Washington ground squirrel (Spermophilus washingtoni)

Synonyms: Urocitellus washingtoni
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderRodentia
FamilySciuridae
GenusSpermophilus (1)
SizeHead-body length: 15.3 - 19.5 cm (2)
Tail length: 3.2 - 5 cm (2)
Weight107 - 300 g (2)

The Washington ground squirrel is classified as Near Threatened (NT) on the IUCN Red List (1).

The Washington ground squirrel (Spermophilus washingtoni) is a small, smoky grey-brown squirrel with small, rounded ears and conspicuous, slightly square white spots on the upperparts (2) (3) (4) (5). The underparts are grey-white and the feet are white, and both have a buffy-pink tinge (2) (3) (5). The contrast between the upperparts and underparts creates a strong line running along the sides of the body (3).

The grey-brown tail of the Washington ground squirrel is short and grizzled, with cream edges and a pink-cinnamon underside (2) (3). The snout is orange above and pink-cinnamon underneath, contrasting with the white throat (2) (3). The fur of the Washington ground squirrel becomes slightly browner as it wears (5).

The calls of the Washington ground squirrel are soft, squeaky, lisping whistles (2) (4) (5). When calling to draw attention to danger this species stands erect, then swiftly returns to its burrow (2).

The Washington ground squirrel, as its name suggests, is found in Washington and Oregon in the United States (1) (3) (6). It is found on the Colombia Plateau in an area of less than 20,000 square kilometres, to the south and east of the Colombia River (5) (6).

The Washington ground squirrel inhabits arid, open sagebush (Artemisia spp.) and grassland (2) (3) (5) (6) (7) (8), where the soil is sandy, soft and deep enough to build underground burrows (2) (5) (6) (7). Areas with high grass cover are preferred and support the most abundant populations (1) (5) (6). This species is found at elevations between 90 and 450 metres (1). 

The Washington ground squirrel can be solitary or live in colonies (1), with females occasionally forming coalitions. These coalitions usually consist of between two and four females, who build burrows and raise their young together, as well as sharing responsibility for defending the burrow from any predators (7). The burrows of the Washington ground squirrel can be up to 1.7 metres deep and over 7 metres long (5).

The breeding season begins shortly after the Washington ground squirrel emerges from hibernation in late January or early February, and lasts for several weeks (1) (5) (8). Emergence from the burrow and breeding can happen up to a month later at higher elevations (1) (5). Males of this species usually emerge from hibernation earlier than the females (5).

The female Washington ground squirrel gives birth to a single litter of between 5 and 11 young in February or early March, after a gestation period of 23 to 30 days (1) (2) (5). The young are weaned and begin to emerge from the burrows in late March, and are nearly adult size by the end of May (1) (5).

In May or June adult Washington ground squirrels enter a period of dormancy, while juveniles generally wait until June or July (1) (2) (8). The hibernation period of the Washington ground squirrel lasts for seven or eight months, leaving only a small proportion of the year for reproducing, foraging and accumulating body fat (1) (8). While it is not hibernating, this species is diurnal and is mostly active in the morning, especially when temperatures are high (1) (2) (5).

The diet of the Washington ground squirrel consists mostly of herbaceous vegetation, as well as flowers, roots, bulbs and seeds as well as insects (1) (2) (5). A high-energy diet is important for providing this species with the necessary body fat reserves to survive its long period of dormancy (7).

Habitat loss and fragmentation are probably the biggest threats to this habitat specialist, which requires a specific soil type to excavate its burrows (1). Urbanisation, agriculture and irrigation have lead to previously suitable habitat becoming unfit for the Washington ground squirrel (1) (2) (6) (7), with up to two-thirds of its previous range thought to have been converted for agriculture. Isolated populations of the Washington ground squirrel are also threatened by inbreeding (7).

The native plants eaten by the Washington ground squirrel have largely been replaced by non-native, exotic perennials, or have been grazed by other animals or lost due to fires. The low energy content of non-native plants may prevent the Washington ground squirrel from gaining enough body fat to survive through the hibernation period. These plants may also reproduce asexually, and do not produce the high-energy seeds required by this species (7).

Considered to be a pest in some areas, the Washington ground squirrel has been a victim of shooting and poisoning, and has previously been targeted by control programmes (1) (2) (5) (6). Parasites and diseases are also threats to this species (1) (7), especially sylvatic plague, which has previously reduced the population of another species of ground squirrel, Townsend’s ground squirrel (Spermophilus townsendii) (1) (7).

Natural predation by larger mammals and birds of prey can be critical for small, isolated populations of the Washington ground squirrel (1) (6) (7).

The area which is known to support the largest population of Washington ground squirrels, the Boardman Bombing Range, is not entirely protected. The majority of this area is managed by the U.S. Navy, with a small proportion owned by the Nature Conservancy, which aims to conserve this species and its habitat. In Washington, most of the Washington ground squirrel’s habitat is protected and falls within the Seep Lakes Wildlife Management Area (1).

Some privately owned land which was due to be converted for agriculture has been given to the Oregon Department of Fish and Wildlife Conservation Easement (1) (9), which should protect and maintain one of the largest suitable habitats for the Washington ground squirrel. However, populations on other privately owned lands still remain under threat from habitat loss and require the same protection through Conservation Easements (1). This may require providing incentives for private landowners to preserve the habitat. Priority for conservation should be given to continuous areas of suitable habitat which are able to support large populations of Washington ground squirrels (7).

More research and further surveys are also needed to provide appropriate conservation measures for the Washington ground squirrel (1).

Discover more about the Washington ground squirrel:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

  1. IUCN Red List (April, 2012)
    http://www.iucnredlist.org/
  2. Reid, F. (2006) Mammals of North America. Peterson Field Guides, New York.
  3. Kays, R., Kays, R.W. and Wilson, D.E. (2009) Mammals of North America. Princeton University Press, Princeton.
  4. Bowers, N., Bowers, R. and Kaufman, K. (2007) Kaufman Field Guide to Mammals of North America. Houghton Mifflin Harcourt, New York.
  5. Rickart, E.A. and Yensen, E. (1991) Spermophilus washingtoni. Mammalian Species, 371: 1-5. Available at:
    http://www.science.smith.edu/msi/pdf/i0076-3519-371-01-0001.pdf
  6. Hafner, D.J., Yensen, E. and Kirkland, G.L. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Cambridge, UK. Available at:
    http://data.iucn.org/Themes/ssc/actionplans/northamericanrodents/contents.pdf
  7. Sherman, P.W. and Shellman Sherman, J. (2011) Distribution, Demography, and Behavioral Ecology of Washington Ground Squirrels (Urocitellus washingtoni) in Central Washington. Cornell University, New York. Available at:
    ftp://ftp2.fs.fed.us/incoming/r6/ro/issssp/Project_reports/SDO_WA_grnd_squirrel_report_2011.pdf
  8. MobileReference (2008) Encyclopedia of North American Mammals. MobileReference, Boston.
  9. Oregon Department of Fish and Wildlife (April, 2012)
    http://www.dfw.state.or.us/