Abstract

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Bruns Stockrahm, D.M. 1995. Ecology of the northern grasshopper mouse (Onychomys leucogaster) and prairie vole (Microtus ochrogaster) in Clay county, Minnesota. Final report submitted to the Minnesota Department of Natural Resources. 98 pp.

Abstract:

During the summers of 1994 and 1995, study sites in Clay County, Minnesota, were live-trapped for small mammals with the main objective of studying the ecology of the northern grasshopper mouse (Onychomys leucogaster) and the prairie vole (Microtus ochrogaster) in grassland habitats. In 1994, 8 sites were studied including sites at Bluestem, Felton, and Bicentennial Prairies, Buffalo River State Park, and Ames Gravel Quarry (T141N, R46W, S36). Quite a few prairie voles were trapped at Bicentennial Prairie (n = 23) and a few were trapped at Ames Gravel Quarry (n = 5), but northern grasshopper mice were not captured on any of the sites during 1994. During our 1995 field season, we intensified our trapping efforts and concentrated our efforts on Ames Gravel Quarry where we had captured northern grasshopper mice in the past. We also retrapped Bicentennial Prairie in the area where we had captured prairie voles in 1994. During 1995, we were successful at capturing both prairie voles (n = 17) and grasshopper mice (n = 5) at Ames Gravel Quarry and prairie voles (n = 8) at Bicentennial Prairie. Prairie voles were associated with dense grass cover and a considerable layer of grass litter. Therefore, we suggest that prescribed burns be kept relatively small and carried out on a rotational basis. This would provide at least some nearby unburned areas to which the prairie voles could escape and find suitable grass litter cover. Grasshopper mice were assocated with sandy "hillocks" which we defined as the sandy spoil piles or topsoil piles left from previous excavations at the quarry. Weedy vegetation often grew on these hillock areas. One adult male and 1 adult female mouse at Ames Gravel Quarry were fitted with radiocollars and released at the location of capture. Although the female lost her radiocollar within the first few days, we radiotracked the male from 17 August to 7 September 1995. Radiotelemetry position readings were taken during daytime and nighttime hours. We found that he was strictly nocturnal and after sunset, he left his burrow and moved about, often traveling great distances. He paused periodically in his forays, and we assumed he was stopping to feed. He returned to his burrow prior to sunrise. We think that excavation activities could be planned in advance to minimize the danger to the grasshopper mice. Hillocks in the area of a planned excavation could be searched in advance and flagged if burrow systems appeared present. Because the northern grasshopper mouse seems to be limited in its distribution, has specific habitat requirements (i.e., sandy hillocks), and sparsely populates an area due to its extremely large home range, we suggest that it be considered for inclusion on Minnesota's List of Special Concern Species. A wide variety of nontarget species were also captured during the study. Most notably, we captured meadow jumping mice (Zapus hudsonius) at Ames Gravel Quarry for the first time in Clay County since we began our small mammal studies in 1990. Small mammal diversity was quite high at Ames Gravel Quarry, probably due in part to the great heterogeneity of the habitat.

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