncsu.edu">{{Cite web |title=Eastern Gray Squirrel {{!}} NC State Extension Publications |url=https://content.ces.ncsu.edu/eastern-gray-squirrel |access-date=2022-11-19 |website=content.ces.ncsu.edu |language=en-US}}</ref> The squirrels also raid gardens for [[wheat]],<ref name="animaldiversity.org" /> [[tomato]]es, [[corn]], [[Strawberry|strawberries]], and other garden crops.<ref>{{cite web|title=How to Manage Pests – Tree Squirrels|url=http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74122.html|publisher=University of California|access-date=23 May 2014}}</ref> Sometimes they eat the tomato seeds and discard the rest. On occasion, eastern gray squirrels also prey upon [[insects]], [[frogs]], small rodents including other squirrels, and small birds, their eggs, and young.<ref name="iucn status 19 November 2021" /><ref name="ADW" /> They also gnaw on bones, [[antler]]s, and turtle shells – likely as a source of minerals scarce in their normal diet.<ref name="Long1995">{{cite book|author=Long, Kim |title=Squirrels: a wildlife handbook|url=https://books.google.com/books?id=tznNYj4mTs0C|page=95|date=September 1995|publisher=Big Earth Publishing|isbn=978-1-55566-152-6}}</ref> In urban and suburban areas, these squirrels scavenge for food in trash bins. However, these foods are not safe for them to digest because they include sugar, fat, as well as additives that can make them sick. Eastern gray squirrels are sometimes mistakenly thought to be herbivores, but they are omnivores.<ref>{{Cite web |last=Warner |first=Monique |date=2022-06-28 |title=Are Squirrels Omnivores, Herbivores Or Carnivores? |url=https://misfitanimals.com/squirrels/are-squirrels-omnivores/ |access-date=2022-11-21 |language=en-US}}</ref>

Eastern gray squirrels have a high enough tolerance for humans to inhabit residential neighborhoods and raid [[bird feeder#Squirrels|bird feeder]]s for [[millet]], corn, and [[sunflower seed]]s. Some people who feed and watch birds for entertainment also intentionally feed seeds and nuts to the squirrels for the same reason.<ref name="isbn_9781555661526">{{Citation |last=Long |first=Kim |year=1995 |title=Squirrels: A Wildlife Handbook |publisher=Johnson Books|pages=144–146 |url=https://books.google.com/books?id=UPZEF-Nhs9gC |isbn=978-1-55566-152-6 |postscript=.}}</ref> However, in the UK eastern gray squirrels can take a significant proportion of supplementary food from feeders, preventing access and reducing use by wild birds.<ref>{{cite journal|last1=Hanmer|first1=Hugh J.|last2=Thomas|first2=Rebecca L.|last3=Fellowes|first3=Mark D. E.|title=Introduced Grey Squirrels subvert supplementary feeding of suburban wild birds|journal=Landscape and Urban Planning|volume=177|pages=10–18|doi=10.1016/j.landurbplan.2018.04.004|year=2018|bibcode=2018LUrbP.177...10H | s2cid=90663919 |url=http://centaur.reading.ac.uk/76790/1/Squirrels_on_feeders_MDEF%20final%20full.pdf}}</ref> Attraction to supplementary feeders can increase local bird nest predation, as eastern gray squirrels are more likely to forage near feeders, resulting in increased likelihood of finding nests, eggs and nestlings of small passerines.<ref>{{cite journal|last1=Hanmer|first1=Hugh J.|last2=Thomas|first2=Rebecca L.|last3=Fellowes|first3=Mark D. E.|title=Provision of supplementary food for wild birds may increase the risk of local nest predation|journal=Ibis|volume=159|issue=1|pages=158–167|doi=10.1111/ibi.12432|year=2017|url=http://centaur.reading.ac.uk/68066/3/Ibis%20paper%20final%20complete.pdf}}</ref>

