Additional information on the distributions of small mammals at the Hanford Site, Washington
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The Hanford Site is a refuge for shrub-steppe organisms, including several small mammal species of concern in Washington, USA. We inventoried species occurrence and relative abundance of small mammals in areas of Hanford that had not been surveyed extensively. During 1997 and 1998, we performed trapping surveys for shrews and small rodents; visual searches and trapping surveys for ground squirrels (Spermophilus washingtoni); and spotlight surveys for jackrabbits (Lepus californicus). We captured nine small mammal species during 21 743 trap days/nights with snap traps, Sherman traps, pitfall traps, Tomahawk traps, and rat traps. The Great Basin pocket mouse and deer mouse dominated captures. Total captures were highest in antelope bitterbrush (Purshia tridentata)/Indian ricegrass (Oryzopsis hymenoides) dune communities. Capture rates were lowest in cheatgrass (Bromus tectorum) fields. In contrast to most upland habitats at low elevation on Hanford, deer mice were captured in relatively high numbers near active dunes. Northern grasshopper mice (Onychomys leucogaster) were captured in low elevation sandy areas, with most captures in a large needle-and-thread patch. We observed and captured Washington ground squirrels (Spermophilus washingtoni) within Hanford's northern boundary. Only six jackrabbits were seen during 118.5 km of spotlight surveys. We did not observe or capture Merriam's shrew (Sorex merriami), least chipmunk (Tamias minimus), Piute ground squirrel (Spermophilus mollis), or Ord's kangaroo rat (Dipodomys ordii). Low elevation areas of Hanford support a different small mammal fauna than higher elevation shrub-steppe areas on nearby lands of the Arid Lands Ecology Reserve and the Yakima Training Center.