Squirrel

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This article is about the squirrel family (Sciuridae) as a whole. For other uses, see Squirrel (disambiguation).

Squirrels
Temporal range: Late Eocene – Recent
Various members of the family Sciuridae
Urocitellus columbianus
 Paraxerus cepapi
Geosciurus inauris Marmota sp. Cynomys ludovicianus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Suborder: Sciuromorpha
Family: Sciuridae
Fischer de Waldheim
, 1817
Type genus
Sciurus
Linnaeus, 1758
Subfamilies and tribes

Squirrels are members of the family Sciuridae (/sɪˈjuːrɪdeɪ, -diː/), a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia.[1] The earliest known fossilized squirrels date from the Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and to the dormice.[citation needed]

Etymology

The word squirrel, first attested in 1327, comes from the

Latin word sciurus, which was taken from the Ancient Greek word σκίουρος (skiouros; from σκία-ουρος) 'shadow-tailed', referring to the long bushy tail which many of its members have.[2][3]

The native

Common Germanic origin, cognates of which are still used in other Germanic languages, including the German Eichhörnchen (diminutive of Eichhorn, which is not as frequently used); the Norwegian ikorn/ekorn; the Dutch eekhoorn; the Swedish ekorre and the Danish
egern.

A group of squirrels is called a "dray"[5] or a "scurry".[6]

Characteristics

Reaching out for food on a garden bird feeder, this squirrel can rotate its hind feet, allowing it to descend a tree head-first.
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 10–14 cm (3.9–5.5 in) in total length and just 12–26 g (0.42–0.92 oz) in weight,[7][8] to the Bhutan giant flying squirrel at up to 1.27 m (4 ft 2 in) in total length,[9] and several marmot species, which can weigh 8 kg (18 lb) or more.[10][11] Squirrels typically have slender bodies with very long very 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.[12]

In most squirrel species, the hind limbs are longer than the fore limbs, while all species have either four or five toes on each foot. The feet, which include an often poorly developed

Tree squirrels, unlike most mammals, can descend a tree head-first. 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.[15]

Squirrels live in almost every habitat, from tropical

insects and even small vertebrates.[16]

As their large eyes indicate, squirrels have an excellent sense of 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.[13]

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 1.0.1.31.0.1.3.[17]

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.

wildlife rehabilitator until they could be safely returned to the wild,[19] 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.

Stated purposes of squirrels' tails, to benefit the squirrel, include:[20]

  • 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

undercoat.[citation needed
]

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.

  • Squirrel in sunlight

    Squirrel in sunlight

  • Squirrel in Chandigarh

    Squirrel in Chandigarh

  • Squirrel near Chandigarh

    Squirrel near Chandigarh

  • Squirrel on mango tree

    Squirrel on

    mango tree

Behavior

Young squirrels

Squirrels mate either once or twice a year and, following a

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.[13]

Ground squirrels and tree squirrels are usually either

crepuscular,[21] 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.[22]

During hot periods, squirrels have been documented to sploot, or lay their stomachs down on cool surfaces.[23]

Squirrels, like other rodents, employ species-specific strategies to store food, buffering against periods of scarcity.

Cyclobalanopsis, in expanding their range, with forgotten or dislodged nuts can sprout in new locations, influencing forest ecology.[27] Two species of flying squrrirel, 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[27]

Feeding

Manyara National Park, Tanzania
Red squirrel 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.[28]

Because squirrels cannot digest

tropical squirrel species have shifted almost entirely to a diet of insects.[30]

Squirrels, like

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.[31] 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.[32] For example, Bernard Bailey, a scientist in the 1920s, observed a thirteen-lined ground squirrel preying upon a young chicken.[33] Wistrand reported seeing this same species eating a freshly killed snake.[34] 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.[35] Squirrel attacks on humans are exceedingly rare, but do occur.[36][37]

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

silky pocket mouse.[40]

Taxonomy

Squirrel (Sciurus niger) outside the Cleveland Museum of Art
A squirrel (Callosciurus erythraeus thaiwanensis) in Japan
Prevost's Squirrel (Callosciurus prevostii) in Zagreb Zoo, Croatia

The living squirrels are divided into five

million years ago) and is similar to modern flying squirrels.[42]

A variety of fossil squirrels, from the latest

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.[43]

Apart from these sometimes little-known fossil forms, 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.[43]

The main group of squirrels can be split into five subfamilies. The

Holarctic ground squirrels), Xerini (African and some Eurasian ground squirrels), and Protoxerini
(African tree squirrels).

Taxonomy list

Society

Squirrels have been kept as pets in Western society at least until the 19th century. Because of their small size and tame nature, they were especially popular with women and the clergy.[45]

Depiction of a pet squirrel on a leash with a feeder in a medieval antiphonary (Bruges, Public Library, MS. SVC 010A)

Squirrels are a cause for concern because they often cause electrical disruptions. It has been hypothesized that the threat to the internet, infrastructure and services posed by squirrels may exceed that posed by cyber-attacks.[46]

Squirrels have been reported to be "successfully trained" in

illicit drugs and in 2023, a team of six Eurasian red squirrels had become part of a sub-unit within the Chongqing city police dog brigade. According to Chongqing police department, their small size and agility are beneficial as they are able to help the police detect drugs through "tiny spaces" in warehouses and storage units that dogs are unable to reach. Yin Jin, a police dog handler, who had been assigned to train these squirrels told The Paper that "these squirrels have an acute sense of smell. But in the past, our training problems for small rodents was not developed enough to attempt a program like this" and that her team of squirrels have so far done an "excellent job" in drug detection exercises, but are not yet ready to be deployed.[47][48][49]

