During 1992-1993 lemmings were found at 10 of 17 sites that appeared to have suitable 

 lemming habitat. Either the lemmings were at all those sites and we failed to detect them, or we 

 sampled some sites with apparently good habitat, which actually lacked lemmings. Probably a 

 combination of the two is actually the case (Reichel and Beckstrom 1993, 1994). The percentage 

 of sites with good habitat which had lemming captures was slightly higher than that of Pearson 

 (1991) who found lemmings at 3 of 1 1 bog/fen sites trapped with Sherman live traps in 1989-90. 

 Bog lemmings have been found in at least nine community types (Table 4), including some of 

 those present at the sites trapped in 1996. However, peatland communities constitute a very 

 small proportion of the landscape in Montana and have not been adequately classified (Bursik 

 and Moseley 1992). Whether new information on these fens will result in newly defined 

 community types which closely approximate habitat used by northern bog lemmings remains to 

 be seen. Extensive thick moss mats were present in all but one of the lemming sites found during 

 our previous surveys (Reichel and Beckstrom 1993, 1994), and were also present at Numa Ridge 

 Bog, McGee Meadows (Pearson 1991, P. Lesica pers. comm.) and Shoofly Meadows (Pearson 

 1991, S. Chadde pers. coimn.). 



In 1993 I spent several hours along Camas Creek in the vicinity of the first lemming 

 population known from the state (Wright 1950) and found only scattered clumps of moss. 

 Weckwerth and Hawley (1962) did not adequately describe the two specific sites where they 

 captured bog lemmings, but they were visited by D. E. Pearson (pers. comm.) who found they 

 were not located in fens or covered by thick moss mats. At these three sites trapping was 

 conducted in multiple years, often twice each year (Camas Creek: 18 yrs [Hoffmarm et al. 1969]; 

 Anaconda #1 : 6 yrs spring and fall [Jonkel 1959]; Anaconda #6: 4 yrs spring and fall [Jonkel 

 1959]). Despite this intensive trapping, only a total of 3 individuals have been taken in Camas 

 Creek in 2 of 18 years, and 1 individual at each of the two Anaconda Creek sites. A similar 

 situation exists with the McDonald Creek site which is in old-growth western hemlock (Tsuga 

 heterophylla) forest (Pearson 1991); this site has been trapped multiple times yielding only a 

 single lemming (June 1991 - September 1993, total 3600 trap-nights, D. E. Pearson, pers. 

 comm.). Apparent high quality habitat patches exist within 7 km of all four sites (Table 9, 10; 

 Pearson 1991 ; P. Lesica, pers. comm.). It seems likely that these sites are very marginal, and/or 

 that the individuals were found while dispersing from a nearby high quality site. 



Other habitat descriptions of 5. b. chapmani trapping sites in the northern Rocky Moimtains 

 have sometimes included mention of sphagnum moss (Layser and Burke 1973, Groves and 

 Yensen 1989) while others have not (Wilson et al. 1980). I captured a single juvenile male 

 lenmiing on a dry alpine/subalpine ridge in northeast Washington (Wilson et al. 1980). 



Areas with extensive moss mats, particularly sphagnum, are the most likely sites in which to 

 find new bog lemming populations in Montana. Other habitats in Montana may either support 

 lower densities of bog lemmings; be used primarily by dispersing individuals; be used during 

 specific seasonal, climatic, or competitive situations; or be population sinks. Marginal habitats 

 and areas may be important to maintain population viability. The only certainty is that there is 

 much to be learned about habitat use by northern bog lemmings. 



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