Western Gray Squirrel
Sciurus griseus
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Painting by Todd Zalewski from Kays and Wilson's Mammals of North America, ę Princeton University Press (2002)

Description

The western grey squirrel ranges from about 18 inches to 24 inches in total length with the body and the tail. Their weight varies from 350 to 950 grams.

Sciurus griseus has silver grey fur on its back and a white underside. It has a long bushy tail which is the same silver grey color. Their tail may also have black in it. Sciurus griseus has large ears without tufts.

The western grey squirrel sheds its fur once in the late spring and again in early fall. The fur on the tail is only shed during the spring molting.

Length:
Range: 510-770 mm
 
Weight:
Range: 500-950 g
Range Map
 
 
Taxonomic Hierarchy

Spotted_Sandpiper_AllAm

Western grey squirrels  lives on the west coast of the United States. Western grey squirrels  can be found in Washington, Oregon, California, and in a very small part of Nevada.

Kingdom: Animalia
Phylum: Chordata
     Subphylum: Vertebrata
Class: Mammalia
    Subclass: Theria
        Infraclass: Eutheria
Order: Rodentia
    Suborder: Sciuromorpha
Family: Sciuridae
    Subfamily: Sciurinae
Genus: Sciurus
Species: Sciurus griseus
Reproduction & Life Cycle
Sexual maturity of Sciurus griseus is reached at 10 to 11 months. When Sciurus griseus is approximately one year old it will begin breeding. When a female is in estrus the vulva becomes pink and enlarged. When a male is sexually active the scrotum turns black from its original pinkish gray color. Breeding takes place once a year in the late spring. There are betwee 3 and 5 young per litter. Younger females generally have smaller litters than older females. The gestation period averages 43 days. Young are born without hair and with closed eyes and ears. The head and feet of young are large compared to the rest of the body. They are weaned at approximately 10 weeks.

Conservation Status

Western grey squirrels are a United States species of concern, but are not currently listed as threatened or endangered under the U.S. Endangered Species Act. In late 2002 the Washington subspecies, S. griseus griseus was proposed for listing as an endangered species. In Washington they are considered threatened at the state level, in Oregon they are considered a state sensitive species.

Habitat

Western grey squirrels are found in woodlands and coniferous forests. They can be found at elevations up to 2500 meters.

Behavior

Western grey squirrels live in hollow trees or in nests they build called dreys. These are made of sticks and lined and insulated with softer materials such as moss.

Sciurus griseus is diurnal. While out of the nest Sciurus griseus spends its time grooming, exploring, gathering food, and resting. Grooming can last from 3 to 15 minutes, with most of the time being spent on the head area. Western grey squirrels have a home range size of 0.5 to 7 hectares. Males generally have a larger home range than females. While exploring Sciurus griseus gathers food. Food they don't eat or take back to the nest is buried around their home range. The buried food is called a cache and is later found by their good sense of smell. Caches are usually used in the colder months when food is scarce.

Western grey squirrels do not hibernate but much less time is spent outside during the colder winter months.

Sciurus griseus is non-territorial except when the female is in estrus.

When threatened western grey squirrels make barking sounds while flicking their tails and stamping their feet.

Food

Western grey squirrel's main source of food depends largely upon local habitat characteristics. Those that live in coniferous forests feed primarily on seeds of pinecones. Those that live in hardwood forests feed largely on nuts and acorns. Sciurus griseus is also known to eat berries, fungus, bark, sap, and insects. It opens hard seeds and nuts using its incisors.

Western grey squirrels will feed on the ground as well as in trees.

Other Names

Sound

  • Gwi˝ver gris ar c'horn˘g (Breton)
  • Columbian Gray Squirrel (English)
  • Silver Gray Squirrel (English)
  • Western Gray Squirrel (English)
  • Ardilla gris (Spanish)
  • Sciurus griseus (Spanish)

They use a variety of sounds to communicate, including barks, chatters, distress screams, and high-pitched whines during mating.

IMGP2146.jpg (658981 bytes)
 
 
 
 
 
 
 

Sources used to Construct this Page:

Encyclopedia of Life

Animal Diversity Web

  • Alden, P., F. Heath, R. Keen, A. Leventer, W. Zomlefer. 1998. National Audubon society field guide to California. New York: Alfred A. Knopf.
  • Ingles, L. 1947. Mammals of the Pacific States. Stanford, California: Stanford University Press.
  • Linsdale, J. 1946. The California ground squirrel. Berkeley and Los Angeles: University of California press.
  • MacClintock, D. 1970. Squirrels of North America. New York and Toronto: Van Nostrand Reinhold Company.
  • Whitaker, Jr., J. 1980. National Audubon society field guide to North American mammals. New York: Alfred A. Knopf.
  • Boellstorff, D., D. Owings, M. Penedo, M. Hersek. 1994. Reproductive behaviour and multiple paternity of California ground squirrels. Animal Behaviour, 47(5): 1057-1064.
  • Cato, F. 2003. "San Diego Natural history Museum Field Guide: Spermophilus beecheyi" (On-line). Accessed June 17, 2003 at http://www.sdnhm.org/fieldguide/mammals/sper-bee.html .
  • Evans, F., R. Holdenried. 1943. A population study of the Beechey ground squirrel in Central California. Journal of Mammalogy, 24(2): 231-260.

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All photos ę 2008 Rick Swartzentrover - Free for non-profit use.

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