Sciurus griseus Ord 1818
Creators: name: Wilson, Don E.
name: Thomas E. Lacher, Jr
name: Mittermeier, Russell A.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Sciuridae
Sciurus
Sciurus griseus

description: 81. Western Gray Squirrel <i>Sciurus griseus</i> <b>French:</b> Ecureuil de Californie / <b>German:</b> Westliches Grauhérnchen / <b>Spanish:</b> Ardilla gris occidental <b>Other common names:</b> Silver Gray Squirrel <b>Taxonomy.</b> Sciurus griseus Ord, 1818, “The Dalles of the Columbia [River],” Wasco Co., Oregon, USA. Three subspecies are recognized. <b>Subspecies and Distribution.</b> S.g.griseusOrd,1818—WUSA,inWashington,Oregon,NCalifornia,andmostoftheSierraNevadaMtsinECalifornia. S.g.anthonyiMearns,1897—extremeSCalifornia(USA)toCBajaCalifornia(Mexico). S. g. migripes W. Bryant, 1889 — coastal ranges in California (USA), from San Francisco Bay S to near Los Angeles. <b>Descriptive notes.</b> Head-body 265-323 mm, tail 240-309 mm; weight 520-942 g. The Western Gray Squirrel has slate to silvergray dorsal pelage finely grizzled with black. Ears are steel or silver-gray and quite prominent, nearly double their relative length in many other squirrels; eye ring is buff to white. Venteris white, occasionally with wash of buff. Tail is colored similarly to dorsum, with slightly darker core and frosting of white to silver-gray. Nominate griseus is silvery gray on dorsum and limbs. Subspecies nigripesis much darker on dorsum and feet, approaching slate-gray in many individuals. Subspecies anthony: is intermediate in color. Chromosomal complementis 2n = 40 and FN = 76 <b>Habitat.</b> Oak-conifer woodlands and mixed conifer forests on the mesic western side of the Pacific Coast Range. Xeric eastern slopes harbor the Western Gray Squirrel in open pine (Pinus, Pinaceae) forests. The Western Gray Squirrel is also found in cities and, occasionally, in nut orchards, but it does not generally thrive in close proximity to human developments. <b>Food and Feeding.</b> The Western Gray Squirrel forages on the ground during all seasons, with less use of the canopy than most tree squirrels. It is primarily herbivorous, feeding on seeds of oaks (Quercus, Fagaceae) and a variety of conifers. Epigeous and hypogeous fungi are also important foods and compose the majority of diets at some sites. Western Gray Squirrels feed on flowers, fruits, forbs, sap, and cambium and eat insects and bird eggs if encountered. They will feed heavily on commercial nut crops. <b>Breeding.</b> The Western Gray Squirrel can breed in December—July when up to seven males pursue a female on her single day of estrus. Aggression among males is considerable, and females will mate with multiple males. Litters of 1-6 young are born in nest cavities or leaf nests after 44-45 days of gestation; cavities appear to be preferred for rearing offspring. Most young leave the nest by May, and all disperse from their natal area. Sexual maturity is achieved at 10-11 months of age. <b>Activity patterns.</b> Western Gray Squirrels are diurnal and active throughout the year. Activity begins early in morning in summer and is distributed in bimodal fashion with lull during midday heat; winter activity is unimodal and focused around midday. <b>Movements, Home range and Social organization.</b> The Western Gray Squirrel constructs spherical drey nests of leaves, grasses, pine needles, and twigs. When in the canopy, this large-bodied squirrel appearsless agile and rarely leaps between branches, as do other tree squirrels. Adult individuals are solitary and are not territorial. Home ranges are less than 5 ha for both sexes in some park lands but expand to more than 73 ha for males and 22 ha for females elsewhere, with considerable overlap between individuals. Male home ranges overlap with many females, especially during the breeding season. Nests are in large trees in reasonably dense and diverse forest sites. When disturbed or threatened, the Western Gray Squirrel ascends a tree and faces the threat from an elevated perch while flagging its tail and projecting an alarm call in a series of moderately pitched chucks, which often increase in duration as the series progresses. <b>Status and Conservation.</b> Classified as Least Concern on The IUCN Red List. Population trend of the Western Gray Squirrel is unknown. The Western Gray Squirrelis listed as a threatened species in Washington and as sensitive in Oregon, USA. Lack of information on ecology, natural history, or threats likely impedes conservation and management efforts; it might be vulnerable to deforestation. This large-bodied squirrel is hunted for food and sport, and it is sometimes considered a pest in nut orchards. Introduced Eastern Gray Squirrels (S. carolinensis) and Eastern Fox Squirrels (S. niger) appear to be displacing Western Gray Squirrels in many parts ofits distribution. <b>Bibliography.</b> Bayrakci et al. (2001), Carraway &amp; Verts (1994), Cooper &amp; Muchlinski (2015), Garrison et al. (2005), Gregory et al. (2010), Linders et al. (2004), Mellink &amp; Contreras (1993), Ryan &amp; Carey (1995), Thorington etal. (2012).
description: Published as part of <i>Don E. Wilson, Thomas E. Lacher, Jr &amp; Russell A. Mittermeier, 2016, Sciuridae, pp. 648-837 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions</i> on page 744, DOI: 10.5281/zenodo.6840226