The ground squirrels were formerly under the genus Citellus (Tomich, 1982).
Formerly, this species was split into two subspecies, S. w. washingtoni and S. w. loringi, but in 1948, Dalquest synonymized these into a single group after finding no comparable difference in size (Verts and Carraway, 1998).
S. washingtoni is of the subgenus Spermophilus (Nowak, 1997)
Spermophilus is derived from the vernacular "spermophile," or lover of seeds (Tomich, 1982).
Washington ground squirrels probably use a variety of acoustic, visual, tactile, and chemical forms of communication, though little research has been done on this to date. They use the same suite of senses to perceive their environment.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
According to the IUCN Red list of Threatened Species, the Vulnerable listing of S. washingtoni is due to the increasing fragmentation and loss of its habitat, particularly within the last decade.
The U.S. Fish & Wildlife Services Threatened and Endangered Species System has not yet determined the status of S. washingtoni. It is currently listed as a candidate taxon and is ready for proposal (U.S. F&WS, 2001).
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: near threatened
Spermophilus washingtoni is an agricultural pest. It eats wheat, oats, alfalfa and other agricultural products of the region (ASM, 2000; Verts and Carraway, 1998).
Negative Impacts: crop pest
Washington ground squirrels are important parts of healthy Columbian ecosystems.
Washington ground squirrels are important members of the ecosystems in which they live. They are important in influencing the composition of regional plant communities through their grazing and in nutrient cycling through their burrowing activities.
Ecosystem Impact: disperses seeds
Spermophilus washingtoni feed primarily on grasses until about June when the green of the plants is desiccated. They then feed mostly on seeds of the same grasses (Verts and Carraway, 1998).
Plants eaten include: needle-and-thread grass, Stipa comata, Sandberg grass, Poa sandbergii, cheat grass, Bromus tectorum, globemallow Sphaeralcea, plantain, Plantago, Indian ricegrass, Oryzopsis, tumblemustard Sisymbrium, alfalfa, oats and wheat (Verts and Carraway, 1998).
Plant Foods: leaves; seeds, grains, and nuts
Primary Diet: herbivore (Folivore , Granivore )
Spermophilus washingtoni is found in the low elevation Columbia basin of southeastern Washington state east of the Columbia River (Burke, 2001) and northeastern Oregon. In Oregon they occur in Gilliam, Morrow, and Umatilla counties (ASM, 2000). The original range is dramatically reduced because of habitat destruction (Verts and Carraway, 1998).
Biogeographic Regions: nearctic (Native )
Native habitats in the low elevation Columbia basin is mainly native bunchgrasses and sagebrush. Grazing, fire, cultivation and irrigation has dramatically altered the habitat of S. washingtoni. Big sagebrush, Artemisia tridentata and bluebunch wheatgrass, Agropyron spicatum once dominated this "shrub-steppe" region. However, the original plant species have mostly been replaced (in non-agricultural areas) by rabbit-brush, Chrysothamnus viscidiflorus and cheat grass, Bromus tectorum (Verts and Carraway, 1998).
These ground squirrels are most abundant in areas with sandy or soft soils that are well-drained and deep, facilitating burrowing, and in areas with abundant grass.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland ; chaparral
No information is available on the average lifespan of S. washingtoni.
Similar to other ground squirrel species, Spermophilus washingtoni individuals have short legs and small, rounded ears. The tail is short (32-65 mm), the rounded eyes are set high on the head, the postorbital processes are well developed, and the zygomatic arches expand posteriorly. The cheek teeth are high crowned.
Greyish-white spots about 4 mm across mark the smoky-grey base color on their backs. The underside is grayish-white and extends up the sides of the body to a line connecting the shoulder and thighs. There is a white eye-ring. Weight varies seasonally between 120 and 300 grams. Males are slightly larger than females, with total body lengths of males and females ranging from 185 to 245 mm.
