:Squirrel

The word squirrel, first attested in 1327, comes from the Anglo-Norman {{lang|xno|esquirel}} which is from the Old French {{lang|fro|escurel}}, the reflex of a Latin word {{lang|la|sciurus}}, which was taken from the Ancient Greek word {{lang|grc|σκίουρος}} ({{transliteration|grc|skiouros}}; from {{lang|grc|σκία-ουρος}}) 'shadow-tailed', referring to the long bushy tail which many of its members have.{{cite encyclopedia | encyclopedia =The Oxford English Dictionary | title = squirrel, n. | url = http://dictionary.oed.com/cgi/entry/50235460 | access-date =8 November 2010 | edition = 2nd. | year = 1989 | publisher = Oxford University Press}}{{sfn|Whitaker|Elman|1980|p=370}} Sciurus is also the name of one of its genuses.{{sfn|Whitaker|Elman|1980|p=370}}

The native Old English word for the squirrel, {{lang|ang|ācweorna}}, only survived into Middle English (as {{lang|enm|aquerne}}) before being replaced.{{cite web | url=http://www.etymonline.com/index.php?term=squirrel | title=Squirrel | work=Online Etymology Dictionary | access-date=7 February 2008}} The Old English word is of Common Germanic origin, cognates of which are still used in other Germanic languages, including the German {{lang|de|Eichhörnchen}} (diminutive of {{lang|de|Eichhorn}}, which is not as frequently used); the Norwegian {{lang|no|ikorn}}/{{lang|no|ekorn}}; the Dutch {{lang|nl|eekhoorn}}; the Swedish {{lang|sv|ekorre}} and the Danish {{lang|da|egern}}.

A group of squirrels is called a "dray"{{Cite book|last=Lipton|first=James|url=https://books.google.com/books?id=AVNazQEACAAJ|title=An Exaltation of Larks|date=1991|publisher=Viking|isbn=978-0-670-30044-0|language=en}} or a "scurry".Universe in Your Pocket by Joel Levy, published by Barnes & Noble, Inc.

File:Sciurus carolinensis -British Columbia, Canada-8.jpg

File:Ratufa skull.JPG (genus Ratufa)—note the classic sciuromorphous shape of the anterior zygomatic region.]]

Squirrels are generally small animals, ranging in size from the African pygmy squirrel and least pygmy squirrel at {{cvt|10-14|cm}} in total length and just {{cvt|12-26|g}} in weight,{{cite book | author=Kingdon, J. | author-link=Jonathan Kingdon | year=1997 | title=The Kingdon Guide to African Mammals | publisher=Academic Press Limited, London | isbn=0-12-408355-2 | url-access=registration | url=https://archive.org/details/kingdonfieldguid00jona }}{{cite book| author1=Payne, J. | author2=C.F. Francis | year=1998 | title=A Field Guide to the Mammals of Borneo | page=243 | publisher=The Sabah Society | edition=3 | isbn=967-99947-1-6 }} to the Bhutan giant flying squirrel at up to {{cvt|1.27|m}} in total length,{{cite journal | author=Choudhury, A. | year=2002 | title=Petaurista nobilis singhei: First record in India and a note on its taxonomy | journal=The Journal of the Bombay Natural History Society | volume=99 | issue=1 | pages=30–34 }} and several marmot species, which can weigh {{cvt|8|kg}} or more.{{cite journal | author1=Kryštufek, B. | author2=B. Vohralík | year=2013 | title=Taxonomic revision of the Palaearctic rodents (Rodentia). Part 2. Sciuridae: Urocitellus, Marmota and Sciurotamias | journal=Lynx, N. S. (Praha) | volume=44 | pages=27–138 }}{{cite book | author1=Armitage, K.B. | author2=Blumstein, D.T. | year=2002 | chapter=Body-mass diversity in marmots. Holarctic marmots as a factor of biodiversity | editor1=K.B. Armitage | editor2=V.Yu. Rumiantsev | title=Holarctic Marmots as a Factor of Biodiversity | publisher=ABF Publishing House | pages=22–32 }} Squirrels typically have slender bodies with long, bushy tails and large eyes. In general, their fur is soft and silky, though much thicker in some species than others. The coat color of squirrels is highly variable between—and often even within—species.[http://www.wildlifeonline.me.uk/squirrels.html Tree Squirrels], Wildlife Online, 23 November 2010.

