Western Gray Squirrel
Encyclopedia
The Western Gray Squirrel (Sciurus griseus) is an arboreal rodent
found along the western coast of the United States
and Canada
.
In some places, this species has also been known as the Silver-gray Squirrel, the California Gray Squirrel, the Oregon Gray Squirrel, the Columbian Gray Squirrel and the Banner-tail. There are three geographical subspecies: Sciurus griseus griseus (central Washington to the western Sierra Nevada in central California
); S. g. nigripes (from south of San Francisco Bay to San Luis Obispo County, California
; and S. g. anthonyi, which ranges from San Luis Obispo
to northern Baja California
).
in 1818 based on notes taken by Lewis and Clark at The Dalles in Wasco County, Oregon
.
Compared with the Eastern Gray Squirrel
S. carolinensis or the Eastern Fox Squirrel (which have been introduced into its range), these squirrels are shy, and will generally run up a tree and give a hoarse barking call when disturbed. Weight
s vary from about 0.4 to 1 kg (14.1 to 35.3 oz), and length (including tail) from 45 to 60 cm (17.7 to 23.6 in). It is the largest native tree squirrel in the western coastal United States. Western Gray Squirrels exhibit a form of coloration known as counter shading. The dorsal fur is a silver gunmetal gray, with pure white on the underside; there may be black flecks in the tail. Ears are large but without tufts. The ears turn reddish-brown at the back in the winter. The tail is long and typically very bushy. Tree squirrels undergo a complete head-to-tail molt in the spring and a rump-to-head molt in the fall. Tail hair is replaced only in the spring. Also, nesting mothers will use their tail hair to line birthing nests. They eat berries, nuts, and small birds eggs occasionally. Also many different seeds.
s which remain in the nest for a longer period that other squirrels. The kits are relatively slow in development, and will not leave the nest for six months or more - another species disadvantage when in competition with other, more-rapidly fledging squirrels. Young gray squirrels have furled tails which will not reach fullness until adulthood. This is a good indicator of age and maturity. Mother squirrels often seem to be overworked with a stressed appearance, complete with bruised and battered nipples. Mating squirrels can be very sadistic and will bite and injure each other. Females can be quite territorial, and will chase others away and have fairly violent altercations between themselves.
dwellers, and can be found at elevations up to at 2,000 m or more. Time on the ground is spent foraging, but they prefer to travel distances from tree to tree. They are strictly diurnal
, and feed mainly on seeds and nuts, particularly pine seeds and acorn
s, though they will also take berries, fungus and insects. Pine nuts and acorns are considered critical foods because they are very high in oil and moderately high in carbohydrates, which help increase the development of body fat. They feed mostly in trees and on the ground. They generally forage in the morning and late afternoon for acorns, pine nuts, new tree buds, and fruits. When on alert, they will spread their tails lavishly, creating an umbrella effect that shields them and possibly provides cover from overhead predators. They are scatter-hoarder
s making numerous caches of food when it is abundant, and thus contribute to the seed dispersion of their food trees. Although squirrels show relatively good scent relocation abilities, some food caches are never reclaimed, becoming seedlings in the spring. Though they do not hibernate, they do become less active during the winter. Like many prey animals, they depend on auditory alerts from other squirrels or birds to determine safety. Once an alarm call is transmitted, those present will join in, and the trees become a cacophony of barking squirrels. Tree squirrels are prey for bobcat
s, hawk
s, eagle
s, mountain lions and coyote
s.
, lichens and shredded bark. The birthing nest may be lined with tail hair. The nest may measure 43 to 91 cm (17 to 36 in) by up to 46 cm (18 in) and is usually found in the top third of the tree. Young or traveling squirrels will also "sleep rough" when weather permits, balanced spread-eagled on a tree limb high above the forest floor. This attitude is also adopted for cooling in hot weather, a behaviour also observed in raccoons.
, a disease caused by mites, becomes epidemic in Western Gray Squirrel populations and is a major source of mortality. Other species of Eastern Gray Squirrels, fox squirrels, California ground squirrels and Wild Turkey
s are expanding and compete with the Western Gray.
