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Washington Ground Squirrel

Image of Washington ground squirrels

Scientific Name: Urocitellus washingtoni

Status: None

Potential Range Map

  • Introduction

    The Washington ground squirrel became a candidate species in October 1999.  The U.S. Fish and Wildlife Service reviews the status of this and all other candidate species annually.  

    Historical Status and Current Trends

    Washington ground squirrels are found in the Columbia Plateau of Washington and Oregon.  Historically, the species was distributed over much of the shrub-steppe habitat of southeastern Washington and northcentral Oregon, but its range has contracted due to habitat loss, primarily from agricultural development.   The Washington population occurs in Adams, Douglas, Franklin, Grant, Lincoln, and Walla Walla counties.  Its range appears to have been lost in Columbia, Garfield, Spokane, and Whiteman counties.  The Oregon population occurs in Gilliam, Morrow, and Umatilla counties.  The largest and most densely occupied area in Oregon occurs on the Naval Weapons Systems Training Facility - Boardman, managed by the U.S. Navy, and the adjacent Boardman Conservation Area, managed by The Nature Conservancy.  Washington ground squirrels were thought to be extirpated at most sites in Oregon outside this area, until recent surveys have documented a more expanded presence in the state.

    Habitat

    Washington ground squirrels inhabit sites with sandy or silt-loam texture soils that are deep and supportive enough to accommodate its burrow structures (Betts 1990, Yensen and Sherman 2003), and where there is sufficient forage.  Silt loam soils, especially those classified as Warden soils, may be the most important habitat feature.  Warden soils not only have a high silt content, they are very deep, allowing for deeper burrows that maintain their structure compared to sandy or shallow soils.  Historically Washington ground squirrels were primarily associated with sagebrush and bunchgrass habitat.  However, much of this habitat has been invaded with cheatgrass (Bromus tectorum) and rabbitbrush (Chrysothamnus sp.), and they are found in all of these habitat types today.  

    Life History

    The Washington ground squirrel spends much of its time underground.  Adults emerge from hibernation between January and early March, depending on elevation and microhabitat conditions, with males emerging before females.  Their active time is spent in reproduction and fattening for their six-month or longer dormancy.  Adults return to their burrows by late May to early June, and juveniles return about a month later.  Washington ground squirrels produce only one litter of young per year due to their limited period of activity and reproduction.

    Reasons for Decline

    Agricultural conversion of shrub-steppe habitat is the primary cause historically for the decline of the Washington ground squirrel.  Because the squirrel is so closely tied to deep, silty soils,  tilling and other mechanisms involved in conversion of shrub-steppe habitats to agricultural crop production destroys the species' food source and renders soils, that are necessary for burrowing, unusable.  These soils can either be irretrievably modified or take years to recover.  There are some anecdotal accounts of squirrels starting to re-occupy land enrolled in the Conservation Reserve Program, however, the ability to re-occupy an area depends on the historic and current land use of the property, as well as proximity of these areas to existing colonies.

    Another reason for this species’ historic decline is persecution.  Often viewed as pests, this species has also been subjected to recreational shooting and poisoning historically.

    Conservation Measures

    The Washington ground squirrel is listed as endangered under the Oregon Endangered Species Act and is a candidate species in Washington.  The U.S. Fish and Wildlife Service continues to work with state fish and wildlife agencies, private agricultural landowners, and other partners to conserve and monitor the status of this species.

    A key conservation milestone for the Washington ground squirrel was the development of a conservation agreement with Threemile Canyon Farms, The Nature Conservancy, Portland General Electric, and Oregon Department of Fish and Wildlife (ODFW) in 2004.  Under this agreement, 23,000 acres of important Washington ground squirrel habitat (the Boardman Conservation Area) is protected from future land development.   

    Another important milestone for conserving this species was the development and implementation of wind energy siting and permitting guidelines that help protect the Washington ground squirrel.  With stakeholder input, the Service, ODFW and Oregon Department of Energy finalized guidelines in 2008 that could be used for all permitting jurisdictional levels in the Oregon Columbia Plateau Ecoregion for wind power projects that generate under 105 MW.  In combination with similar protective guidelines that the Energy Facility Siting Council follows for larger wind projects, there is a mechanism to ameliorate the impact of energy development to squirrels on all projects.

    In 2015, we worked with the Foster Creek Conservation District to develop a conservation plan for multiple species in Douglas County, Washington.  This voluntary programmatic plan covers 879,000 acres.  Participating landowners will implement measures associated with agricultural activities for the conservation of Washington ground squirrel and three other sagebrush-steppe species. 

    The most recent partnership on behalf of the Washington ground squirrel is an agreement with the U.S. Navy to provide conservation measures that avoid, minimize and mitigate for the effects of ongoing and future military readiness activities on the Naval Weapons Systems Training Facility in Boardman, Oregon.     

    References

    Betts, B.J.  1990.  Geographic distribution and habitat preferences of Washington ground squirrels (Spermophilus washingtoni). Northwestern Naturalist 71:27-37.

    Yensen, E. and P.W. Sherman.  2003.  Ground-dwelling squirrels of the Pacific Northwest. Boise, ID. April  28 pp. + maps.

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