In most squirrel species, the hind limbs are longer than the forelimbs, while all species have either four or five toes on each foot. The feet, which include an often poorly developed thumb, have soft pads on the undersidesMilton (1984) and versatile, sturdy claws for grasping and climbing.{{cite web|url=http://animals.howstuffworks.com/mammals/squirrel-info.htm|title=Rodents|date=22 April 2008|publisher=How Stuff Works|access-date=30 December 2016}} Tree squirrels, unlike most mammals, can descend a tree headfirst. They do so by rotating their ankles 180 degrees, enabling the hind feet to point backward and thus grip the tree bark from the opposite direction.{{cite book|last1=Thorington|first1=Richard W.|last2=Koprowski|first2=John L.|last3=Steele|first3=Michael A.|last4=Whatton|first4=James F.|year=2012|page=8|title=Squirrels of the World|publisher=Johns Hopkins University Press|isbn=978-1-4214-0469-1}}

As their large eyes indicate, squirrels have excellent vision, which is especially important for the tree-dwelling species. Many also have a good sense of touch, with vibrissae on their limbs as well as their heads.

The teeth of sciurids follow the typical rodent pattern, with large incisors (for gnawing) that grow throughout life, and cheek teeth (for grinding) that are set back behind a wide gap, or diastema. The typical dental formula for sciurids is {{DentalFormula|upper=1.0.1.3|lower=1.0.1.3}}.The Beginning of the Age of Mammals Kenneth D. Rose (2006) {{ISBN|978-0-801-88472-6}} p. 326

The purposes of squirrels' tails, to benefit the squirrel, include:{{Cite web|url=http://www.nutsaboutsquirrels.com/1695/why-do-squirrels-have-bushy-tails/|title=Why do squirrels have bushy tails? | Nuts About Squirrels}}

• To keep rain, wind, or cold off itself.
• To cool off when hot, by pumping more blood through its tail.
• As a counterbalance when jumping about in trees
• As a parachute when jumping.
• To signal with.

The hairs from squirrel tails are prized in fly fishing when tying fishing flies.{{Cite web |last=Genova |first=Cosmo |date=2022-01-11 |title=How to Preserve a Squirrel Pelt For Fly Tying |url=https://www.fieldandstream.com/fishing/preserve-squirrel-pelt-fly-tying/ |access-date=2024-06-01 |website=Field & Stream |language=en-US}} Squirrel hair is very fine, making it better for tying fishing flies.{{Cite book |last=Valla |first=Mike |url=https://books.google.com/books?id=0AVDDQAAQBAJ&dq=%22squirrel+tail%22+%22guard+hair%22&pg=PA45 |title=Tying and Fishing Bucktails and Other Hair Wings: Atlantic Salmon Flies to Steelhead Flies |date=2016-09-05 |publisher=Rowman & Littlefield |isbn=978-0-8117-6532-9 |language=en}}

When the squirrel sits upright, its tail folded up its back may stop predators looking from behind from seeing the characteristic shape of a small mammal.

Squirrels live in almost every habitat, from tropical rainforest to semiarid desert, avoiding only the high polar regions and the driest of deserts. They are predominantly herbivorous, subsisting on seeds and nuts, but many will eat insects and even small vertebrates.[http://www.squirrels.org/faq.html Squirrel Place] {{webarchive|url=https://web.archive.org/web/20101227025300/http://www.squirrels.org/faq.html |date=27 December 2010 }}. squirrels.org. Retrieved 14 December 2010.

Many juvenile squirrels die in the first year of life. Adult squirrels can have a lifespan of 5 to 10 years in the wild. Some can survive 10 to 20 years in captivity.{{cite book|last1=Thorington|first1=Richard W.|last2=Koprowski|first2=John L.|last3=Steele|first3=Michael A.|last4=Whatton|first4=James F.|year=2012|page=12|title=Squirrels of the World|publisher=Johns Hopkins University Press|isbn=978-1-4214-0469-1}} Premature death may occur when a nest falls from the tree, in which case the mother may abandon her young if their body temperature is not correct. Many such baby squirrels have been rescued and fostered by a professional wildlife rehabilitator until they could be safely returned to the wild,{{cite web|url=http://www.squirrel-rehab.org/|title=Squirrel Rehab|access-date=19 August 2017}} although the density of squirrel populations in many places and the constant care required by premature squirrels means that few rehabilitators are willing to spend their time doing this and such animals are routinely euthanized instead.