Listed as extirpated in some California areas, the Western Gray Squirrel in southern California is generally found only in the mountains and surrounding foothill communities. Local rehabilitation experts recount the Eastern Fox Squirrels were released in urban regions Los Angeles throughout the 20th Century. Fox squirrels (Sciurus niger) were introduced to the Los Angeles area in about 1904. Civil war and Spanish American war veterans residing at the Sawtelle Veteran’s Home on Sepulveda and Wilshire Boulevards brought fox squirrels as pets to this site from their homes in the areas surrounding the Mississippi Valley (possibly Tennessee). Other introductions of fox squirrels to the Los Angeles area may have taken place during more recent times but detailed records are not available. These aggressive cousins drove the more reclusive Western Grays back into the mountains, where competition was not so strong. This non-native species introduction appears to be the largest threat in the southern California area.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
found along the western coast of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
In some places, this species has also been known as the Silver-gray Squirrel, the California Gray Squirrel, the Oregon Gray Squirrel, the Columbian Gray Squirrel and the Banner-tail. There are three geographical subspecies: Sciurus griseus griseus (central Washington to the western Sierra Nevada in central California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
); S. g. nigripes (from south of San Francisco Bay to San Luis Obispo County, California
San Luis Obispo County, California
San Luis Obispo County is a county located along the Pacific Ocean in the Central Coast of the U.S. state of California, between Los Angeles and the San Francisco Bay Area. As of the 2010 census its population was 269,637, up from 246,681 at the 2000 census...
; and S. g. anthonyi, which ranges from San Luis Obispo
San Luis Obispo, California
San Luis Obispo is a city in California, located roughly midway between San Francisco and Los Angeles on the Central Coast. Founded in 1772 by Spanish Fr. Junipero Serra, San Luis Obispo is one of California’s oldest communities...
to northern Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
).
Description
The Western Gray Squirrel was first described by George OrdGeorge Ord
George Ord was an American ornithologist.Ord was born in Philadelphia, Pennsylvania. His father was a rope maker and Ord joined him in the business, continuing after his father's death in 1806...
in 1818 based on notes taken by Lewis and Clark at The Dalles in Wasco County, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
.
Compared with the Eastern Gray Squirrel
Eastern Gray Squirrel
The eastern gray squirrel is a tree squirrel in the genus Sciurus native to the eastern and midwestern United States, and to the southerly portions of the eastern provinces of Canada...
S. carolinensis or the Eastern Fox Squirrel (which have been introduced into its range), these squirrels are shy, and will generally run up a tree and give a hoarse barking call when disturbed. Weight
Weight
In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...
s vary from about 0.4 to 1 kg (14.1 to 35.3 oz), and length (including tail) from 45 to 60 cm (17.7 to 23.6 in). It is the largest native tree squirrel in the western coastal United States. Western Gray Squirrels exhibit a form of coloration known as counter shading. The dorsal fur is a silver gunmetal gray, with pure white on the underside; there may be black flecks in the tail. Ears are large but without tufts. The ears turn reddish-brown at the back in the winter. The tail is long and typically very bushy. Tree squirrels undergo a complete head-to-tail molt in the spring and a rump-to-head molt in the fall. Tail hair is replaced only in the spring. Also, nesting mothers will use their tail hair to line birthing nests. They eat berries, nuts, and small birds eggs occasionally. Also many different seeds.
Reproduction
Western Gray Squirrels mate over an extended period ranging from December through June. Young are born after approximate 44 day gestation period. Juveniles emerge from nests between March and mid-August. Litter sizes range from one to five kitKit
-Animals:* kit, a young ferret* a short form of kitten, a young cat* Kit fox, a relatively common North American fox* Kit, a group of domestic pigeons trained to perform together in competitions-Companies and organisations:...
s which remain in the nest for a longer period that other squirrels. The kits are relatively slow in development, and will not leave the nest for six months or more - another species disadvantage when in competition with other, more-rapidly fledging squirrels. Young gray squirrels have furled tails which will not reach fullness until adulthood. This is a good indicator of age and maturity. Mother squirrels often seem to be overworked with a stressed appearance, complete with bruised and battered nipples. Mating squirrels can be very sadistic and will bite and injure each other. Females can be quite territorial, and will chase others away and have fairly violent altercations between themselves.
Behavior/Diet
Western Gray Squirrels are forestForest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
dwellers, and can be found at elevations up to at 2,000 m or more. Time on the ground is spent foraging, but they prefer to travel distances from tree to tree. They are strictly diurnal
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...