See also

References

  1. ^ Seebeck, J. H. "Sciuridae" (PDF). Fauna of Australia. Archived from the original (PDF) on 17 January 2015. Retrieved 24 November 2013.
  2. The Oxford English Dictionary
    (2nd. ed.). Oxford University Press. 1989. Retrieved 8 November 2010.
  3. ^ Whitaker & Elman (1980): 370
  4. ^ "Squirrel". Online Etymology Dictionary. Retrieved 7 February 2008.
  5. ISBN 978-0-670-30044-0
    .
  6. ^ Universe in Your Pocket by Joel Levy, published by Barnes & Noble, Inc.
  7. ISBN 0-12-408355-2
    .
  8. ISBN 967-99947-1-6
    .
  9. ^ Choudhury, A. (2002). "Petaurista nobilis singhei: First record in India and a note on its taxonomy". The Journal of the Bombay Natural History Society. 99 (1): 30–34.
  10. ^ Kryštufek, B.; B. Vohralík (2013). "Taxonomic revision of the Palaearctic rodents (Rodentia). Part 2. Sciuridae: Urocitellus, Marmota and Sciurotamias". Lynx, N. S. (Praha). 44: 27–138.
  11. ^ Armitage, K.B.; Blumstein, D.T. (2002). "Body-mass diversity in marmots. Holarctic marmots as a factor of biodiversity". In K.B. Armitage; V.Yu. Rumiantsev (eds.). Holarctic Marmots as a Factor of Biodiversity. ABF Publishing House. pp. 22–32.
  12. ^ Tree Squirrels, Wildlife Online, 23 November 2010.
  13. ^ a b c Milton (1984)
  14. ^ "Rodents". How Stuff Works. 22 April 2008. Retrieved 30 December 2016.
  15. ISBN 978-1421404691
    .
  16. ^ a b Squirrel Place Archived 27 December 2010 at the Wayback Machine. squirrels.org. Retrieved 14 December 2010.
  17. ISBN 978-0-801-88472-6
    p. 326
  18. ISBN 978-1421404691
    .
  19. ^ "Squirrel Rehab". Retrieved 19 August 2017.
  20. ^ "Why do squirrels have bushy tails? | Nuts About Squirrels".
  21. ^ "Red & Gray Squirrels in Massachusetts". MassWildlife. Massachusetts Division of Fisheries and Wildlife. Archived from the original on 17 May 2013. Retrieved 3 April 2012.
  22. doi:10.4098/at.arch.80-42
    .
  23. ^ McNamee, Kai (29 June 2023). "The heat is making squirrels 'sploot' — a goofy act that signals something serious". NPR. Retrieved 8 August 2023.
  24. ISSN 0003-3472
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  25. ISSN 0003-3472
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  26. ^
    ISSN 0340-5443
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  27. ^
    PMC 10328505
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  28. ^ Merja Laavola: Eläinten elintasosairaudet näkyvät Seurasaaressa. Vartti Etelä-Helsinki, Sanoma Kaupunkilehdet, 2010. (in Finnish)
  29. bbc.co.uk
    . 1 December 2005. Retrieved 13 July 2018.
  30. ISBN 978-0-8018-8402-3
    , p. 75.
  31. hdl:1807/74036
    .
  32. JSTOR 3672818
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  33. doi:10.1093/jmammal/4.2.129
    .
  34. JSTOR 2424389
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  35. ^ "Russian Squirrel Pack Kills Dog". BBC News. December 2005. Retrieved 7 August 2020.
  36. ^ "Cornwall squirrel 'pack' attacks boy, three". BBC News. 14 July 2016. Retrieved 7 August 2020.
  37. ^ Lafrance, Adrienne (21 June 2017). "When Squirrels Attack - A cautionary tale". The Atlantic. Retrieved 7 August 2020.
  38. JSTOR 1379067
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  39. JSTOR 1377723
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  40. JSTOR 3670745
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  41. doi:10.11646/zootaxa.3148.1.9
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  42. S2CID 85847849
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  43. ^ a b Steppan & Hamm (2006)
  44. ^ Steppan, S. J. B. L. Storz, and R. S. Hoffmann. 2004. 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.
  45. ^ Kathleen Walker-Meikle, Medieval Pets, Woodbridge: The Boydell Press, 2012, p. 14 et passim
  46. ^ Goud, Naveen (18 January 2017). "Squirrels cause more financial damage to critical Infrastructure than Cyber Attacks". Cybersecurity Insiders. Retrieved 23 July 2019.
  47. ^ "Drug-sniffing squirrels join China's police force". The Independent. 10 February 2023. Retrieved 3 March 2023.
  48. ^ Teh, Cheryl. "A squad of 6 drug-sniffing squirrels is China's latest line of defense against drugs". Insider. Retrieved 3 March 2023.
  49. ^ "How squirrels are China's newest weapons against drugs". Firstpost. 13 February 2023. Retrieved 3 March 2023.
  50. ^ Blakeslee, Sandra (29 August 1997). "Kentucky Doctors Warn Against a Regional Dish: Squirrels' Brains". The New York Times. Retrieved 18 April 2019.
  51. LiveScience
    . Retrieved 9 April 2022.

Further reading

External links

Wikimedia Commons has media related to Sciuridae.
Wikispecies has information related to Sciuridae.
Look up squirrel in Wiktionary, the free dictionary.
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