File:Squirrel enjoying in the sun.jpg|Squirrel in sunlight

File:Squirrel in Chandigarh.jpg|Squirrel in Chandigarh

File:Squirrel near Chandigarh.jpg|Squirrel near Chandigarh

File:Squirrel on mango tree.jpg|Squirrel on mango tree

File:Baby of squirrel.jpg]]

Squirrels mate either once or twice a year and, following a gestation period of three to six weeks, give birth to a number of offspring that varies by species. The young are altricial, being born naked, toothless, and blind. In most species of squirrel, the female alone looks after the young, which are weaned at six to ten weeks and become sexually mature by the end of their first year. In general, the ground-dwelling squirrel species are social, often living in well-developed colonies, while the tree-dwelling species are more solitary.

Ground squirrels and tree squirrels are usually either diurnal or crepuscular,{{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|url-status=dead|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}} while the flying squirrels tend to be nocturnal—except for lactating flying squirrels and their young, which have a period of diurnality during the summer.{{cite journal | last=Törmälä | first=Timo | author2=Vuorinen, Hannu | author3=Hokkanen, Heikki | year=1980 | title=Timing of circadian activity in the flying squirrel in central Finland | journal=Acta Theriologica | volume=25 | issue=32–42 | pages=461–474 | doi=10.4098/at.arch.80-42 | doi-access=free |issn = 0001-7051 }}

During hot periods, squirrels have been documented to sploot, or lay their stomachs down on cool surfaces.{{cite web|last=McNamee|first=Kai|url=https://www.npr.org/2023/06/29/1185092056/squirrels-splooting-heat-wave-climate-change|title=The heat is making squirrels 'sploot' — a goofy act that signals something serious|publisher=NPR|date=June 29, 2023|accessdate=August 8, 2023}}

Squirrels, like other rodents, employ species-specific strategies to store food, buffering against periods of scarcity.{{cite journal | last1=Andersson | first1=Malte | last2=Krebs | first2=John | title=On the evolution of hoarding behaviour | journal=Animal Behaviour | volume=26 | year=1978 | issn=0003-3472 | doi=10.1016/0003-3472(78)90137-9 | pages=707–711| s2cid=53154232 }} In temperate regions, squirrels commonly cache nuts beneath leaf litter, inside hollow trees, or underground.{{cite journal | last1=HADJ-CHIKH | first1=LEILA Z. | last2=STEELE | first2=MICHAEL A. | last3=SMALLWOOD | first3=PETER D. | title=Caching decisions by grey squirrels: a test of the handling time and perishability hypotheses | journal=Animal Behaviour | volume=52 | issue=5 | year=1996 | issn=0003-3472 | doi=10.1006/anbe.1996.0242 | pages=941–948| doi-access=free }} However, in subtropical and humid environments, traditional caching can lead to mold growth, decomposition, or premature germination.{{cite journal | last1=Xiao | first1=Zhishu | last2=Gao | first2=Xu | last3=Zhang | first3=Zhibin | title=The combined effects of seed perishability and seed size on hoarding decisions by Pére David's rock squirrels | journal=Behavioral Ecology and Sociobiology | volume=67 | issue=7 | date=2013-04-05 | issn=0340-5443 | doi=10.1007/s00265-013-1531-8 | pages=1067–1075| bibcode=2013BEcoS..67.1067X | s2cid=253815798 }} To counteract these challenges, some squirrels, particularly in subtropical zones, hang nuts or mushrooms on tree branches.{{cite journal | last1=Xiao | first1=Zhishu | last2=Gao | first2=Xu | last3=Zhang | first3=Zhibin | title=The combined effects of seed perishability and seed size on hoarding decisions by Pére David's rock squirrels | journal=Behavioral Ecology and Sociobiology | volume=67 | issue=7 | date=2013-04-05 | issn=0340-5443 | doi=10.1007/s00265-013-1531-8 | pages=1067–1075| bibcode=2013BEcoS..67.1067X | s2cid=253815798 }} This behavior, believed to minimize fungal infections and reduce the risk of food loss, also inadvertently aids certain trees, like Cyclobalanopsis, in expanding their range, with forgotten or dislodged nuts sprouting in new locations, influencing forest ecology.{{cite journal | last1=Xu | first1=Han | last2=Xia | first2=Lian | last3=Spence | first3=John R | last4=Lin | first4=Mingxian | last5=Lu | first5=Chunyang | last6=Li | first6=Yanpeng | last7=Chen | first7=Jie | last8=Luo | first8=Tushou | last9=Li | first9=Yide | last10=Fang | first10=Suqin | title=Flying squirrels use a mortise-tenon structure to fix nuts on understory twigs | journal=eLife | volume=12 | date=2023-06-13 | pages=e84967 | issn=2050-084X | doi=10.7554/elife.84967| pmid=37309191 | pmc=10328505 | doi-access=free }} Two species of flying squirrel, the particolored flying squirrel and Hainan flying squirrel aid such cacheing by carving grooves into the nuts to fix the nuts tightly between small intersecting twigs, akin to the mortise-tenon joint in carpentry.{{cite journal | last1=Xu | first1=Han | last2=Xia | first2=Lian | last3=Spence | first3=John R | last4=Lin | first4=Mingxian | last5=Lu | first5=Chunyang | last6=Li | first6=Yanpeng | last7=Chen | first7=Jie | last8=Luo | first8=Tushou | last9=Li | first9=Yide | last10=Fang | first10=Suqin | title=Flying squirrels use a mortise-tenon structure to fix nuts on understory twigs | journal=eLife | volume=12 | date=2023-06-13 | pages=e84967 | issn=2050-084X | doi=10.7554/elife.84967| pmid=37309191 | pmc=10328505 | doi-access=free }}