{{Multiple image
| image1            = Squirrel eating cicada.ogg
| caption1          = Eating a cicada
| image2            = Eastern Gray Squirrel, Louisiana, US imported from iNaturalist photo 411198365.jpg
| caption2          = Eating a mushroom
| image3            = Squirrel eating goats head.jpg
| image4            = Squirrel eating a bird.JPG
| caption3          = Eating a goat skull
| caption4          = Eating a bird
| image5            = Grey squirrel 2.jpg
| image6            = Squirrel (36127639150).jpg
| image7            = Eastern Grey Squirrel with Acorns.jpg
| image8            = Squirrel eating an ice cream cone (3558009610).jpg
| align             = center
| perrow            = 4/4
| total_width       = 900
| caption5          = Eating an apple
| caption6          = Eating a conifer cone
| caption7          = Eating an acorn
| caption8          = Eating an ice cream cone
}}

== Introductions and impact ==
[[File:Eastern Grey Squirrel in Bunhill Fields.jpg|thumb|The eastern gray squirrel is considered an [[invasive species]] in the UK (Bunhill Fields, London)]]
The eastern gray squirrel is an [[introduced species]] in a variety of locations in western North America: in [[western Canada]], to the southwest corner of British Columbia and to the city of Calgary, Alberta;<ref name=hww/> in the United States, to the states of [[Washington (state)|Washington]] and [[Oregon]] and, in [[California]], to the city of [[San Francisco]] and the [[San Francisco Peninsula]] area in [[San Mateo County, California|San Mateo]] and [[Santa Clara County, California|Santa Clara]] Counties, south of the city. It has become the most common squirrel in many urban and suburban habitats in western North America, from north of central California to southwest British Columbia.

By the turn of the 20th century, breeding populations of the eastern gray squirrel had been introduced into [[South Africa]], [[Ireland]], [[Italy]], [[Australia]] (extirpated by 1973), and the [[United Kingdom]].<ref>Long, J. L. (2003). Introduced Mammals of the World: Their History, Distribution and Influence. Csiro Publishing, Collingwood, Australia. {{ISBN|9780643099166}}</ref>

In South Africa, though exotic, it is not usually considered an [[invasive species]] owing to its small range (only found in the extreme southwestern part of the Western Cape, going north as far as the small farming town of [[Franschhoek]]), as well because it inhabits urban areas and places greatly affected by humans, such as agricultural areas and exotic pine plantations. Here, it mostly eats acorns and pine seeds, although it will take indigenous and commercial fruit, as well.<ref>{{cite web |url=http://home.intekom.com/ecotravel/Guides/Wildlife/Vertebrates/Mammals/Smaller/Grey_Squirrel.htm |title=The Grey Squirrel – Sciurus carolinensis of Southern Africa |publisher=Home.intekom.com |access-date=10 June 2010 |archive-date=25 December 2019 |archive-url=https://web.archive.org/web/20191225092348/http://home.intekom.com/ecotravel/Guides/Wildlife/Vertebrates/Mammals/Smaller/Grey_Squirrel.htm  }}</ref> Even so, it is unable to use the natural vegetation ([[fynbos]]) found in the area, a factor which has helped to limit its spread.<ref>{{cite web |url=http://www.biodiversityexplorer.org/mammals/rodentia/sciurus_carolinensis.htm |title=Sciurus carolinensis (Grey Squirrel) |publisher=Biodiversityexplorer.org |access-date=10 June 2010 |archive-date=9 September 2018 |archive-url=https://web.archive.org/web/20180909154924/http://www.biodiversityexplorer.org/mammals/rodentia/sciurus_carolinensis.htm  }}</ref> It does not come into contact with native squirrels due to geographic isolation (a native tree squirrel, ''[[Paraxerus cepapi]]'', is found only in the savanna regions in the northeast of the country)<ref>{{cite web|url=http://www.krugerpark.co.za/africa_tree_squirrel.html |title=Tree Squirrel &#124; Rodent &#124; Southern Africa |publisher=Krugerpark.co.za |access-date=10 June 2010}}</ref> and different habitats.

Gray squirrels were first introduced to Britain in the 1870s, as fashionable additions to estates.<ref name=tele>{{cite news |title=History of grey squirrels in UK |url=https://www.telegraph.co.uk/news/earth/wildlife/10705527/History-of-grey-squirrels-in-UK.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/earth/wildlife/10705527/History-of-grey-squirrels-in-UK.html |archive-date=12 January 2022 |url-access=subscription |url-status=live |access-date=2018-09-01 |work=Daily Telegraph (UK) |date=2018-08-28}}{{cbignore}}</ref> In 1921 it was reported in ''[[The Times]]'' that the [[Zoological Society of London]] had released eastern greys to breed at liberty in [[Regents Park]]:

{{blockquote|text= A dozen years ago the Zoological Society of London obtained a number from a private collection in Bedfordshire for the purpose of inducing them to breed at liberty in the Gardens in Regent's Park. They were first kept in a large enclosure from which, when they had become used to visitors, they were allowed to pass in and out by a rope bridge to a tree. It was hoped that they would spread from the Gardens to the Park. After two or three years in which they seemed to be disappearing, they suddenly became ubiquitous...The grey squirrels are plainly happy and plainly give happiness to Londoners...On the other hand, grey squirrels, whether by taking advantage of tubes and buses, or by deliberate human connivance, have spread from London and are invading the country over very wide areas. They are said to drive out the red squirrel, to raid gardens, and to add to the anxieties of the pheasant breeder. We hope that fuller inquiry will not sustain these charges.<ref>{{cite news |last1=Anon |title=The success of grey squirrels|work=The Times |publisher=Times Newspapers Limited |date=December 20, 1921}}</ref>}}
They spread rapidly across England, and then became established in both Wales and parts of southern Scotland. On mainland Britain, they have almost entirely displaced native red squirrels. Larger than red squirrels and capable of storing up to four times more fat, gray squirrels are better able to survive winter conditions. They produce more young and can live at higher densities. Gray squirrels also carry the [[squirrel parapoxvirus|squirrelpox virus]], to which red squirrels have no immunity. When an infected gray squirrel introduces squirrelpox to a red squirrel population, its decline is 17–25 times greater than through competition alone.<ref name=tele/>

In Ireland, the displacement of red squirrels has not been as rapid because only a single introduction occurred, in [[County Longford]]. Schemes have been introduced to control the population of gray squirrels in Ireland to encourage the native red squirrels. Eastern gray squirrels have also been introduced to Italy, and the [[European Union]] has expressed concern that they will similarly displace the red squirrel from parts of the European continent.
[[File:Problems at Dodd Wood (19534706210).jpg|thumb|An eastern gray squirrel and a red squirrel eating seeds]]

=== As food ===
{{main|Tree squirrel#As game}}

Gray squirrels were eaten in earlier times by Native Americans and their meat is still popular with hunters across most of their range in North America. Today, it is still available for human consumption and is occasionally sold in the United Kingdom.<ref>[http://www.economist.com/node/21548935 "Wild meat: Squirrel nutcase"]. The Economist, Vol. 402 Number 8772 (3 March 2012).</ref> However, physicians in the United States have warned that squirrel brains should not be eaten, because of the risk that they may carry [[Creutzfeldt–Jakob disease]].<ref>{{cite news |last=Blakeslee |first=Sandra |date=27 August 1997 |title=Kentucky Doctors Warn Against a Regional Dish: Squirrels' Brains |work=The New York Times |url=https://www.nytimes.com/1997/08/29/us/kentucky-doctors-warn-against-a-regional-dish-squirrels-brains.html |access-date=15 February 2017}}</ref>

=== Displacement of red squirrels ===
{{Further|Eastern gray squirrels in Europe}}
In Britain and Ireland, the eastern gray squirrel is not regulated by natural predators,<ref>[https://web.archive.org/web/20070220105555/http://www.forestry.gov.uk/forestry/infd-6l4fdh The grey squirrel policy and action statement]. forestry.gov.uk</ref> other than the [[European pine marten]], which is generally absent from England and Wales.<ref name=BC>{{cite journal|title=Population crash in an invasive species following the recovery of a native predator: the case of the American grey squirrel and the European pine marten in Ireland|journal=Biodiversity and Conservation|date=March 2014|volume=23|issue=3|pages=753–774|doi=10.1007/s10531-014-0632-7|last1=Sheehy|first1=Emma|last2=Lawton|first2=Colin|bibcode=2014BiCon..23..753S |s2cid=10449048}}</ref> This has aided its rapid population growth and has led to the species being classed as a [[pest (organism)|pest]] and it is now illegal to release captured eastern grey squirrels back into the wild in the UK.<ref>{{cite web |title=March 2019 update: Invasive non-native species and grey squirrels |url=https://www.gov.uk/government/news/march-2019-update-invasive-non-native-species-and-grey-squirrels |website=Gov.uk |access-date=14 February 2024}}</ref> Measures are being devised to reduce its numbers, including a campaign starting in 2006 named "Save Our Squirrels" using the slogan "Save a red, eat a grey!" which attempted to re-introduce squirrel meat in to the local market, with celebrity chefs promoting the idea,<ref>{{cite news|date=23 March 2006|title=Jamie 'must back squirrel-eating'|work=BBC News|url=http://news.bbc.co.uk/1/hi/uk_politics/4835690.stm|access-date=22 August 2007}}</ref> cookbooks introducing recipes containing squirrel and the [[Forestry Commission]] providing a regular supply of squirrel meat to British restaurants, factories and butchers.<ref>{{Cite news|last=Spieler|first=Marlena|date=2009-01-06|title=Saving a Squirrel by Eating One|language=en-US|work=The New York Times|url=https://www.nytimes.com/2009/01/07/dining/07squirrel.html|access-date=2021-12-13|issn=0362-4331}}</ref> In areas where [[Relict (biology)|relict]] populations of [[red squirrel]]s survive, such as the islands of [[Anglesey]], [[Brownsea]] and the [[Isle of Wight]], programs exist to eradicate gray squirrels and prevent them from reaching these areas in order to allow red squirrel populations to recover and grow.<ref>{{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 |access-date=22 August 2007}}</ref>

