Introduction 



Extensive sandhills are rare in Montana. The 

 state's 2 major areas of sandhills lie at extreme 

 opposite comers of the state - the largest in 

 northeastem Montana near the Medicine Lakes in 

 Sheridan County, and the second largest in south- 

 westem Montana in the Centennial Valley of 

 Beaverhead County — both partially within 

 National Wildlife Refuges. While the flora of these 

 areas has been studied recently (Cooper et al. 

 1999, Lesica and Cooper 1999, Heidel et al. 

 2000), the fauna has not been as well docu- 

 mented, especially that of the Centennial Sandhills. 



Sandhills terrain is a product of wind and sand. 

 Sandhills occur in wind corridors where blowing 

 sand might be ftinneled, in the windward foothills 

 of mountain ranges, and in areas where wind 

 speeds are no longer sufficient to move sand any 

 farther or where improved growing conditions 

 increase the probability of dune stabilization by 

 plants. Sandhills are characterized by erodible, 

 well-drained soils that are very susceptible to 

 disturbances such as fire, grazing, and burrowing 

 (Knight 1 994). Sandhills often occur as isolated 

 patches across a regional landscape, and contrib- 

 ute significantly to local biodiversity by supporting 

 distinctive species and communities. Because 

 disturbance can easily alter these sites, sandhill 

 complexes support vegetation in various stages of 

 succession, often harboring early-succession 

 species and communities that are rare at local, 

 regional or global scales and dependent on distur- 

 bance for survival (Lesica and Cooper 1999). 

 For example, the Centennial Sandhills support 4 

 rare plant species that are restricted to early 

 succession sites (Lesica and Shelly 1991, Lesica 

 and Cooper 1999): Idaho painted milkvetch 

 (Astragalus ceramicus var. apus), Idaho pale 

 evening-primrose (Oenothera pallida var. 

 idahoensis), Fendler's cat's-eye (Cryptantha 

 fendleri), and sand wildrye (Elymusflavescens). 

 Sandhills habitats also support animal species of 

 limited distribution, some of which (usually inverte- 



brates) are sand-obligate species (Rumpp 1967, 

 Knisley 1979, Rust 1986). 



The flora and fauna of Beaverhead County, which 

 includes the Centennial Sandhills, have affinities to 

 the Great Basin (Dom 1978, Lesica et al. 1984, 

 Hofl&nann and Pattie 1968, Hoffinann et al. 

 1969b). These natural similarities distinguish this 

 sandhill complex from the Medicine Lake 

 Sandhills in northeastem Montana. Five mammal 

 species on the state special concern or watch lists 

 are limited to southwestern Montana (Black-tailed 

 Jackrabbit, Pygmy Rabbit, Wyoming Ground 

 Squirrel, Great Basin Pocket Mouse, Western 

 Spotted Skunk), and two other species of concern 

 (Preble's Shrew, Merriam's Shrew) are associated 

 with habitats found in the Centennial Valley, 

 especially sagebrush-steppe (Armstrong and 

 Jones 1971, Comely etal. 1992). 



In addition, the rare Idaho Dunes Tiger Beetle 

 (Cicindela arenicola), currently known only from 

 Idaho, occurs in the St. Anthony Dunes of Fre- 

 mont County (Rumpp 1967, Logan 1995, 

 Pearson et al. 1997) only 64 km (40 miles) south 

 of the Centennial Valley Sandhills. Because the 

 valley is remote and near the edge of several 

 species' distributions, and has not been well 

 surveyed, there is good potential to find this or 

 other species new to Montana, as well as, an 

 opportunity to document significant range exten- 

 sions of more common species. This is especially 

 true for small mammal and tiger beetle communi- 

 ties, since these groups contain species that are 

 habitat specific and/or are relatively obscure and 

 pooriy documented in Montana, particularly in 

 sandhills and shrub-grassland habitats. 



Because of the very limited distribution of sandhills 

 habitat in Montana and the distinctive nature of its 

 plants and animals, documenting the fauna is an 

 important first step toward effective management 

 of the biological diversity associated with these 

 habitats. The objectives of this study were to: 

 1 ) document the vertebrate species present in the 

 Centennial Sandhills; 