File:Squirrel, Manyara National Park, Tanzania (2010).jpg, Tanzania]]

File:Squirrel in Seurasaari autumn.JPG in the Seurasaari island in Helsinki, Finland. The tame red squirrels on that island have become accustomed to humans thanks to their long-term feeding.Merja Laavola: Eläinten elintasosairaudet näkyvät Seurasaaressa. Vartti Etelä-Helsinki, Sanoma Kaupunkilehdet, 2010. (in Finnish)]]

File:Squirrel eating pumpkin seeds.webm seeds.]]

Because squirrels cannot digest cellulose, they must rely on foods rich in protein, carbohydrates, and fats. In temperate regions, early spring is the hardest time of year for squirrels because the nuts they buried are beginning to sprout (and thus are no longer available to eat), while many of the usual food sources are not yet available. During these times, squirrels rely heavily on tree buds. Squirrels, being primarily herbivores, eat a wide variety of plants, as well as nuts, seeds, conifer cones, fruits, fungi, and green vegetation. Some squirrels, however, also consume meat, especially when faced with hunger.{{cite news |website=bbc.co.uk |access-date=13 July 2018 |url=http://news.bbc.co.uk/2/hi/4489792.stm |title=Russian squirrel pack 'kills dog' |date=1 December 2005}} Squirrels have been known to eat small birds, young snakes, and smaller rodents, as well as bird eggs and insects. Some tropical squirrel species have shifted almost entirely to a diet of insects.Richard W. Thorington, Katie Ferrell – [https://books.google.com/books?id=Y7cuEWCWpLMC&pg=PA75 Squirrels: the animal answer guide], JHU Press, 2006, {{ISBN|0-8018-8402-0}}, {{ISBN|978-0-8018-8402-3}}, p. 75.

Squirrels, like pigeons and other fauna, are synanthropes, in that they benefit and thrive from their interaction in human environments. This gradual process of successful interaction is called synurbanization, wherein squirrels lose their inherent fear of humans in an urban environment.{{cite journal |last1=Peiman |first1=Kathryn |title=Sublethal consequences of urban life for wild vertebrates |journal=Environmental Reviews |date=June 2016 |volume=24 |issue=4 |pages=416–425 |doi=10.1139/er-2016-0029|hdl=1807/74036 |hdl-access=free }} When squirrels were almost completely eradicated during the Industrial Revolution in New York, they were later re-introduced to "entertain and remind" humans of nature. The squirrel blended into the urban environment so efficiently that when synanthropic behavior stops (i.e. people do not leave trash outside during particularly cold winters), they can become aggressive in their search for food.

