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		Figure 1.   The Waubay study area, Day County, South Dakota, 1950-1953 and 1992-1993.

The area covers approximately 29 km² of the Coteau des Prairies physiogeographic region (Van Bruggen 1985), most of which is privately owned and which supports a large diversity of birds, mammals, reptiles, and amphibians (Appendices A-C).

The study area is in the tall-grass prairie region of South Dakota (Johnson and Nichols 1982). Dominant grasses that formerly occupied this region include big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), switchgrass (Panicum virgatum), and indiangrass (Sorghastrum nutans). Untilled native prairie still exists on 24% of the study area, mostly as pasture or annually hayed grasslands.

Climate

Past and present weather data were obtained from records maintained at the Waubay National Wildlife Refuge. The climate of eastern South Dakota is typically mid-continental with great annual and seasonal variation. Summers are short and warm, and winters are long and cold. The highest recorded temperature at Waubay National Wildlife Refuge was 40.6° C on June 30, 1963. The coldest recorded temperature was -37.2° C on January 15, 1972. The mean high temperature extreme during 1954-93 was 36.4° C, and the mean low temperature extreme during 1954-93 was -33.2° C.

Annual precipitation from 1954 to 1993 ranged from 17.8 cm in 1976 to 81.8 cm in 1962 (Fig 2), primarily in the form of rain and most abundantly during April-August (Table 1). Snow accumulates in most years, and the wetlands are dependent upon runoff received from snowmelt.

Figure 2.   Annual precipitation (cm, in.) in the Waubay study area, Day County, South Dakota, 1950-1993.