Cooperative Fish and Wildlife Research Units Program: Wyoming
Education, Research and Technical Assistance for Managing Our Natural Resources

Grassland habitats and the species that occupy them have become the focus of tremendous conservation concern range-wide due to widespread loss, fragmentation, and conversion to non-native monocultures (Brennan and Kuvlesky 2005, WGFD bird and mammal grassland plan). Less than 4% of pre-human settlement North American grasslands remain intact (Samson and Knopf 1994). As a result, many small mammal species that utilize grassland habitats are classified as Species of Greatest Conservation Need (SGCN) in the State Wildlife Action Plan (WGFD 2010) (Table 1). A critical informational need is how small mammal abundance, diversity and productivity are altered when native prairies are converted to non-native systems dominated by species such as cheatgrass (Bromus tectorum). SGCN small mammals that occur in Wyoming grasslands (Table 1) help shape vegetative communities by serving as seed predators and dispersers (Vander Wall 1993, Bass et al. 2006, Bricker et al. 2010). Moreover, evidence suggests that small mammals are particularly vulnerable to habitat changes such as those caused by exotic grass invasion because of their short longevity and complete dependence on the local environment for food (Sammon and Wilkins 2005, Hanser and Huntly 2006, Richardson 2010). The dispersal and establishment of exotic grasses in eastern Wyoming will likely only increase as previously contiguous tracts of grasslands are fragmented by increasing wind and oil and gas exploration and extraction. 1) Examine and compare small mammal abundance, diversity, reproductive status, sex ratios, population age structure, productivity, and morphometrics in native mixed-grass prairie compared to areas with exotic grass (cheatgrass) encroachment. 2) Quantify vegetative characteristics of native and exotic grasslands that benefit grassland SGCN mammals. 3) Conduct a removal experiment of the deer mouse, a common generalist species that can thrive in human-altered environments, to determine grassland small mammal SGCN habitat preferences and quality in areas with native versus non-native grasses in the absence of the dominant species. 4) Compare the efficacy of multiple techniques (Sherman and Havahart live-traps and pitfall traps) for sampling grassland small mammal populations. 5) Develop recommendations for grassland management in eastern Wyoming based on the results from objectives 1-2.