Spermophilus washingtoni can be distinguished from other grounds squirrels (S. washingtoni and S. beldingi) in the same area because they are smaller, with smaller ears and a spotted pelage, which the other two species lack. Spermophilus washingtoni have a hind foot of less than 43 mm, whereas the other two species have longer hind foot lengths.
Range mass: 120 to 300 g.
Range length: 185 to 245 mm.
Other Physical Features: endothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger
Although S. washingtoni have a large number of predators, their fossorial lifestyle protects them from a high predation rate (Hamilton, 1939).
Most isolated subpopulations are vulnerable to the threat of extinction due to the conversion of rangeland to agricultural land, and due to poisoning and shooting (IUCN, 2000).
Known Predators:
Males emerge from hibernation before females and compete for access to females as they emerge. Once mating is completed, there is no further interaction between males and females.
Mating System: polygynous
Only one litter per year is produced due to the small amount of time S. washingtoni are active above ground (Verts and Carraway, 1998). Litter size ranges from five to eleven (Verts and Carraway, 1998) and an average of eight embryos was found in a sample of 26 S. washingtoni (Hayssen et al., 1993).
The reproductive season begins in January and sometimes lasts through April. Breeding occurs in late January and early February (Verts and Carraway, 1998). Young are birthed in late February and March in Washington and mostly in March in Oregon (Hayssen et al., 1993).
Spermophilus washingtoni reaches sexual maturity early and first breed as yearlings (Verts and Carraway, 1998).
In 1941, T. Scheffer reported that S. washingtoni are polygamous, but little else has been reported on mating behavior or parental care.
Breeding interval: Breeding occurs once yearly.
Breeding season: Breeding occurs in late January and early February.
Range number of offspring: 5 to 11.
Average weaning age: 1 months.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
The young are birthed underground in burrows and emerge by March (Hayssen et al., 1993). They are altricial and at birth their eyes and ears are closed and no teeth have erupted. However, development is rapid and within 10 days head and body hair is present. After about 15 days the incisors erupt, and the eyes open within 20 days (Tomich, 1982). In late March, when about 1 month old, babies weigh from 22 to 44 grams (Hayssen et al., 1993) and average 38.8 grams (Verts and Carraway, 1998). Weaning takes place in the first month, and after one month no milk curd is found in the stomachs of some captured individuals (Verts and Carraway, 1998). By late April, the average mass is 116 grams (range: 89 - 139 grams). The mass by late May ranges from 147 to 205 grams. The male ranges from 175 to 205 grams and the females ranges from 147 to 193 grams.
Males do not care for young.
Parental Investment: altricial ; pre-fertilization (Provisioning); pre-hatching/birth (Provisioning: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
The Washington ground squirrel (Urocitellus washingtoni) is a squirrel that lives in the Pacific Northwest states of Washington and Oregon, United States.
The Washington ground squirrel lives in sagebrush or grassland habitats in the Columbia River Basin of Washington and Oregon. Washington ground squirrels hibernate / estivate 7–8 months each year. Adults breed shortly after emergence from hibernation in January or February and juveniles emerge from the natal burrow in March. Juveniles disperse away from the natal burrow and settle into new areas. All Washington ground squirrels gain weight and prepare for hibernation in late spring and early summer. Juveniles immerge for estivation in June or July, and adults begin estivating earlier, often in June.
One radiotracking study focused on dispersal of Washington ground squirrels.[2] It found that 72% percent of juvenile males dispersed in April. Dispersal distances ranged from 40 to 3521 meters and the median dispersal distance was 880 meters. Twenty to 56% of radio-collared juvenile squirrels survived to estivation. Raptors and badgers were the primary causes of mortality. Survival rates of dispersers were higher than non-dispersers, mostly due to badger predation on natal sites.
The species is listed as endangered in Oregon and is a candidate for endangered species listing in the United States, but is not currently listed. The IUCN formerly listed the species as vulnerable, but currently it is listed as near threatened.[1]
The Washington ground squirrel (Urocitellus washingtoni) is a squirrel that lives in the Pacific Northwest states of Washington and Oregon, United States.
