IMPACT ON RODENTS OF MOWING STRIPS IN OLD FIELDS OF EASTERN KANSAS
NORMAN A. SLADE*
Natural History Museum & Biodiversity Research Center and Department of Ecology & Evolutionary Biology, 1345 Jayhawk Boulevard, University of Kansas, Lawrence, KS 66045-7561, USA
To minimize impact on small mammals while preventing invasionof woody vegetation, we mowed alternating 15-m strips on our area. We then compared numbers and movements of 5 species of rodents on mowed and unmowed strips. Numbers of hispid cotton rats (Sigmodon hispidus) and prairie voles (Microtus ochrogaster) were reduced temporarily in the mowed strips, whereas numbers of white-footed mice (Peromyscus leucopus), deer mice (P. maniculatus), and westernharvest mice (Reithrodontomys megalotis) did not change signiﬁcantly. Movements of cotton rats, prairie voles, and harvest mice across mowed strips were reduced, whereas movements within unmowed strips were relatively unaffected, decreasing only for white-footed and harvest mice in 1 of 2 temporal replicates. Changes in numbers and movements were of short duration, and hence mowing narrow strips whenvegetation could recover rapidly had little sustained impact on this rodent community.
Key words: Sigmodon abundance, disturbance, habitat fragmentation, Microtus, movements, Peromyscus, Reithrodontomys, rodents,
Habitat disturbance is potentially disruptive to mammalian populations, yet periodic mowing or burning may be necessary to maintain early successional vegetation that some mammalsprefer or require. In northeastern Kansas, hispid cotton rats (Sigmodon hispidus) can be quite abundant in disturbed vegetation (e.g., old ﬁelds and roadsides). However, cotton rats are less common in brushy or woody areas and are not found in mature eastern deciduous forest, the climax vegetation of the area. As part of a long-term study of population dynamics of cotton rats and associated smallmammals, we mowed our study area at 2- to 5-year intervals to prevent the invasion of woody vegetation. In early summer, immediately after mowing the grid (except for hedgerows) to a height of 15 cm, deer mice (Peromyscus maniculatus) and white-footed mice (P. leucopus) were the only species that were common. As the growing season progressed and grasses and forbs recovered, we captured cotton rats,prairie voles (Microtus ochrogaster), and western harvest mice (Reithrodontomys megalotis—Swihart and Slade 1990). From 1975 to 1991, we mowed only when cotton rats were at low population densities, but occasionally this dictated that we delay mowing 1 or more years. In 1995–1996 and 1999–2000, we mowed half of the study area, alternating mowed and unmowed 15-m strips in 1
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year and reversing the treatments the following year. Our intent was that the unmowed strips would serve as habitat refugia, thus minimizing disruption to rodent populations. We found only 2 studies of undisturbed strips as refugia for small mammals. Strip thinning of pulp trees in Minnesota reduced bird density in theshort, but not long, term and increased numbers of small mammals (Christian et al. 1996). Darveau et al. (2001) found no signiﬁcant differences in densities of southern red-backed voles (Clethrionomys gapperi) and P. maniculatus in intact forests and riparian zones, thinned or not, interspersed with clear-cuts in Quebec. Undisturbed strips interspersed with clear-cuts or mowed strips have not alwaysprovided refugia in other taxa. Spiders maintained normal abundance and species diversity in unmowed strips within hayﬁelds in Hungary, but these populations did not provide sufﬁcient dispersers to maintain diversity in interspersed mowed strips (Samu 2003). Grassland birds in Iowa survived and reproduced better in partially harvested ﬁelds of switchgrass (Panicum virgatum) than in completely...