A Comparison Study of the Ecological Distribution of Small Mammals in Southwestern North Dakota

The objectives of this study were to survey the small mammal fauna from eight habitats typical of southwestern North Dakota and to determine the habitat preference of the species found. Fifteen species were collected and grouped according to their occurrence in areas of varying vegetation densities. Four species (Reithrodontomys megalotis, Microtus penn- sylvanicus, Sorex cinereus, and Eutamias minimus) were collected in dense vegetation. R. megalotis and M. oennsylvanicus were most abundant and exhibited preferences for cottonwood bottomlands and lowland meadows. S_. cinereus was also limited to lowland meadows, while Eh minimus occurred primarily in brushy coulees. Areas of moderate vegetation density were preferred by four species (Microtus ochrogaster, Citellus tridecem- lineatus, Onychomvs leucogaster and Mus musculus). M. ochrogaster inhabited similar but drier sites to those preferred by M. pennsylvanicus. C. tridecemlineatus, 0. leucogas ter and M. musculus were generally collected along fence lines. However, M. musculus was also collected in granaries. Dry upland prairie and sagebrush areas were regarded as sparse vegetation, and were preferred by Dipodomys ordii and Peroqnathus fasciatus. Furthermore, D. ordii occurred only in sandy areas, while P_. fasciatus was less specific in its preferences. Four species of bats were collected in the vicinity of Amidon. These included Myotis lucifugus, M. leibii, Eptesicus fuscus and Lasiurus borealis. Peromyscus maniculatus was collected in every habitat sampled, and was considered to be non-selective in its habitat preference. P. m. nebrascensis was most abundant; some specimens were identified as P^. m. luteus. No specimens were identified as P_. m. bairdii or P. leucopus ariduius, and if present they were considered to be rare. Treatment of bait with an insect repellent reduced bait loss, but also appeared to reduce crapping success