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Case Study <br />In our continuing research in northeastern Kansas, we investigate the effects of <br />habitat fragmentation on the rodent species within a 29.6-acre (12-ha) successional <br />old-field (Foster and Gaines 1991). Since 1984, the vegetation has been maintained <br />by mowing to produce archipelagos (Figure 1). Each archipelago consists of one <br />large patch (5,980.0 ydz = 50 x 100 m), or 6 medium patches (each 344.5 yd'- <br />12 x 24 m), or 15 small patches (each 38.27 yd' = 4 x 8 m). We view the large <br />patches as controls with no fragmentation. The archipelagos of medium and small <br />patches represent increasing levels of fragmentation. The areas between archipelagos <br />are mowed every two weeks during the growing season and are assumed to be <br />unsuitable habitat. Total area of suitable habitat is 4.7 acres (approximately one- <br />sixth of the original field). The rodent community consists of species that range in <br />body size from large cotton rats (Sigmodon hispidus), with adults weighing at least <br />4.13 ounces (118 g), to intermediate prairie voles (Microtus ochrogaster), weighing <br />at least 0.87 ounce (25 g). Adults of the two smallest species, deer mice (Peromyscus <br />maniculatus) and western harvest mice (Reithrodontomys megalotis), weigh at least <br />0.64 ounce (18 g) and 0.25 ounce (7 g), respectively. <br />Biological diversity on the small patches is lower than on the large patches because <br />cotton rats are not resident there (Foster and Gaines 1991, Gaines et al. 1992). All <br />species are distributed among habitat types relative to their body sizes, such that <br />cotton rats have highest densities on the large patches, prairie votes have highest <br />densities on the medium patches, and deer mice and western harvest mice have <br />0 o d o 0 <br />0 <br />0 0 0 <br />0 ? 0 <br />0 0 0 0 0 <br />0 0 0 0 0 <br />M a o a o <br />0 0 0 0 0 <br />0 <br />0 0 0 0 0 <br />G G O n o <br />0 0 0 0 0 <br />0 <br />0 0 <br />0 0 <br />109 yards (100 meters) <br />Figure I. Study site showing archipelagos. <br />256 ? Trans. 57" N. A. Wildl. & Nat. Res. Conf. (1992)