Summer Food Habits of Microtus Ochrogaster and Sigmodon Hispidus

Abstract

Stomach contents were analyzed for 97 Microtus ochrogaster haydenii and 86 Sigmodon hispidus texianus to determine what plant species were utilized, the effect of plant availability on diet, and the degree to which both species utilized identical foods. Based on per cent volume consumed, Sigmodon utilized Triticum aestivum, Kochia scoparia, Sporoholus asper, Bromus japonicus, Rumex crispus, and Xanthium commune the most during June and July from two areas. In the same areas, Microtus concurrently found S. asper, K. scoparia, Bouteloua gracilis, B. japonicus, R. crispus, and Digitaria sanguinalis the most palatable. Availability of plants was found to be an influencing factor on what was eaten, but certainly was not the only factor, because many plant species that were not dominant were seemingly selected on the basis of their growth stage and palatability. Although the same species of plants comprised most of the food eaten by the two rodents, it is likely that competition existed for space rather than food, as ample food was available throughout the study.