Aggression and predatory behavior has been observed in various species of ground squirrels, in particular the thirteen-lined ground squirrel.{{cite journal | last=Friggens | first=M. | title=Carnivory on Desert Cottontails by Texas Antelope Ground Squirrels | jstor=3672818 | journal=The Southwestern Naturalist | volume=47 | issue=1 | pages=132–133 | year=2002 | doi=10.2307/3672818| bibcode=2002SWNat..47..132F }} For example, Bernard Bailey, a scientist in the 1920s, observed a thirteen-lined ground squirrel preying upon a young chicken.{{cite journal | last=Bailey | first=B. | title=Meat-eating propensities of some rodents of Minnesota | journal=Journal of Mammalogy | volume=4 | issue= 2| page=129 | year=1923 | doi = 10.1093/jmammal/4.2.129 }} Wistrand reported seeing this same species eating a freshly killed snake.{{cite journal | last=Wistrand | first=E.H. | title=Predation on a Snake by Spermophilus tridecemlineatus | jstor=2424389 | journal=American Midland Naturalist | volume=88 | issue=2 | pages=511–512 | year=1972 | doi=10.2307/2424389}} There has also been at least one report of squirrels preying on atypical animals, such as an incident in 2005 where a pack of black squirrels killed and ate a large stray dog in Lazo, Russia.{{cite news |title=Russian Squirrel Pack Kills Dog |url=http://news.bbc.co.uk/2/hi/4489792.stm |website=BBC News |date=December 2005 |access-date=7 August 2020}} Squirrel attacks on humans are exceedingly rare, but do occur.{{cite news |title=Cornwall squirrel 'pack' attacks boy, three |work=BBC News |date=14 July 2016 |url=https://www.bbc.com/news/uk-england-cornwall-36792959 |access-date=7 August 2020}}{{cite web |last1=Lafrance |first1=Adrienne |title=When Squirrels Attack – A cautionary tale |url=https://www.theatlantic.com/science/archive/2017/06/when-squirrels-attack/531129/ |website=The Atlantic |date=21 June 2017 |access-date=7 August 2020}}

Whitaker examined the stomachs of 139 thirteen-lined ground squirrels and found bird flesh in four of the specimens and the remains of a short-tailed shrew in one;{{cite journal | last=Whitaker | first=J.O. | title=Food and external parasites of Spermophilus tridecemlineatus in Vigo County, Indiana | jstor=1379067 | journal=Journal of Mammalogy | volume=53 | issue=3 | pages=644–648 | year=1972 | doi=10.2307/1379067}} Bradley, examining the stomachs of white-tailed antelope squirrels, found at least 10% of his 609 specimens' stomachs contained some type of vertebrate, mostly lizards and rodents.{{cite journal | last=Bradley | first=W. G. | title=Food habits of the antelope ground squirrel in southern Nevada | jstor=1377723 | journal=Journal of Mammalogy | volume=49 | issue=1 | pages=14–21 | doi=10.2307/1377723 | year=1968}} Morgart observed a white-tailed antelope squirrel capturing and eating a silky pocket mouse.{{cite journal | last=Morgart | first=J. R. | title=Carnivorous behavior by a white-tailed antelope ground squirrel Ammospermophilus leucurus | jstor=3670745 | journal=The Southwestern Naturalist | volume=30 | issue=2 | pages=304–305 | doi=10.2307/3670745 |date=May 1985| bibcode=1985SWNat..30..304M }}

File:One squirrel open mouth.jpg (Sciurus niger) outside the Cleveland Museum of Art]]

File:Taiwanrisu-2009.ogv]]

File:Prevostova vjeverica u Zagrebu.2.jpg (Callosciurus prevostii) in Zagreb Zoo, Croatia]]