, and feed mainly on seeds and nuts, particularly pine seeds and acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
s, though they will also take berries, fungus and insects. Pine nuts and acorns are considered critical foods because they are very high in oil and moderately high in carbohydrates, which help increase the development of body fat. They feed mostly in trees and on the ground. They generally forage in the morning and late afternoon for acorns, pine nuts, new tree buds, and fruits. When on alert, they will spread their tails lavishly, creating an umbrella effect that shields them and possibly provides cover from overhead predators. They are scatter-hoarder
Scatter-hoarder
Hoarding or caching is a type of animal behavior where an animal will store its food in times of surplus for times when food is less plentiful...
s making numerous caches of food when it is abundant, and thus contribute to the seed dispersion of their food trees. Although squirrels show relatively good scent relocation abilities, some food caches are never reclaimed, becoming seedlings in the spring. Though they do not hibernate, they do become less active during the winter. Like many prey animals, they depend on auditory alerts from other squirrels or birds to determine safety. Once an alarm call is transmitted, those present will join in, and the trees become a cacophony of barking squirrels. Tree squirrels are prey for bobcat
Bobcat
The bobcat is a North American mammal of the cat family Felidae, appearing during the Irvingtonian stage of around 1.8 million years ago . With twelve recognized subspecies, it ranges from southern Canada to northern Mexico, including most of the continental United States...
s, hawk
Hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...
s, eagle
Eagle
Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...
s, mountain lions and coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...
s.
Habitat/Shelter
Squirrel nests are called dreys and can be seen in trees, built from sticks and leaves wrapped with long strands of grass. There are two stick nest types made by the Western Gray Squirrel: the first is a large, round, covered shelter nest for winter use, birthing, and rearing young. The second is more properly termed a "sleeping platform," a base for seasonal or temporary use. Both types are built with sticks and twigs and are lined with leaves, mossMoss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
, lichens and shredded bark. The birthing nest may be lined with tail hair. The nest may measure 43 to 91 cm (17 to 36 in) by up to 46 cm (18 in) and is usually found in the top third of the tree. Young or traveling squirrels will also "sleep rough" when weather permits, balanced spread-eagled on a tree limb high above the forest floor. This attitude is also adopted for cooling in hot weather, a behaviour also observed in raccoons.
Recent Troubles
The Western Gray Squirrel was listed as a threatened species in Washington state in 1993. Populations of the Western Gray Squirrel have not recovered from past reductions. They are threatened with habitat loss, road-kill mortality and disease. Habitat has been lost due to urbanization, catastrophic wild fires, and areas of forest degraded by fire suppression and overgrazing, allowing the invasion of Scotch Broom. Notoedric mangeMange
Mange is the common name for a class of persistent contagious skin diseases caused by parasitic mites. Since mites also infect plants, birds, and reptiles, the term "mange," suggesting poor condition of the hairy coat due to the infection, is sometimes reserved only for pathological...
, a disease caused by mites, becomes epidemic in Western Gray Squirrel populations and is a major source of mortality. Other species of Eastern Gray Squirrels, fox squirrels, California ground squirrels and Wild Turkey
Wild Turkey
The Wild Turkey is native to North America and is the heaviest member of the Galliformes. It is the same species as the domestic turkey, which derives from the South Mexican subspecies of wild turkey .Adult wild turkeys have long reddish-yellow to grayish-green...
s are expanding and compete with the Western Gray.
Listed as extirpated in some California areas, the Western Gray Squirrel in southern California is generally found only in the mountains and surrounding foothill communities. Local rehabilitation experts recount the Eastern Fox Squirrels were released in urban regions Los Angeles throughout the 20th Century. Fox squirrels (Sciurus niger) were introduced to the Los Angeles area in about 1904. Civil war and Spanish American war veterans residing at the Sawtelle Veteran’s Home on Sepulveda and Wilshire Boulevards brought fox squirrels as pets to this site from their homes in the areas surrounding the Mississippi Valley (possibly Tennessee). Other introductions of fox squirrels to the Los Angeles area may have taken place during more recent times but detailed records are not available. These aggressive cousins drove the more reclusive Western Grays back into the mountains, where competition was not so strong. This non-native species introduction appears to be the largest threat in the southern California area.