| Summary: | Small mammals play important roles in Wisconsin ecosystems; however, considering their importance and ubiquity, we know little about the best way to capture them or how to distinguish between cryptic species. Additionally, we do not have consistent information regarding distributions and habitat requirement of many small mammal species. This study was broken into 4 parts in order to address these knowledge gaps. When evaluating richness and diversity of small mammal communities it is important to consider the impact that trap efficacy may have on these indices. The objectives of my study were to determine species specific trap efficacy relative to Sherman traps and pitfall traps, assess the impact of trap efficacy on measures of species richness and diversity, and compare mortality rates between trap types, and if pitfall covers reduce trap mortality. In the summers of 2009 and 2010, I trapped throughout Wisconsin in 5 habitats. I used 180 transects (190 m-long) of 20 Sherman live traps spaced every 10 m and 10 pitfall traps spaced every 20 m for 4 consecutive nights. I trapped 3,261 small mammals of 22 species in 34,235 trap nights. Pitfall traps were more effective at capturing shrews and voles, whereas Sherman traps captured more mice (Peromyscus spp.) and squirrels. Irrespective of habitat type, both trap types together captured significantly higher species richness and diversity than either trap type independently. Covers significantly reduced mortality for Peromyscus spp., but not for voles or shrews and covers reduced overall captures of voles. My results indicate that Sherman and pitfall traps capture different portions of the small mammal community and, regardless of the habitat type, should be used in combination when assessing species richness and diversity. In Wisconsin, white-footed mice (Peromyscus leucopus noveboracensis) and woodland deer mice (P. maniculatus gracilis) are difficult to distinguish. Recent climatic trends have facilitated encroachment of P. leucopus north into the range of P. maniculatus, making unambiguous species identification imperative. Cranial and external measurements have been used previously to differentiate these species. However, since large geographic morphological variation occurs and most previous studies used measurements from deceased specimens, definitive morphological measurements need to be identified that can quickly and effectively classify live Wisconsin Peromyscus spp. in the field. I live trapped Peromyscus spp. in central and northern Wisconsin during the summer of 2010. I measured ear, tail, hindfoot, and weight from live animals and collected tissue for genetic confirmation. In addition to using mDNA analysis to identify samples to species, I collected measurements from 84 P. maniculatus and 293 P. leucopus in 6 Wisconsin counties. I used discriminate function analysis (DFA) to develop equations to identify characteristics that best separated mice to species. By using ear length alone, 97.9% of the samples could be correctly classified with most P. leucopus <17mm and most P. maniculatus ≥ 17mm. By adding weight to the function, I was able to achieve 99.2% classification accuracy and with the addition of tail was able to achieve 99.5% differentiation. The arctic shrew (Sorex arcticus) and American water shrew (S. palustris) are wide-spread boreal species. Sorex arcticus reaches its southern distribution in Wisconsin and within the Midwest S. palustris also reaches its southern range extent in Wisconsin. Although the ranges of both species are generally thought to occur in the Driftless Area in the southwestern portion of Wisconsin, no occurrences have been documented from the region. Within the past decade and half, the known distribution of these species has changed dramatically. I used museum records and geo-referenced surveys to remap the known distribution of S. arcticus and S. palustris in Wisconsin. Herein, I report records of S. arcticus and S. palustris within the Driftless Area and extend the distribution of S. arcticus and S. palustris south of their former range, including the most southerly extant record of S. arcticus. This study emphasizes the continued value of voucher specimens and museum collections. Determining small mammal species habitat associations and environmental characteristics, important in site occupancy, are central to understanding species biology and community organization. During the summers of 2009 and 2010, I trapped small mammals and measured habitat variables throughout the state of Wisconsin at 180 sites spanning 13 natural habitats. I captured 3,261 individual small mammals of 22 species, allowing for characterization of small mammal communities within natural habitats. I was also able to model occupancy for 12 species using habitat covariates while incorporating imperfect detection. Comparisons among small mammal communities indicated that organization was based on soil moisture, abundance of trees, and climate. Additionally, the most important covariates in predicting small mammal occupancy were basal area, frequency and duration of wet periods, and minimum winter temperature. The ability to detect differences in community similarity and species occupancy, based on climate, is likely a product of the large geographical extent of this study, underscoring the need to assess community structure at multiple scales. Given the importance of climate in structuring these small mammal communities, predicted warming winter temperatures could have considerable impacts on small mammal communities in the region. Interestingly, occupancy of the meadow jumping mouse was best predicted by the presence of precipitation before a trap check and availability of pitfall traps. These conclusions would have been missed using other analyses that do not account for imperfect detection. Finally, my results indicate that soil moisture, abundance of trees, and climate are important for species occupancy and, at the community level, these variables create regular and predictable community structure across a heterogeneous landscape. Wisconsin Department of Natural Resources (Bureau of Endangered Resources), Prairie Biotic Research, Inc., and the University of Wisconsin – Stevens Point.
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