{{further|List of sciurids}}

The living squirrels are divided into five subfamilies, with about 58 genera and some 285 species.{{cite journal|author1=Wilson, D.E. |author2=Reeder, D.M. | title=Class Mammalia Linnaeus, 1758. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness | journal=Zootaxa| volume=3148| year=2011| pages=56–60|doi=10.11646/zootaxa.3148.1.9 | url=http://mapress.com/zootaxa/2011/f/zt03148p060.pdf}} The oldest squirrel fossil, Hesperopetes, dates back to the Chadronian (late Eocene, about 40–35 million years ago) and is similar to modern flying squirrels.{{Cite journal | last1 = Emry | first1 = R. J. | last2 = Korth | first2 = W. W. | title = A new genus of squirrel (Rodentia, Sciuridae) from the mid-Cenozoic of North America | journal = Journal of Vertebrate Paleontology | volume = 27 | issue = 3 | pages = 693–698 | year = 2007 | doi = 10.1671/0272-4634(2007)27[693:ANGOSR]2.0.CO;2 | s2cid = 85847849 }}

A variety of fossil squirrels, from the latest Eocene to the Miocene, have not been assigned with certainty to any living lineage. At least some of these probably were variants of the oldest basal "protosquirrels" (in the sense that they lacked the full range of living squirrels' autapomorphies). The distribution and diversity of such ancient and ancestral forms suggest the squirrels as a group may have originated in North America.Steppan & Hamm (2006)

Apart from these sometimes little-known fossil forms, the phylogeny of the living squirrels is fairly straightforward. The three main lineages are the Ratufinae (Oriental giant squirrels), Sciurillinae and all other subfamilies. The Ratufinae contain a mere handful of living species in tropical Asia. The neotropical pygmy squirrel of tropical South America is the sole living member of the Sciurillinae. The third lineage, by far the largest, has a near-cosmopolitan distribution. This further supports the hypothesis that the common ancestor of all squirrels, living and fossil, lived in North America, as these three most ancient lineages seem to have radiated from there; if squirrels had originated in Eurasia, for example, one would expect quite ancient lineages in Africa, but African squirrels seem to be of more recent origin.

The main group of squirrels can be split into five subfamilies: the Callosciurinae, 60 species mostly found in South East Asia; the Ratufinae, 4 cat-sized species found in south and southeast Asia; the Sciurinae, which contains the flying squirrels (Pteromyini) and the tree squirrels, 83 species found worldwide;Steppan, S. J. B. L. Storz, and R. S. Hoffmann. 2004. [http://www.bio.fsu.edu/~steppan/Steppan_et_al_Sciuridae.pdf Nuclear DNA phylogeny of the squirrels (Mammalia: Rodentia) and the evolution of arboreality from c-myc and RAG1]. Molecular Phylogenetics and Evolution, 30:703-719. Sciurillinae, a single South American species; and Xerinae, which includes three tribes of mostly terrestrial squirrels, including the Marmotini (marmots, chipmunks, prairie dogs, and other Holarctic ground squirrels), Xerini (African and some Eurasian ground squirrels), and Protoxerini (African tree squirrels).

• Basal and incertae sedis Sciuridae (all fossil)
• Hesperopetes
• Kherem
• Lagrivea
• Oligosciurus
• Plesiosciurus
• Prospermophilus
• Sciurion
• Similisciurus
• Sinotamias
• Vulcanisciurus
• Subfamily Cedromurinae (fossil)
• Subfamily Ratufinae – Oriental giant squirrels (1 genus, 4 species)
• Subfamily Sciurillinae – neotropical pygmy squirrel (monotypic)
• Subfamily Sciurinae
• Tribe Sciurini – tree squirrels (5 genera, about 38 species)
• Tribe Pteromyini – true flying squirrels (15 genera, about 45 species)
• Subfamily Callosciurinae – Asian ornate squirrels
• Tribe Callosciurini (13 genera, nearly 60 species)
• Tribe Funambulini palm squirrels (1 genus, 5 species)
• Subfamily Xerinae – terrestrial squirrels
• Tribe Xerini – spiny squirrels (3 genera, 6 species)
• Tribe Protoxerini (6 genera, about 50 species)
• Tribe Marmotini – ground squirrels, marmots, chipmunks, prairie dogs, etc. (6 genera, about 90 species)

