first reported the species in Montana, but there 

 have been few additional records (13 total in the 

 Heritage databases, including one in 1969 from an 

 unknown locality in the Centennial Valley). 



We failed to detect Pygmy Rabbit in our survey, 

 but there is a recent record ( 1 9 August 1 997) 

 from the West Hills (T13S,R2W,S14SW)ina 

 stand of dense big sage (Rauscher 1997, personal 

 communication). Both Black-tailed Jackrabbit and 

 Pygmy Rabbit may have entered the state follow- 

 ing an increase in sagebrush cover in southwestern 

 Montana since the late nineteenth century 

 (Hofl&nannetal. 1 969b, Amo and GrueU 1983, 

 Lesica and Cooper 1 997), as there are no Mon- 

 tana records for either species prior to 1 9 1 8. 

 Both are species of special concern in Montana 

 (Appendix 2). 



Rodents : We captured 137 individuals of 6 rodent 

 species (Appendices 4-6): 1 9 Least Chipmunk 

 {Tamias minimus), 17 Northern Pocket Gopher 

 {Thomomys talpoides), 6 Great Basin Pocket 

 Mouse (Perognathus parvus), 57 Deer Mouse 

 (Peromyscus maniculatus), 39 Montane Vole 

 {Microtus montanus), 1 Meadow Vole (M 

 pennsylvanicus), and 5 unidentifiable Microtus. 

 Deer Mouse was the most abundant small mam- 

 mal captured (1.84 captures/ 1 00 trap nights) and 

 occurred throughout the sandhills in most habitats 

 except in relatively dense low-stature sagebrush 

 froughs (frap line 3) and mesic grass/sedge bottom 

 (frap line 4). In these sites Montane Vole was the 

 only small rodent captured. Typically, where one 

 species was captured the other species was 

 caught far less or not at all (Appendix 4); only one 

 frap line (line 7) produced nearly equal numbers. 

 However, voles were more likely to be caught in 

 pitfalls (Appendix 5), and our collective data show 

 that Montane Vole was also widely distributed in 

 all habitats in the Sandhills. Meadow Vole, 

 however, was captured only once, on pitfall line 5 

 in the East Hills. 



Least Chipmunk {Eutamias minimus) and 

 Northern Pocket Gopher {Thomomys talpoides) 

 were captured in both the East and West Hills. 



Most captures were from dune crests and dune 

 slopes in erosion and deposition sites where 

 evidence of thefr burrows was also most evident, 

 consist L-tit with the observations of Lesica and 

 Cooper (1999). Chipmunks were rarely captured 

 (one of 1 9 individuals) on "flat" terrain (frap lines 

 4, 6, and 10: see Appendix 3). The same pattern 

 was evident with the pocket gopher; 1 2 of 1 3 

 captured (all juveniles) were on dune slopes, and 

 the one individual that wasn't was less than 20 m 

 from a dune slope. 



Great Basin Pocket Mouse {Perognathus 

 parvus) was captured 6 times, only in the East 

 Hills (Appendices 5 and 6) and perhaps related to 

 the late successional stage of the East Hills dunes. 

 Pocket mice dig burrows at the base of sagebrush 

 plants (Clark and Sfromberg 1985), which are 

 larger and more mature (making burrows more 

 stable) in the East Hills. Lower grazing intensities 

 in the East Hills also make available more forb and 

 grass seeds (Lesica and Cooper 1999), the 

 primary foods of the Great Basin Pocket Mouse 

 ( Verts and Kirkland 1988). 



Great Basin Pocket Mouse has been reported in 

 Montana fewer than ten times, with the bulk of 

 these records from 1961 (Hofl&nannetal. 1969b) 

 and no reports since then unril our 1999 collec- 

 tions. Our 1 999 collections also represent the first 

 documented occurrence for the Centennial Valley, 

 and a range extension about 60 km east from 

 Sage Creek near Dell. Great Basin Pocket 

 Mouse is a species of concern in Montana (Ap- 

 pendix 2). 



We did not trap Wyoming Ground Squirrel 

 {Spermophilus elegans) and observed few in the 

 Sandhills, although we found some skulls at 

 Coyote dens and in raptor pellets. Three were 

 observed in the East Hills at a cattle guard along 

 theroadinT13S,RlW,S28NEon 1 July,and2 

 were seen in the West Hills along the road in 

 T13S,R2W,S22NE. Both sightings were near 

 small stands of big sagebrush. This species was 

 formerly considered a race of Richardson's 

 Ground Squirrel {S. richardonii), and is found in 



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