Academic journal article The American Midland Naturalist

Communities of Small Mammals in Six Grass-Dominated Habitats of Southeastern Oklahoma

Academic journal article The American Midland Naturalist

Communities of Small Mammals in Six Grass-Dominated Habitats of Southeastern Oklahoma

Article excerpt

ABSTRACT.-During autumn 1991, we sampled small mammals in six grass-dominated hal> itats including upland ungrazed native prairie, upland improved pastures, upland mowed native prairie, upland roadside fencerows, lowland ungrazed native prairie and lowland ungrazed native prairie with forbs and shrubs in southeastern Oklahoma. Eleven species of small mammals were represented in 405 captures. Species diversity (H') was high in upland (1.57) and lowland (1.47) ungrazed prairie and least for upland fencerows (0.86). Evenness (J') exhibited a similar pattern and was high in upland (0.88) and lowland (0.82) ungrazed prairie and least for lowland ungrazed prairie with forbs and shrubs (0.53). Community overlap (R^sub o^) varied from 1.00 (upland improved pastures and upland roadside fencerows) to 0.57 (upland improved pastures and upland ungrazed prairie). Abundance of small mammals was greatest in fencerows, largely due to the prevalence of hispid cotton rats (Sigmodon hispidus). Different land-use practices elicited both positive and negative species-specific responses. Current human activity in some locations may produce habitat mosaics that result in an overall greater abundance and diversity of small mammals.

INTRODUCTION

Abundance and distribution of mammals in Oklahoma have been influenced markedly by humans (see Caire et al., 1989), especially by the conversion of native grasslands to rowcrop agriculture since European settlement. Bowles (1981) reported that over 50% of the species of mammals in Iowa have been reduced in numbers or have been extirpated from the state. Similarly, Kaufman and Kaufman (1989) discussed a decrease in species richness and diversity of mammals in Kansas due to farming. However, response by individual species of small mammals to human activity often is species specific. For example, populations of deer mice (Peromyscus maniculatus) have responded positively to the conversion of grasslands to cropfields (e.g., Kaufman and Kaufman, 1990), mowing for hay (e.g., Sietman et al., 1994), grazing of livestock (e.g., Phillips, 1936; Grant et al., 1982; Clark et al., 1989) and burning of grasslands (e.g., Kaufman et al., 1990). In contrast, populations of western harvest mice (Reithrodontomys megalotis) have been reduced in cultivated areas (Kaufman and Kaufman, 1989; Bowles and Copsey, 1994) and frequently burned prairie (Kaufman et al., 1988).

Previous studies also have documented changes in community structure of small mammals due to agricultural practices. Species diversity was reduced by grazing of sagebrush habitats (Reynolds, 1980; Reynolds and Trost, 1980) and cultivation of grassland habitats (Kaufman and Kaufman, 1989), whereas species diversity was increased by moderate grazing of tallgrass prairie sites in Colorado (Moulton et al., 1981). In contrast, Hall and Willig (1994) found no significant differences in species diversity among small mammal communities using Conservation Reserve Program (CRP) grasslands and shortgrass prairie.

The primary objective of our study was to assess variation in the communities of small mammals among six grass-dominated habitats in southeastern Oklahoma. We predicted that communities of small mammals would differ among the six grasslands due to species-specific responses to various land-use practices. Furthermore, we expected that species diversity of small mammals would be highest in the least altered and lowest in the most altered habitats. We present data concerning species-specific differences in use of grassland habitats, variation in species diversity and evenness among habitats, and community overlap between habitats.

METHODS

Study sites.-Small mammals were trapped in six different grasslands in Bryan Co., Oklahoma, including upland ungrazed native prairie, upland improved pastures, upland roadside fencerows, upland mowed native prairie, lowland ungrazed native prairie, and lowland ungrazed native prairie with forbs and shrubs. …

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