{{cladogram|align=left|clades={{Clade|style=width:24em;

|label1=Sciuridae{{cite journal |last=Sheets |first=A. D. |last2=Chavez |first2=A. S. |title=Evolution of Pelage Luminance in Squirrels (Sciuridae) |journal=Frontiers in Ecology and Evolution |volume=8 |date=2020 |issue=249 |doi=10.3389/fevo.2020.00249 |doi-access=free}}

{{cite journal |last=Hawkins |first=M. T. R. |last2=Leonard |first2=J. A. |last3=Helgen |first3=K. M. |last4=McDonough |first4=M. M. |last5=Rockwood |first5=L. L. |last6=Maldonado |first6=J. E. |title=Evolutionary history of endemic Sulawesi squirrels constructed from UCEs and mitogenomes sequenced from museum specimens |journal=BMC Evolutionary Biology |volume=16 |issue=1 |date=2016 |doi=10.1186/s12862-016-0650-z |doi-access=free|hdl=10261/132111 |hdl-access=free }}

{{cite journal |last=Arbogast |first=B. S. |title=A Brief History of the New World Flying Squirrels: Phylogeny, Biogeography, and Conservation Genetics |journal=Journal of Mammalogy |volume=88 |issue=4 |date=2007 |doi=10.1644/06-mamm-s-322r1.1 |doi-access=free |pages=840–849}}

{{cite journal |last=Helgen |first=K. M. |last2=Cole |first2=F. R. |last3=Helgen |first3=L. E. |last4=Wilson |first4=D. E. |title=Generic Revision in the Holarctic Ground Squirrel Genus Spermophilus |journal=Journal of Mammalogy |volume=90 |issue=2 |date=2009 |doi=10.1644/07-mamm-a-309.1 |doi-access=free |pages=270–305}}

