Sciurus carolinensis, Gmelin, 1788
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publication ID |
https://doi.org/ 10.5281/zenodo.6840226 |
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DOI |
https://doi.org/10.5281/zenodo.6818756 |
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persistent identifier |
https://treatment.plazi.org/id/064D0660-FFEF-ED13-FA6E-FA09FBABFA91 |
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treatment provided by |
Diego |
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scientific name |
Sciurus carolinensis |
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Eastern Gray Squirrel
Sciurus carolinensis View in CoL
French: Ecureuil gris / German: Ostliches Grauhdrnchen / Spanish: Ardilla gris oriental
Other common names: Gray Squirrel
Taxonomy. Sciurus carolinensis Gmelin, 1788 View in CoL ,
“Carolina.”
Five subspecies are recognized.
Subspecies and Distribution.
S.c.extimusBangs,1896—extremeSFlorida(USA).
S.c.fuliginosusBachman,1839—SLouisiana,SMississippi,andSAlabama(USA).
S. c. pennsylvanicus Ord, 1815 — C & NE USA from E Nebraska and NE Kansas to the S and E Great Lakes states and extending S through the Appalachian Mts, also in SE Canada, in SE Ontario and S Quebec. Subspecies pennsylvanicus is the most likely to have been introduced into Great Britain, Ireland, Italy, South Africa, Australia, México, and various localities in Canada, Hawaii, and W continental USA. Introductions to Australia, Hawaii, and perhaps México have failed.
Descriptive notes. Head-body 200-315 mm,tail 150-250 mm; weight 300-710 g. The Eastern Gray Squirrel has grizzled pale to slate-gray dorsal pelage that can be washed with cinnamon, especially on haunches and cheeks. White-to-cream eye ring is usually conspicuous. White-to-buff postauricular patches are especially visible in winter. Venter is white, buff, or cinnamon. Tail retains color of dorsum, grizzled with faintly visible black longitudinal lines and sometimes washed with brown and frosted with white or cream. Melanism occurs especially in northern populations, where an energetic advantage occurs in winter. White and albino populations are known. Nominate carolinensis is moderately sized and has typical color. Subspecies extimus is the smallest and darkest. Subspecies fuliginosus has rich dark colors and venter is often cinnamon. Subspecies hypophaeus is the largest and often has increased encroachment of dorsal color on venter. Subspecies pennsylvanicus is large and lacks encroachment of dorsal color on venter. Chromosomal complement is 2n = 40 and FN = 76.
Habitat. Deciduous hardwood or mixed forests, especially with high diversity of mature trees. Where introduced, the Eastern Gray Squirrel appears to retain similar habitat preferences but does appear to use coniferous areas more than in its natural distribution. They are a common synanthrope found in many urban and suburban areas, even when trees are somewhat sparse.
Food and Feeding. The Eastern Gray Squirrel is herbivorous but will opportunistically feed on a diversity of foods. Tree seeds and nuts are most important in diets, but fruits, buds, flowers, herbs, bark, phloem, and sap are eaten. Hypogeous and epigeous fungi can be an important seasonal foods. The Eastern Gray Squirrel will opportunistically feed on animal matter including insects, larvae, bird eggs, avian nestlings, bones, and scavenged carcasses; cannibalism has been observed. A conspicuous behavior is the
autumnal scatterhoarding of seeds, nuts, and acorns of low perishability for winter food. Seeds are collected at the parent tree, dispersed to distant sites, and buried. Scatterhoarding below ground reduces loss to seed competitors that rely on sight to locate seeds,typically birds, and likely decrease profitability of pilferage by mammals. To preventloss to seed germination after caching, white oak acorns (subgenus Lepidobalanus), the Eastern Gray Squirrel excises seed embryos to ensure that nutrients remain available until recovered and eaten. Caches are recovered in winter and spring with spatial memory and olfactory cues.
Breeding. Although mating can occur in November—July, local populations typically have two annual seasons in December—February and May-June. Males follow female reproductive condition by approaching and sniffing their genitalia in the days and weeks before estrus. Males congregate at the nest of a female at sunrise on the morning of her estrus. On her single day of estrus each breeding season, as many as 34 males will pursue a female during her mating bout and emit a snort or wheeze as a call during the chase. Dominant males pursue and mate with the female; low-ranking males copulate by waiting on the periphery of the mating chase in the event that the female evades aggression of dominant males. Evasive females will emit high-pitched whines that are similar to alarm calls if males are unable to relocate her. Copulation lasts less than 30 seconds after which a copulatory plug forms within the female from the coagulation of semen. Females will remove and consume the plugs and mate with multiple males. After a gestation of 44 days, litters averaging 2-8 young are born in leaf nests or tree cavities. Some females produce two litters in a year, although thisis uncommon except in the most mild and food-laden years. Litter size and prevalence of lactation decrease in poor food years and complete failures have been reported. Young emerge from the nest after 7-8 weeks and are weaned by c.10 weeks old. Adult size is usually reached by 8-9 months of age. Although a rare female may breed as early as 5-5 months of age, most do not reproduce until at least their yearling year. All males disperse from their natal areas soon after weaning; however, some females are philopatric and remain in their natal area to form matrilines.
