Feeding Preferences of the Prairie Vole (Microtus ochrogaster) for Seeds and Plants from an Old-Field Successional Community

Free-choice preference tests were performed in the laboratory to evaluate the response of the prairie vole (Microtus ochrogaster) to particular plant species. Plant material was collected during three summer months in 1989 on a 12 ha experimental area in eastern Kansas undergoing secondary succession. For each month, preference indices were calculated for plants. Seeds were tested for palatability and preference in the spring of 1989. Although prairie voles have no preference with respect to most plants on the succession area, Helianthus annuus was strongly preferred whereas Ambrosia artemisiifolia, Alcaphyla rhomboidea, Apocynum cannabinum, Erigeron spp. , Rumex crispis, Solanum carolinense, Toralis arvensis and Hypericum punctatum were all strongly avoided. The process of secondary succession in an old-field community involves temporal changes in plant and animal species. After initial establishment of the plant community, herbivorous animals may colonize the area. The broad definition of herbivore is used to include granivores (seed eaters) and folivores (stem and leaf eaters). As the plant community undergoes successional changes, primarily from annual to perennial plants that characterize the surrounding climax vegetation, the animal communities may also change. Traditionally, ecological succession in a temperate zone old-field has been examined by studying the plant communities and developing models to explain the changes in plant species composition in the different series of succession (Crawley, 1983). The role of herbivorous mammals in influencing succession has not been as closely examined; evidence does suggest that herbivorous mammals, such as microtine rodents, do have an influence on the structure of plant communities (Batzli and Pitelka, 1970). Herbivorous mammals can influence succession depending on a number of factors, such as the rate of population growth, feeding preferences, and the intensity of predation by the herbivores. This content downloaded from 157.55. 39.199 on Tue, 21 Feb 2017 20:04:50 UTC All use subject to http://about.jstor. org/terms 4 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE Our research on small mammal feeding preferences is part of a long-term study of successional dynamics in an old-field community (Foster, 1989). In this study several aspects of succession are considered, including the association of herbivorous mammals with successional changes in the plant community. Foster (1989) reported that the dominant rodent species at the site were prairie voles (Microtus ochrogaster), hispid cotton rats (Sigmodon hispidus), western harvest mice (Reithrodontomys megalotis), and deer mice (Peromyscus maniculatus). The prairie vole was selected to study food preferences since it had the highest densities on the site. If there were any impact on the plant community, it would most likely be the result of this microtine rodent. Prairie voles have diets composed of grasses, forbs, and some small amounts of insects, bark, seeds, fruits and tubers (Batzli, 1985). Although microtine species in general are associated with grasslands, the prairie vole has been found to include a high proportion of forbs in its diet (Batzli, 1985). Thus, old-field areas undergoing succession that contain a mixture of grass and forb species offer suitable habitat for prairie voles. Within this environment, prairie voles may have preferences for particular plant species. In a study in western Kansas, prairie voles exhibited preferences for specific plants in a mixed community (Fleharty and Olsen, 1969). A study of food habits of the prairie vole in an area adjacent to the study site found that many different forbs and grasses were eaten in captivity (Menhusen, 1963). In the old-field succession area, preferential mammalian herbivory by the prairie vole may affect the rate of succession depending upon the particular species that was preferred. The first step in testing this hypothesis is to determine whether prairie voles have feeding preferences for specific plants in an area undergoing secondary succession. MATERIALS AND METHODS Study site. The study site is located 16 km north of the University of Kansas on the John H. Nelson Environmental Study Area. A detailed description of this study is in Foster (1989). The 12 ha site is bordered on the north by a brome field dominated by Bromus inermis. The north-east corner and east side are bordered by an oak-hickory fencerow and farm. The west and south edges are bordered by a dirt road that separates the field from an oak-hickory woodland. The study site has been used for wheat and soybean production from 1980 to 1984. After the last wheat crop was harvested in June 1984, the field was abandoned for an experimental study on the effects of patch size on the rate of succession. In July 1984 the field was mowed into patches of vegetation that ranged in size by two orders of magnitude. The sizes were: large (5000 m sq.), medium (288 m sq.), and small (32 m sq.). This pattern was maintained by mowing every other week from April to October. This content downloaded from 157.55. 39.199 on Tue, 21 Feb 2017 20:04:50 UTC All use subject to http://about.jstor. org/terms VOLUME 94, NUMBERS 1-2 5 Table 1. Median preference indices during summer 1989. Values are based on 10 replicates.