|1={{clade

|1={{clade

|1={{clade

|1={{clade

|label1=Sciurinae  

|1={{clade

|label1=Pteromyini  

|1={{clade

|1={{clade

|1=Eoglaucomys

|2={{clade

|1=Glaucomys

|2={{clade

|1=Iomys

|2={{clade

|1=Hylopetes

|2=Petaurillus

|3=Petinomys

}}

}}

}}

}}

|2={{clade

|1=Petaurista

|2={{clade

|1={{clade

|1=Pteromys

|2={{clade

|1=Aeromys

|2=Biswamoyopterus

|3=Eupetaurus

}}

}}

|2={{clade

|1=Pteromyscus

|2={{clade

|1=Belomys

|2={{clade

|1=Aeretes

|2=Trogopterus

}}

}}

}}

}}

}}

}}

|label2=Sciurini  

|2={{clade

|1=Tamiasciurus

|2={{clade

|1=Rheithrosciurus

|2={{clade

|1=Sciurus

|2=Microsciurus

|3=Syntheosciurus

}}

}}

}}

}}

}}

|2={{clade

|label1=Callosciurinae  

|1={{clade

|label1=Callosciurini  

|1={{clade

|1=Exilisciurus

|2={{clade

|1=Menetes

|2=Rhinosciurus

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|3={{clade

|1=Callosciurus

|2={{clade

|1=Nannosciurus

|2={{clade

|1=Lariscus

|2=Sundasciurus

}}

}}

}}

|4={{clade

|1=Hyosciurus

|2={{clade

|1=Prosciurillus

|2=Rubrisciurus

}}

}}

|5={{clade

|1=Dremomys

|2=Glyphotes

|3=Tamiops

}}

}}

|label2=Funambulini  

|2=Funambulus

}}

|label2=Xerinae  

|2={{clade

|1={{clade

|label1=Xerini  

|1={{clade

|1=Spermophilopsis

|2={{clade

|1=Atlantoxerus

|2=Xerus

}}

}}

}}

|2={{clade

|label1=Marmotini  

|1={{clade

|1={{clade

|1=Sciurotamias

|2={{clade

|1=Eutamias

|2=Neotamias

|3=Tamias

}}

}}

|2={{clade

|1={{clade

|1=Ammospermophilus

|2=Notocitellus

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|2={{clade

|1={{clade

|1=Callospermophilus

|2=Otospermophilus

}}

|2={{clade

|1=Marmota

|2={{clade

|1=Spermophilus

|2={{clade

|1=Urocitellus

|2={{clade

|1=Ictidomys

|2={{clade

|1=Poliocitellus

|2={{clade

|1=Cynomys

|2=Xerospermophilus

}}

}}

}}

}}

}}

}}

}}

}}

}}

|label2=Protoxerini  

|2={{clade

|1=Heliosciurus

|2={{clade

|1=Epixerus

|2=Funisciurus

|3=Myosciurus

|4=Paraxerus

|5=Protoxerus

}}

}}

}}

}}

}}

}}

|2={{clade

|label1=Sciurillinae  

|1=Sciurillus

}}

}}

|2={{clade

|label1=Ratufinae  

|1=Ratufa

}}

}}

}}}}

{{clear}}

{{main|Tree squirrel#Relationship with humans}}

{{Portal|Mammals}}

• List of animal names#squirrel
• Variant Creutzfeldt–Jakob disease (Kuru) from eating squirrel brains.{{cite news |last1=Blakeslee |first1=Sandra |title=Kentucky Doctors Warn Against a Regional Dish: Squirrels' Brains |url=https://www.nytimes.com/1997/08/29/us/kentucky-doctors-warn-against-a-regional-dish-squirrels-brains.html |access-date=18 April 2019 |newspaper=The New York Times |date=29 August 1997}}{{cite web |url=https://www.livescience.com/63831-squirrel-brains-rare-disorder-creutzfeldt-jakob-disease.html |title=Man Dies from Extremely Rare Disease After Eating Squirrel Brains |first1=Rachael |last1=Rettner |date=October 15, 2018 |publisher=LiveScience |accessdate=April 9, 2022}}

{{Anchor|Notes|reason="Notes" is the old section name, which was changed to "References" on 6 June 2018}}

{{Reflist|30em}}

{{Anchor|References|reason="References" is the old section name, which was changed to "Further reading" on 6 June 2018}}

• {{cite book| last1 = Whitaker | first1= John O. Jr. |last2= Elman|first2=Robert|date=1980|title=The Audubon Society Field Guide to North American Mammals|edition=2nd|publisher=Alfred A. Knopf, Jr.| location = New York|isbn=0-394-50762-2}}

• Milton, Katherine (1984): "Family Sciuridae". In: Macdonald, D. (ed.): The Encyclopedia of Mammals: 612–623. Facts on File, New York. {{ISBN|0-87196-871-1}}.
• Steppan, Scott J. and Hamm, Shawn M. (2006): Tree of Life Web Project – [http://tolweb.org/Sciuridae/16456/2006.05.13 "Sciuridae (Squirrels)"]. Version of 13 May 2006. Retrieved 10 December 2007.
• {{Cite journal | last1 = Steppan | first1 = S. J. | last2 = Storz | first2 = B. L. | last3 = Hoffmann | first3 = R. S. | doi = 10.1016/S1055-7903(03)00204-5 | title = Nuclear DNA phylogeny of the squirrels (Mammalia: Rodentia) and the evolution of arboreality from c-myc and RAG1 | journal = Molecular Phylogenetics and Evolution | volume = 30 | issue = 3 | pages = 703–719 | year = 2004 | pmid = 15012949| bibcode = 2004MolPE..30..703S }}
• Thorington, R.W. and Hoffmann, R.S. (2005): "Family Sciuridae". In: Mammal Species of the World: A Taxonomic and Geographic Reference: 754–818. Johns Hopkins University Press, Baltimore.

{{Commons|Sciuridae}}

{{Wikispecies|Sciuridae}}

{{Wiktionary|squirrel}}

• {{wikiquote-inline}}
• [http://tolweb.org/Sciuridae/16456 Tree of Life: Sciuridae]
• [http://northernbushcraft.com/animalTracks/squirrel/notes.htm Squirrel Tracks]: How to identify squirrel tracks in the wild
• [https://web.archive.org/web/20070614105921/http://animals.nationalgeographic.com/animals/mammals/squirrel.html National Geographic link on Squirrels]
• [https://web.archive.org/web/20131206211135/http://squirrels.org/names.html List of names of squirrel taxa]

{{Rodents}}

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{{S. Callosciurinae nav}}

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Category:Sciuromorpha

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Category:Extant Eocene first appearances

Category:Rodents by common name

Category:Taxa named by Gotthelf Fischer von Waldheim