Relative use of xeric boreal habitats by shrews (Sorex spp.)

Few studies have explicitly examined habitat use by shrews (Sorex spp.) in the boreal forest of western North America. We conducted pitfall trapping in six common xeric habitat types in Yukon, Canada, to determine their relative use by shrews. The overall capture rate was 0.47 shrews per 100 trap nights (TN), with a total sampling effort of 3652 TN. Cinereus shrews (Sorex cinereus; 0.25 per 100 TN) were the most common species, followed by dusky shrews (Sorex monticolus; 0.14 per 100 TN) and American pygmy shrews (Sorex hoyi; 0.08 per 100 TN). Shrew capture rates and species richness was low in all habitat types sampled. Cinereus shrews were captured in similar numbers in boreal mixedwood forest and alpine shrub habitats, and rarely in other lowland forest habitat types. Dusky shrews were captured largely in alpine shrub habitats, while pygmy shrews were captured only in lowland forest habitat types. The relative use of alpine shrub habitat by cinereus shrews and dusky shrews was not expected. Our data was limited by low captures; however, we provide a first approximation of the relative use of common forest types and subalpine shrub habitat in the boreal forest of northwestern Canada.

High Prevalence of Borrelia mayonii (Spirochaetales: Spirochaetaceae) in Field-Caught Tamias striatus (Rodentia: Sciuridae) From Northern Wisconsin

Borrelia mayonii is a recently discovered bacterial spirochete that causes Lyme disease and is transmitted by the blacklegged tick, Ixodes scapularis Say (Acari: Ixodidae). To date, B. mayonii has been isolated from two vertebrate host species in Minnesota: field-caught white-footed mice (Peromyscus leucopus Rafinesque; Rodentia: Cricetidae) and American red squirrel (Tamiasciurus hudsonicus Erxleben). Here, we describe the first detection of B. mayonii in field-caught eastern chipmunks (Tamias striatus L. (Rodentia: Cricetidae)) from northern Wisconsin. During our study, we captured 530 unique small mammals and found an infection prevalence of 23.50% in field-caught eastern chipmunks (4/17) and 1.19% in Peromyscus spp. (5/420). Mean larval and nymphal burdens were determined for captured Blarina brevicauda (0, 0), Glaucomys volans (0.29, 0.14), Myodes gapperi (0.27, 0), Napaeozapus insignis (0, 0.25), Peromyscus spp. (1.88, 0.11), T. striatus (1.06, 0.65), and Sorex cinereus (0.09, 0). The high B. mayonii infection prevalence in eastern chipmunks suggests that the species may be an important reservoir for B. mayonii in the Upper Midwest.

Changes within Small Mammal Communities since the 1988 Huckleberry Mountain Fire

This study is a continuation of investigations conducted at Huckleberry Mountain to determine the effect of the 1988 Greater Yellowstone fire on the small mammal community, and document changes in this community over the 22 years since this natural disturbance. Previous research was conducted in 1993, 1994, 1997, and 1998 and we sampled the same communities in 2009 and again in 2010 using the identical sampling methodology. During the summer of 2010 we live trapped 252 Southern Red-backed Vole (Myodes gapperi), 57 North American Deermouse (Peromyscus maniculatu), 22 Least Chipmunk (Tamias minimus), 12 Western Jumping Mouse (Zapus princeps), four Montane Vole (Microtus montanus), one Northern Pocket Gopher (Thomomys talpoides), four Cinereus Shrew (Sorex cinereus), and five Dusky Shrew (S. monticolus). These results are similar to our results from 2009 and corroborate findings from other investigations indicating early dominance of P. maniculatus in burned forests and M. gapperi in control unburned areas. M. gapperi and P. maniculatus accounted for the majority (87%) of captures. In addition more M. gapperi were found in control sites than P. maniculatus, and as the burned habitat recovers over time, the relative numbers of P. maniculatus are decreasing, and the number of M. gapperi are increasing, suggesting that the burned habitats are returning to a more natural pre-disturbance community structure. However, community diversity indices (which include all mammal species and their relative proportions) suggest that there are still considerable differences between burned and unburned sites. Despite the numbers of voles and deermice changing over time (as predicted), the burned and control small mammal communities are still quite different from one another even after 22 years.