Mammals 



We documented large and medium-sized mam- 

 mals (lagomorphs or larger) whenever encoun- 

 tered, but made no attempt to sample them 

 systematically. We inspected dens for evidence of 

 recent or current occupancy and sampled prey 

 remains if available, and we traversed the densest 

 and most extensive stands of big sagebrush 

 {Artemisia tridentata) looking for sign (pellets, 

 burrows) of Pygmy Rabbit (Brachylagus 

 idahoemis). When traversing areas of moderate 

 to dense cover, two observers followed separate 

 routes to increase the likelihood of flushing cotton- 

 tails or jackrabbits. 



Our intensive small mammal sampling involved 

 systematic trapping and examination of r^tor 

 pellets for skulls. We deployed 3 trap types (live 

 traps, snap traps, and pitfall traps) along line 

 transects or drift arrays to sample small mammals. 

 Different species of small mammals are more or 

 less likely to be captured using any single trapping 

 method (Jones etal. 1996, Allen etal. 1997), so 

 we used a variety of trapping techniques to 

 increase the probability of detecting the complete 

 small mammal fauna Shrews (Soricidae) in 

 particular are most likely to be captured using 

 pitfall traps. We placed trap transects selectively 

 (Appendix 3) to sample a variety of terrain repre- 

 senting different succession classes, rather than 

 distributing them randomly or systematically Total 

 trapping effort included 2772 live and snap trap 

 nights and 8380 pitfall trap nights (Table 1 ). 



We placed both live traps (folding Sherman traps 

 7.6 X 8.9 X 22.9 cm, model LFATDG) and snap 

 traps (Museum Special) together on transects of 

 30 stations, with stations spaced approximately 10 

 m apart in roughly a straight line. One live trap 

 and 2 snap traps were placed at each station 

 within one meter of the station. Live traps were 

 baited with a commercial seed mixture of millet, 

 cracked com, and sunflower seed; a small wad of 

 polyester fiber material was placed in the back of 

 traps to provide insulation for potential trapped 

 animals. Snap traps were baited with a mixture of 

 rolled oats and peanut butter. Traps were placed 

 late on one day and left in place for 3 or 4 nights, 

 with daily morning visits to document captures. 

 We closed snap traps during the day to minimize 

 capture of diurnal birds and recaptures of chip- 

 munks {Eutamias minimus), live traps remained 

 open. Atotalof 11 live/snap trap transects were 

 run during summer (Figure 1 ), 3 during each visit 

 except two in September During the last 2 

 sample periods (late July, late September) only 

 snap traps were deployed, as live traps were more 

 time consuming to use and captures in live traps 

 were very low. 



We established 6 pitfall transects (Figure 1 ) on 25 

 and 26 May. Pitfall traps used were coffee cans 

 (15x17 cm) buried with the rim flush to the 

 ground surface. Pitfall transects consisted of 1 

 cans, one per station, placed in a relatively straight 

 line approximately 30 m apart. We checked pitfall 

 traps daily when we were at the site and left them 



TABLE 1 . Total trapping effort (trap nights) in the Centennial Sandhills, 

 Beaverhead County, Montana in 1999. 



