Small Mammal Populations of the Principal Agricultural Crops in North-Central Kansas

Seven habitats were sampled from March through October 1991. Five study sites (alfalfa, grain sorghum, winter wheat, corn, and soybean) represented the principal agricultural crop types of Kansas. The remaining two study sites, a fencerow bordered by smooth brome (Bromus inermis) and an upland pasture, comprised the non-cropland habitats. Each habitat was trapped at least once a month; however, sites in which perturbations occurred were sometimes sampled more often, depending upon the number of disruptions. Study sites were compared on the basis of species richness, species diversity, evenness, and similarity. Differences among seasons and in the crop rotation and/or vegetative condition at study sites also were examined to ascertain their effects on the relative density and species diversity of small mammal populations within and among sites. Effects of agricultural perturbations were tested to determine significance by comparing the relative densities of select small mammal species before and after each disturbance. Generally, agricultural perturbations showed no effect on small mammal abundances, although, harvest altered relative densities in a few instances. Ten species of small mammals were represented among the seven study sites. Of the ten, Peromyscus maniculatus (deer mouse) was by far the most abundant, dominating all habitats. The deer mouse was a permanent resident at all sites, except the upland pasture site, which held no resident rodent species. During the study, small mammals were most common from late spring through the end of summer. P. maniculatus was most abundant during late spring and early fall, whereas Onychomys leucogaster (northern grasshopper mouse) reached its highest abundance in mid-summer through early fall Chaetodipus hispidus (hispid pocket mouse) was absent from all habitats until mid-summer and disappeared in early fall. The remaining rodent species were not present in high enough densities to make generalizations regarding trends in abundance. Habitat breadth values (BH) calculated for each small mammal species represented indicated that P. maniculatus, O. leucogaster, Reithrodontomys megalotis (western harvest mouse), and possibly C. hispidus, were habitat generalists. The winter wheat site exhibited the highest species diversity and species richness of all the study sites, whereas the upland pasture possessed the lowest values of these parameters. The corn and alfalfa sites were most similar, while the upland pasture versus the alfalfa and soybean sites were most dissimilar.