Although complex and controversial, the main factor in the eastern gray squirrel's displacement of the red squirrel is thought to be its greater [[fitness (biology)|fitness]], hence a competitive advantage over the red squirrel on all measures.<ref>{{cite journal |author1=Wauters, L. A. |author2=Gurnell, J. |author3=Martinoli, A. |author4=Tosi, G. |name-list-style=amp|year=2002 |title=Interspecific competition between native Eurasian red squirrels and alien grey squirrels: does resource partitioning occur? |journal=Behavioral Ecology and Sociobiology |volume=52 |pages=332–341 |doi=10.1007/s00265-002-0516-9 |issue=4|s2cid=44051537 }}</ref> Within 15 years of the grey squirrel's introduction to a red squirrel habitat, red squirrel populations are extinct.<ref name="daera-ni.gov.uk">{{Cite web |date=2015-08-24 |title=Controlling the grey squirrel population {{!}} Department of Agriculture, Environment and Rural Affairs |url=https://www.daera-ni.gov.uk/articles/controlling-grey-squirrel-population |access-date=2022-11-19 |website=DAERA |language=en}}</ref> The eastern gray squirrel tends to be larger and stronger than the red squirrel and has been shown to have a greater ability to store fat for winter. Due to the dearth of trees in their native Ireland for them to reside in, red squirrels are the only species being harmed by the invasion of grey squirrels.<ref name="daera-ni.gov.uk"/> The squirrel can, therefore, compete more effectively for a larger share of the available food, resulting in relatively lower survival and breeding rates among the red squirrel. [[Parapoxvirus]] may also be a strongly contributing factor; red squirrels have long been fatally affected by the disease, while the eastern gray squirrels are unaffected, but thought to be carriers – although how the virus is transmitted has yet to be determined. Red squirrel extinction rates can be 20–25 times greater in areas with confirmed cases of squirrel pox than they are in areas without the disease.<ref name="daera-ni.gov.uk"/> This competitive action done between these two squirrels is reasoned to qualify the eastern gray squirrel as a keystone species because since the eastern gray squirrel is coming and wiping out the red squirrels, there would be a reduced chance of competition hence more eastern gray squirrels will come in to Ireland.<ref>{{Cite book |last=Molles |first=Manuel C. Jr. |title=Ecology: concepts and applications |date=2019 |others=Anna Sher |isbn=978-1-259-88005-6 |edition=Eighth |location=New York, NY |oclc=1010579815}}</ref> However, several cases of red squirrels surviving have been reported, as they have developed an immunity – although their population is still being massively affected. The red squirrel is also less tolerant of [[habitat destruction]] and fragmentation, which has led to its population decline, while the more adaptable eastern gray squirrel has taken advantage and expanded. Methods done to control this competition between these squirrels are that red squirrels should remain in their original habitats, such as Ireland, while the grey squirrels should be kept out of these places entirely as a means of controlling this squirrel competition.<ref name="daera-ni.gov.uk"/>

Similar factors appear to have been at play in the Pacific region of North America, where the native [[American red squirrel]] has been largely displaced by the eastern gray squirrel in parks and forests throughout much of the region.

