Spermophilus washingtoni

Geographic Range

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 nearctic
  • native native

Habitat

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 temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• chaparral chaparral

Physical Description

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. columbianus 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.

• Other Physical Features
• endothermic endothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

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 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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous 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 altricial
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • provisioning
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

No information is available on the average lifespan of S. washingtoni .

Behavior

Spermophilus washingtoni is a fossorial species. They construct elaborate subterranean chambers, used year after year and expanded each season. Burrows are closed during periods of inactivity (Hamilton, 1939). Washington ground squirrels may spend up to 8 months of the year in hibernation or aestivation.

The annual cycle consists of successive periods of fattening, torpor, and reproduction. Emergence from winter dormancy resets this cycle. Hibernation begins with the onset of cold weather and aestivation may occur during dry, summer months. (Tomich, 1982)

Spermophilus washingtoni is a colonial species, but little other research is currently available on social behavior (Verts and Carraway, 1998). In areas with good habitat, densities may reach 250 per hectare.

Of the short-tailed ground squirrels, S. washingtoni is sympatric or parapatric with only S. columbianus and S. beldingi (Verts and Carraway, 1998). These squirrels are active during the day.

• Key Behaviors
• fossorial fossorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• hibernation hibernation
• aestivation
• colonial colonial

Communication and Perception

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 visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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).

• Primary Diet
• herbivore herbivore
  • folivore folivore
  • granivore granivore

• Plant Foods
• leaves
• seeds, grains, and nuts

Predation

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).

Ecosystem Roles

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

Economic Importance for Humans: Positive

Washington ground squirrels are important parts of healthy Columbian ecosystems.

Economic Importance for Humans: Negative

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

Conservation Status

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).

Other Comments

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).

Additional Links

Encyclopedia of Life

Contributors

Laura Merlo (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), University of Michigan-Ann Arbor.

References

Hall, E., K. Kelson. 1959. *The Mammals of North America, Volume 1* . New York, NY: The Ronald Press Company.

Hamilton Jr., W. 1939. *American Mammals; Their Lives, Habitats, and Economic Relations* . New York, NY: McGraw-Hill Book Company, Inc..

Hayssen, V., A. van Teinhoven, A. van Teinhoven. 1993. *Asdell's Patterns of Mammalian Reproduction* . London, UK: Comstock Publishing Associates, a division of Cornell University Press.

Nowak, R. 1997. "Walker's Mammals of the World Online" (On-line). Accessed 16 November 2001 at http://www.press.jhu.edu/books/walker/rodentia/rodentia.sciuridae.spermophilus.html .

Scheffer, T. 1941. Ground squirrel studies in the Four-Rivers Country, Washington. Journal of Mammology , 22: 270 - 279.

Tomich, P. 1982. *Wild Mammals of North America: Biology, Management, and Economics* "Ground Squirrels (*Spermophilus beecheyi* and Allies)" . Baltimore, MD: The Johns Hopkins University Press.

Verts, B., L. Carraway. 1998. *Land Mammals of Oregon* . Berkeley, CA: University of California Press.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals . Washington: The Smithsonian Institution Press.

2000. "2000 IUCN Red List of Threatened Species" (On-line). Accessed 01/10/05 at http://www.redlist.org/search/details.php?species=20475 .

2000. "American Society of Mammologists; Mammals of Oregon" (On-line). Accessed 01/10/05 at http://www.mammalsociety.org/statelists/ormammals.html .

2004. "Burke Museum of Natural History and Culture; Washington Ground Squirrel, *Spermophilus washingtoni*" (On-line). Accessed 01/10/05 at http://www.washington.edu/burkemuseum/collections/mammalogy/mamwash/spwa.html .

2001. "U.S. Fish & Wildlife Services: Species Information Threatened and Endangered Animals and Plants" (On-line). Accessed 01/10/05 at http://endangered.fws.gov/wildlife.html .