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The WPA included 35.8 ha of wetland and 116.5 ha of upland (Fig. 1). The upland consisted of a 2.5-ha treebelt (TB) planted in 1968 to Russian olive (Elaeagnus angustifolia), chokecherry (Prunus virginiana), plum (Prunus spp.), red-osier dogwood (Cornus stolonifera), and lilac (Syringa spp.); a 2.3-ha island of native prairie (NP) in a seasonally flooded wetland, and 6 fields 14.0-27.0 ha in size. The fields were seeded with a mixture of wheatgrass (Agropyron spp.), switchgrass (Panicum virgatum), needlegrass (Stipa spp.), and alfalfa (Medicago sativa) in 1963. One field (UN) was left untilled after 1963. Other fields (DC3, DC5, DC6, DC8, DC9) were subsequently cultivated and seeded during different years to a DNC mixture of wheatgrass, alfalfa, and sweetclover (Melilotus spp.). Age of DNC in each field in 1982 was 3, 5, 6, 8, and 9 years, respectively. Selected areas on the WPA were occasionally mowed or burned. A 12.2-ha area, including portions of fields UN and DC8, was surrounded by an electric fence designed to repel certain duck nest predators (Lokemoen et al. 1982).

Figure 1.  Distribution of 4,430 telemetry locations of active adult ground squirrels on and adjacent to a 152-ha WPA during 1981-82. All 0.5- × 0.5-m grid squares in which >1 location occurred are shaded. Habitat codes represent 3-, 5-, 6-, 8-, and 9-year-old dense mesting cover fields (DC3, DC5, DC6, DC8, DC9), 19-year-old untilled field (UN19), treebelt (TB), and an island of native prairie in a seasonally flooded wetland (NP).