Ironically, "fears" for the future of the eastern gray squirrel arose in 2008, as the [[melanistic]] form (black) began to spread through the southern British population.<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/7839653.stm |title=Black squirrels set to dominate |work=BBC News |date=20 January 2009 |access-date=30 October 2011}}</ref> In the UK, if a "grey squirrel" (eastern gray squirrel) is trapped, under the [[Wildlife and Countryside Act 1981]], it is illegal to release it or to allow it to escape into the wild; instead, it is legally required be "humanely dispatched."<ref>{{cite web|url=http://defra.gov.uk/rds/publications/technical/TAN_09.pdf|archive-url=http://webarchive.nationalarchives.gov.uk/20070701131656/defra.gov.uk/rds/publications/technical/TAN_09.pdf|archive-date=1 July 2007|title=Defra Rural Development Service Technical Advice Note 09}}</ref>

In the late 1990s, Italy's National Wildlife Institute and University of Turin launched an eradication attempt to halt the spread of gray squirrels in northwest Italy, but court action by animal rights groups blocked this. Hence gray squirrels are expected to cross the Alps into France and Switzerland in the next few decades.<ref>{{cite journal|doi=10.1016/S0006-3207(02)00161-1|title=Spread and attempted eradication of the grey squirrel (''Sciurus carolinensis'') in Italy, and consequences for the red squirrel (''Sciurus vulgaris'') in Eurasia|year=2003|url=http://planet.botany.uwc.ac.za/NISL/Invasives/Refs/BertolinoandGenovesi.pdf|last1=Bertolino|first1=Sandro|last2=Genovesi|first2=Piero|journal=Biological Conservation|volume=109|issue=3|pages=351–358|bibcode=2003BCons.109..351B|access-date=19 October 2020|archive-date=21 August 2022|archive-url=https://web.archive.org/web/20220821061324/https://planet.botany.uwc.ac.za/NISL/Invasives/Refs/BertolinoandGenovesi.pdf|url-status=dead}}</ref><ref>United Nations Environment Programme World Conservation Monitoring Centre (2010) [https://ec.europa.eu/environment/cites/pdf/reports/grey_squirrel.pdf Review of the Grey Squirrel ''Sciurus carolinensis'']. UNEP-WCMC, Cambridge</ref>

==See also==
{{Portal|Mammals}}
* [[Black squirrel]], a melanistic subgroup 
* [[Western gray squirrel]] (''Sciurus griseus'')
* [[Arizona gray squirrel]] (''Sciurus arizonensis'')
* [[Mexican gray squirrel]] (''Sciurus aureogaster'')
* [[Tommy Tucker (squirrel)]], a celebrity eastern gray squirrel in the 1940s
* [[Pinto Bean (squirrel)]], a piebald eastern gray squirrel in Illinois that died in 2022
* [[Peanut (squirrel)]], an eastern gray which became famous on social media and was then controversially killed in 2024

==References==
{{reflist|group=note}}
{{Reflist|30em}}

==External links==
{{sister project links|auto=1}}
* [https://web.archive.org/web/20080524045446/http://www.arkive.org/species/ARK/mammals/Sciurus_carolinensis/ ARKive] – Still photos and videos
* [https://www.washingtonpost.com/wp-dyn/content/article/2005/05/18/AR2005051802251.html An Exotic Evolution: Black Squirrels Imported in Early 1900s Gain Foothold] – an article from [[The Washington Post]]
* [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]
* [https://www.youtube.com/watch?v=VS3_sfdUxvM Grey Squirrel feeding on peanuts in a British park]
* [http://ofnc.ca/programs/fletcher-wildlife-garden/flora-and-fauna-at-the-fwg/grey-squirrels-at-the-fwg Grey Squirrels], Fletcher Wildlife Garden

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{{North American Game}}

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[[Category:Sciurus|Eastern gray squirrel]]
[[Category:Extant Late Pleistocene first appearances]]
[[Category:Pleistocene mammals of North America]]
[[Category:Rodents of Canada]]
[[Category:Rodents of the United States]]
[[Category:Mammals described in 1788|Eastern gray squirrel]]
[[Category:Taxa named by Johann Friedrich Gmelin|Eastern gray squirrel]]
[[Category:Symbols of North Carolina]]