Activity patterns. Eastern Gray Squirrels are diurnal and active throughout the year. Activity is distinctly bimodal in summer with early morning and late afternoon-early evening peaks in activity and midday lull. Winter activity is unimodal and focused during relative warmth of midday. During periods of extreme inclement weather, Eastern Gray Squirrels can enter short periods of torpor in a nest. Wind and rain result in reduced activity outside of the nest.
Movements, Home range and Social organization. The Eastern Gray Squirrel dens in cavities within trees and often constructs spherical dreys of leaves, pine needles, and twigs; individuals use 5-10 nests over the course of a year. The Eastern Gray Squirrel is among the most social of the tree squirrels and forms kin clusters in forests through retention of female offspring in or near their natal areas. Groups of related females nest together at night; unrelated males and females are rarely permitted to join such nesting assemblages. Agonistic behaviors, primarily chases and brief combat, are directed almost exclusively toward unrelated individuals, whereas amicable behaviors such as greeting and grooming are only shared with closely related females. Unrelated males will also nest together, particularly in winter, although these assemblages are ephemeral in composition. Physical combat most often involves swatting and biting of the haunches, ears, and tail. Cheek glands are used to scent-mark trees, and these glands are smelled when individuals meet. Traditional scent-marking sites are found in protected areas, such as under low branches or on undersides of slanted tree trunks. Males gnaw bark at the location and wipe their cheeks back and forth to deposit scent, sometimes urinating. Home ranges overlap considerably; females with young may defend exclusive-use core areas, and adult females and their relatives are important in regulating settlement through agonistic behavior. Home ranges are 0-5-20-6 ha, larger for males, and decrease with habitat fragment size. Alarm calls are series of medium pitched barks, often followed by long high-pitched whines dependent on level of disturbance. Tail flicking also appears to provide a visual indicator of alarm. Historically, the Eastern Gray Squirrel was known to migrate en masse in the millions, primarily in autumn and in apparent response to tree seed crop failure. Immense size of these movements prompted early naturalists J. J. Audubon and J. Bachman to use the synonym Sciurus migratorius. Such movements have been rarely reported in the last 100 years and always are more regional and less grandiose.
Status and Conservation. Classified as Least Concern on The IUCN Red List. Population trend of the Eastern Gray Squirrelsis Stable. They are frequently valued in parks and cities and are also hunted as game animals in their native distribution. The Eastern Gray Squirrel can be a pest in orchards, gardens, agricultural fields, and forest plots and at bird feeder. It has been labeled as one of the world’s 100 worst invasive species. Introductions to the United Kingdom, Ireland, and Italy have resulted in the continued spread with deleterious consequences that include stripping of bark and subsequent tree mortality, spread of disease such as poxviruses, and rapid displacement of the native Eurasian Red Squirrel (S. vulgaris). In Washington in the western USA, introductions of the Eastern Gray Squirrel are believed to play a role in the reduction of the imperiled Western Gray Squirrel (S. griseus) and may be also be doing so in Oregon and California. Habitat loss and fragmentation remain the most significant threats to the Eastern Gray Squirrel in their native distribution, but populations are currently healthy.
Bibliography. Bertolino (2009), Bertolino et al. (2014), Goldstein et al. (2015, 2016), Gonzales (2005), Gurnell (1987), Gurnell, Rushton et al. (2006), Gurnell, Wauters, Lurz & Tosi (2004), Gurnell, Wauters, Preatoni & Tosi (2001), Hopewell & Leaver (2008), Hopewell et al. (2008), Kenward (1989), Kenward & Parish (1986), Koprowski (19933, 1993c, 1993d, 1994a, 1996, 2005a), Lurz et al. (2001), Martinoli et al. (2010), Romeo et al. (2015), Signorile & Evans (2007), Steele & Koprowski (2001), Steele, Manierre et al. (2006), Thorington et al. (2012), Wauters, Gurnell et al. (2001, 2002), Wauters, Lurz & Gurnell (2000), Wauters, Tosi & Gurnell (2002).
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